3.

Human Anatomy
3.1. History of Human anatomy
The term ‘anatomy’ is Greek in origin. It takes its root from ‘ana’ and
‘tome’ (ana-up ; tome-cutting). Thus anatomy is the science of physical
structure of an animal or plant studied by dissection. The Human Anatomy
provided the necessary knowledge for surgery and medicine.
The study of human anatomy dates back to 2500 BC, when the
Egyptians prepared mummies. They removed internal organs of cadavers be-
ing mummified. They also did surgery for wounds and broken bones. In India
during 500 - 491 BC Susruta performed cataract operation. In 1st century AD,
Celsus, a Roman physician wrote about surgical procedures.
The year 1543 AD was significant due to publication of an accurate
book on Anatomy by Andreas Vesalius. In 1628 William Harvey described the
functioning of heart and the movement of blood in animals. These earlier works
were followed by the discovery and accurate account of each and every or-
gan system and organs in human body. In the recent times, attempts are being
made to understand the molecular architecture in every cell of our body.

Gray’s Anatomy
Eventhough several books had been written on Human
Anatomy, a monumental work titled ‘Anatomy : Descriptive and
Surgical by Henry Gray is unique in its discriptions. The first
edition of this book was published in August 1858. It is in print
continually for the past 145 years. A more elaborate 38th edition
was published in the year 2000.
Henry Gray was born in Windsor, London in 1827. He
lived upto 1861. He was a brilliant medical student at St. George’s
Hospital, London.

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3. 1. 1 The Integumentary System
The word integument means covering. The integumentary system cov-
ers the outside of the body. It protects internal structures, prevents the entry
of infectious agents, reduces water loss, regulates body temperature, produces
vitamin D and detects stimuli such as touch, pain and temperature. Since the
integument performs several functions, it is commonly referred to as Jack of
all trades.
The skin or integument rests on layers of cells called hypodermis.
The hypodermis attaches the skin to underlying bones and muscles. It supplies
blood vessels and nerves to the skin.

hair
sebaceous gland

epidermis

arector pili (smooth

muscle)
hair follicle dermis
nerve
blood vessels sweat gland
fat
hypodermis

Fig.3.1.1. Skin and hypodermis

The skin is composed of two major tissues, namely dermis and

epidermis. The dermis is mostly formed of connective tissue having fibro-
blasts, adipose cells and macrophages. It provides the structural strength to
the skin. The dermis accommodates nerve endings, hair follicles, smooth muscles
and glands.
It is divided into two layers, namely the superficial papillary layer
and deeper reticular layer. The papillary layer has projections called papil-
lae. The reticular layer is the major layer of the dermis. It is dense in nature.
It is continuous with the hypodermis.
Epidermis :- The epidermis is made up of stratified squamous epithelium. It
is separated from the dermis by a basement membrane. It contains mel-
105
anocytes giving colour to the skin. Many of the cells of the epidermis produce
a protein substance called keratin. Hence they are called as keratinocytes.
keratin
stratum corneum

stratum lucidum
stratum granulosum
stratum spinosum
stratum basale

papilla

basement membrane
Fig.3.1.2. Epidermis
The deepest layers of the epidermis produce nerve cells by mitosis.
As new cells are formed, the older cells are pushed to the surface. The sur-
face cells will protect the inner new cells. Gradually the shape and chemical
nature of the surface cells will get altered. Slowly they get filled with keratin.
This process is called keratinization. During this process the epidermis gets
divided into five distinct regions or strata. They are the stratum basale, stra-
tum spinosum, stratum granulosum, stratum lucidum and stratum cor-
neum.
Stratum basale is in the deeper region of the epidermis. It consists of
one layer of columnar cells. Keratinization of cells begins in this region. Above
this layer stratum spinosum is seen. It has 8-10 layers of polygonal cells.
The stratum granulosum is the next upper layer. It has 3-5 layers of flat-
tened cells. Above this layer stratum lucidum occurs. It is a thin zone having
several layers of dead cells. The top most layer is called the stratum cor-
neum. It consists of more than 20 layers of dead cells. These cells get filled
with keratin. They are said to be cornified. The cornified cells are surrounded
by a hard protective envelope.
The skin can be either thick or thin. All five epithelial layers are seen
in the thick skin. However stratum corneum contains more number of cells.
Thick skin is formed in the soles of the feet, the palms of hands and tips of
fingers. The general body surface has thin skin. In the thin skin each epithe-
lial layer inturn has few layers of cells. There are only one or two layers of
cells in stratum granulosum.
106
Callus :- The regions of skin subjected to constant friction or pressure are
thickened to form the callus. The callus has several layers of cells in the
stratum corneum.
Skin colour :- The colour of the skin is due to pigments in the skin. The
thickness of the stratum corneum and blood circulation can also cause skin
colour. Normally the colour is caused by the pigment melanin. It provides
colour to skin, hair and eye. It protects the body from sun’s ultraviolet rays.
Melanin is produced by melanocytes. Melanin production is genetically deter-
mined. However, hormones and exposure to light can also alter the colour.
Skin dervatives
Hair :- The hairs are integumentary structures. A hair has a root and a shaft.
While the shaft projects above the skin, the root remains well below the sur-
face. The base of the root has a hair bulb. It is an expanded region. The shaft
and most of the root of the hair are formed of dead keratinized epithelial cells.
These are arranged in three concentric layers called the medulla, the cortex
and the cuticle. The central axis of the hair is formed of the medulla. Major
part of the hair is formed of a single layer of cells.

medulla

cortex hair

cuticle

internal epithelial root sheath

external epithelial root sheath
dermal root sheath

Fig.3.1.3. Cross section of a hair within a follicle

According to the amount and types of melanin, the hair colour may
vary. The colour of the hair is genetically determined. During old age the
amount of melanin decreases causing white hair. Grey hair has a mixture of
faded, unfaded and white hairs.
The hair growth is due to addition of cells at the base of the hair root.
The growth stops at specific stages. After a resting period, new hair replaces
old hair. The hairs on the head grow for a period of three years and rest for
1-2 years.
107
 The muscle cells found associated with hair follicles are called the
arrector pili. Contraction of these muscles cause ‘goose flesh’ making the
hairs to ‘stand on end’.
The skin has sebaceous glands and the sweat glands. The seba-
ceous glands are located in the dermis. They produce an oily substance called
the sebum. These glands are connected by a duct to the upper part of the hair
follicles. The mammary glands are the modified sweat glands.

glandular lobe

nipple lactiferous duct

fat

Fig.3.1.4. The mammary gland

The most common type of sweat gland on the skin are the merocrine
glands. They are simple coiled tubular glands. They open directly on to the
skin through sweat pores. The gland has two parts. They are the deep coiled
portion and the duct which passes to the surface of the skin. The number of
sweat glands are more in the palms of the hands and soles of the feet.
Nails :- Each nail is made up of two parts. They are the nail root and the nail
body. The nail body is the visible part. The nail root is covered by the skin.
The proximal and lateral edges of the nail are covered by nail fold.

free edge
nail body hyponchium nail bed
nail groove nail root
nail fold
lunula
eponchium
nail root

dorsal view longitudinal section

Fig.3.1.5. Nail

108
 The stratum corneum of the nail fold grows onto the nail body as the
eponchium. The free edge of the nail body is the hyponchium. The nail is
found placed on the nail matrix and nail bed. A small white region seen at the
base of the nail is the lunula. It contains the nail matrix. The nails grow at an
average rate of 0.5-1.2 mm per day.

3.2. Skeletal system

The skeletal system is constituted by bones, cartilages and ligaments.
This system provides ‘the shape’ to the body. Further, bones remain as re-
gions for the attachment of muscles. It also helps to hold weight. Structures
like skull, protect inner organs. This system is also useful in locomotion. The
bones remain as reservoirs of fat and certain minerals. The bone marrow is
the site for the production of erythrocytes.
skull

mandible
clavicle
scapula
sternum
ribs
humerus
vertebral column
ulna
coxa
sacrum radius
carpals
metacarpals
phalanges

femur

patella

tibia
fibula

tarsals
metatarsals
phalanges
Fig.3.2.1. The complete skeleton
109
 The bones can be long, short, flat or irregular in shape. Hands and legs
have long bones. Short bones are broad in shape. Carpals (wrist bones)
and tarsals (antkle bones) are shorter. Flat bones are thin and flattened. Skull
bones, ribs, sternum and scapula (shoulder blade) are flat bones. Verterbral
and facial bones are irregular in shape.
Structure of a typical long bone
A bone is covered by a double layered sheath called the periosteum.
The outer layer of the periosteum is fibrous in nature. It is a dense collag-
enous layer having blood vessels and nerves.
A growing long bone has three regions. The long bony part is the dia-
physis or shaft. It is made up of compact bone.

head
neck articular cartilage
epiphysis
epiphyseal plate

cancellous bone
compact bone
periosteum
body diaphysis
medullary cavity
endosteum

patellar groove
Fig.3.2.2. Long bone - Femur or thigh bone

The end of the bone consists of epiphysis. It is made up of spongy

bone. The outer surface of epiphysis is formed of compact bone. In between
the epiphysis and diaphysis epiphyseal or growth plate is found. It is made
up of hyaline cartilage. Growth in length of bone occurs at this plate.
The cavity inside the diaphysis is called the medullary cavity. This
cavity is lined by a membrane called the endosteum. The cavity inside the
diaphysis in adults contain yellow marrow. It is mostly adipose tissue. The
medullary cavity of the epiphysis contains red marrow concerned with blood
cell formation.
110
 Dried, prepared bones are used to study skeletal anatomy. The bones
are named according to their position in the body. The named bones are di-
vided into two categories: (1) the axial skeleton and (2) the appendicular
skeleton. The axial skeleton consists of the skull, hyoid bone, vertebral col-
umn and thoracic cage. The appendicular skeleton consists of the limbs and
their girdles. In human body, there are 206 bones, of these 80 are in the axial
skeleton, 126 in the appendicular skeleton. Among the bones of the axial
skeleton 28 bones are in the skull, 26 bones in the vertebral column, 25
bones in the thoracic cage and one remains as the hyoid bone. (details as
found below)
Axial skeleton - It forms the upright axis of the body. It protects the brain,
the spinal cord and the vital organs found within the thorax.
a) Skull - The human cranial capacity is about 1500 cm 3. It consists of 22
bones. It protects the brain. It supports the organs of vision, hearing, smell
and taste. The lower jaw or mandible remains specially attached to the skull.
The skull or cranium is covered by eight bones. They are one pair each of
parietal and temporal, individual bones as frontal, sphenoid, occipital and
ethmoid. These bones are joined by sutures to form a compact box like struc-
ture. The sutures are immovable joints.

frontal bone

parietal bone
eye orbit
sphenoid bone
nasal bone
temporal bone

zygomatic bone

maxilla

mandible

Fig.3.2.3. Skull

111
 suture
frontal bone

parietal bone
sphenoid bone
nasal bone
occipital bone

zygomatic bone
temporal bone
maxilla

mandible
Fig.3.2.4. Skull - Lateral view

In the front there are 14 facial bones. Of these maxilla, zygomatic,

palatine, lacrymal, nasal and inferior nasal koncha remain as pairs.
Mandible or lower jaw and vomer are unpaired bones .
The parietal and occipital bones are major bones on the posterior
side of the skull. The parietal bones are joined to the occipital bone at the
back. The side of the head is formed of the parietal and the temporal bones.
The large hole in the temporal bone is the external auditory meatus. This
opening is meant for transmitting sound waves towards the eardrum. On the
lateral side immediately anterior to the temporal, the sphenoid bone is seen.
Anterior to the sphenoid bone is the zygomatic bone or cheek bone. It is a
prominent bone on the face. The upper jaw is formed of the maxilla. The
mandible constitutes the lower jaw.
The major bones seen from the frontal view are the frontal bone,
zygomatic bone the maxillae and the mandible. The most prominent open-
ings in the skull are the orbits and the nasal cavity. The two orbits are meant
for accommodating the eyes. The bones of the orbits provide protection for
the eyes and attachment points for the muscles that move the eyes. The bones
forming the oribits are the frontal, sphenoid, zygomatic, maxilla, lacrymal,
ethmoid and palatine. The head region also contains 6 ear ossicles. They
are Maleus (2), incus (2) and stapes (2).
112
 A large opening found at the base of the skull is the foramen
magnum. Through this opening the medulla oblongata of the brain descends
down as the spinal cord.
b). Vertebrae - The vertebrae make up the slighty S-shaped vertebral
column or backbone. The vertebral column consists of 26 bones. They are
divided into 5 regions. They are the cervical (7), thoracic (12), lumbar (5),
sacral (1) and coccygeal (1) vertebrae.
first cervical vertebra (atlas)
second cervical vertebra (axis)

Cervical region

intervertebral disc

Thoracic region
intervertebral foramina

spinous process

transverse process

Lumbar region

sacrum
Sacral and coccygeal region

coccyx

Fig.3.2.5. Vertebral column

113
Vertrebra - Structure : The main load - bearing portion of a vertebra is a
solid disc of bone called the centrum. The centra of adjacent vertebrae are
separated by intervertebral discs of cartilage. Projecting from the centrum
dorsally is a vertebral arch. It encloses the neural canal. This canal contains
the spinal cord. Several bony projections are seen on the vertebral arch. On
each side of the centrum ther are two transverse processes. On the dorsal
side there is a neural spine. These bony projections are used for attachment
of muscles. Further, there are two superior and two inferior processes meant
for articulation with the neighbouring vertebra.

rib
spinous process
transverse process
body
vertebral foramen
vertebral arch
transverse
body(centrum) process
spinous
intervertebral body
process
body(centrum)
intervertebral foramen
Fig.3.2.6. Vertebra
The first cervical vertebra is the atlas. It balances and supports the
head. It has no centrum. The second is the axis. The sacral vertebrae are
fused. They form a triangular structure called the sacrum. The coccygeal
vertelera has no function. It is a vestige. During development in the embryonic
stage there are nearly 34 vertebrae present. Of these, 5 sacral bones are
fused to form a single sacral bone. 4 or 5 coccygeal bones are fused to form
a single coccyx.

sacrum

coccyx
Fig.3.2.7. Sacrum and coccyx
114
c). Rib cage - There are 12 pairs of ribs. Each articulates with a thoracic
vertebra. In the front, the first ten pairs are attached to the sternum (breast
bone) by costal cartilages. The first seven are attached directly to the ster-
num. They are called the true ribs. Cartilages of 8th, 9th and 10th ribs are
fused and attached to 7th. They are called the false ribs. 11th 12th pairs are
not attached to the sternum. They are called floating ribs.

clavicle 1st thoracic vertebra

scapula
sternum humerus

xiphoid process costal cartilage

12 thoracic vertebra
th

Fig.3.2.8. Rib cage

Appendicular skeleton
It consists of the bones of the upper and lower limbs and the girdles
by which they are attached to the body.
Pectoral girdle - The hands are attached to the pectoral girdle. Both of them
are attached loosely by muscles to the body. This arrangement facilitates free-
dom of movement. Hence it is possible to place the hand in a wide range of
positions.

acromion process

glenoid fossa

Fig.3.2.9. Scapula

115
 The pectoral or shoulder girdle consists of two pairs of bones. Each
pair has a scapula or shoulder blade and a clavicle or collarbone. The scapula
is a flat, triangular bone. A glenoid fossa is located in the superior lateral
region of the scapula. It articulates with the head of the humerus. The clavicle
is a long bone. It has a slight S-shaped curve. It can be easily seen and felt.
The clavicle holds the upper limb away from the body.
clavicle

scapula

humerus

ulna

carpals radius

metacarpals

phalanges

Fig.3.2.10. Skeleton of the arm

Pelvic girdle or pelvis - It is a ring of bones formed by the sacrum and

paired bones called the coxae or hip bones.

ilium
sacrum

acetabulum pubis

ischium

Fig.3.2.11. Pelvis

116
 Each coxa is formed by the fusion of three bones, namely ilium,
ischium and pubis. A fossa called the acetabulum is located on the lateral
surface of each coxa. The acetabulum is meant for the articulation of the
lower limbs.
pelvis

femur

patella

tibia
fibula

tarsals
metatarsals
phalanges
Fig.3.2.12. Skeleton of the leg wih pelvic girdle

Upper limb or hand - The part of the upper limb from shoulder to the elbow
is the arm. It contains one long bone called the humerus. The head of hu-
merus articulates with the glenoid fossa of the scapula. The distal end of the
bone articulates with the two forearm bones.

Fig.3.2.13. Femur

Forearm - This part of the hand is in between the arm and the wrist. The
forearm has two bones. They are the ulna and the radius. While the ulna is
on the side of the little finger, the radius is on the lateral or thumb side of the
forearm.
117
Wrist - This short region is composed of eight carpal bones. These are
arranaged into two rows of four each. The carpals along with accompanying
ligaments are arranged in such a way that a tunnel on the anterior surface of
the wrist called the carpal tunnel has been formed. Tendons, nerves and
blood vessels pass through this tunnel to enter the hand.
Hand - The bony framework of the hand is formed of five metacarpals.
They are attached to the carpals in the wrist. The concave nature of the palm
in the resting position is due to curved arrangement of metacarpals.

carpals

metacarpals

phalanges

Fig.3.2.14. Hand

Each hand has five digits. They include one thumb and four fingers.
Each digit has small long bones called phalanges. While the thumb has two
phalanges other fingers have three each.
Lower limb or Leg : The general pattern of the lower limb is similar to that of
the upper limb.

bone
fibrous capsule
articular cartilage
synovial fluid

Fig.3.2.15. A Synovial joint

118
 The upper region of the leg is the thigh. It contains a single longest
bone called the femur. It has a prominent rounded head for articulating with
the acetabulum of the pelvic girdle. The distal end of the femur has two condyles
for articulation with the tibia.
The knee region has a large, flat bone called the patella. It articulates
with the patellar groove of the femur.
Leg - The leg is that part of the lower limb between the knee and the ankle. It
consists of two bones namely, the tibia and the fibula. The tibia is larger and
it supports most of the weight of the leg.
Ankle : The ankle consists of seven tarsal bones. The ankle articulates with
the tibia and the fibula through the talus.
Foot : It is formed of metatarsals and phalanges. They correspond to the
metacarpals and phalanges of the hand.
Joint
All bodily movements are caused by muscles. Our skeletal muscles
are firmly attached to bones. Movements involving such muscles cause pull
on our bones. Hence movements need movable bone joints.
A joint or an articulation is a place where two bones come together.
All joints are not movable. Many joints allow only limited movements.
The joints are named according to the bones that are united.
Kinds of joints - There are three major kinds of joints. They are the fibrous,
cartilaginous and synovial joints.
Fibrous joints - In this type, the joints are united by fibrous connective tis-
sue. There is no joint cavity. These joints show little or no movement. Sutures
formed between cranial bones, a syndesmosis (to bind) between radius and
ulna are examples for this type.
Cartilaginous joints - These joints unite two bones by means of either hya-
line cartilage (synchondroses) or fibrocartilage (symphyses). The articula-
tion between the first rib and the sternum is an example for syncondrosis.
Symphysis pubis and intervertebral discs are examples for symphyses.
Synovial joints - These joints contain a synovial fluid. This fluid is a com-
plex mixture of polysaccharides, proteins, fats and cells. It forms a thin lubri-
cating film covering the surfaces of a joint. Elbow and knee joints are of this
type.
119
3.3. Muscular System
Locomotion and bodily movements are characteristic features of the
animals. The movements are effected by various cell organelles such as cilia,
flagella and organs like muscles. Muscular movements are more powerful and
energetic. The skeletal muscles apart from their role in smarter movements,
provide beautiful shapes to the body. The inner smooth muscles of the visceral
organs make them work like machines all through the life period. The muscle
cells function like small motors to produce the forces responsible for the move-
ment of the arms, legs, heart and other part of the body. Thus the highly spe-
cialized muscle tissues are responsible for the mechanical processes in the
body.
Based on structure, functioning and occurrence three different types
of muscle tissues have been identified. They are the skeletal, visceral and
cardiac muscles.
1). Skeletal muscles or striped muscles : These muscles are attached to
the bones. The muscle cells are long and cylindrical. These voluntary muscles
cause body movements.
2). Visceral muscles or Nonstriated muscles: These are found in the walls
of the inner organs such as blood vessels, stomach and intestine. The muscle
cells are spindle shaped. These are involuntary in nature.
3). Cardiac muscle : These are found in the wall of the heart. The muscle
cells are cylindrical and branched. The muscles are involuntary in nature.
Skeletal muscles.
The skeletal muscles are attached to bones by tendons. The tendons
help to transfer the forces developed by skeletal muscles to the bones. These
muscles are covered by sheets of connective tissue called fascia.
Tendons : These are connective tissue structures showing slight elasticity.
They are like cords or straps strongly attached to bones. The tensile strength
of tendons is nearly half that of steel. A tendon having 10 mm diameter can
support 600 - 1000 kg.
Fascia : These are assemblages of connective tissues lining skeletal muscles
as membranous sheets. The fascia may be superficial or deep. The superficial
fascia is a layer of loose connective tissue found in between skin and muscles.
The deep fascia are collagen fibres found as a tough inelastic sheath around
the musculature. They run between groups of muscles and connect with the
bones.
120
Shapes of muscles.
There is a wide variety of shapes and sizes in muscles. Based on
general shape and the orientation or muscle fibres in relation to the direction
of pull, they can be grouped into two classes.
1. Parallel : These muscle fibres are parallel to the line of pull. The muscles
may be flat,0.0ienwuadri fleneran olonges andtraphe kell. Thindividualle fibreru ono thriei arlengthne ot T

121
Distribution of muscles
I. Muscles of the head
There are two groups of muscles. They are craniofacial and masti-
catory muscles. The craniofacial muscles are related to eye orbital margins,
eyelids, nose, nostrils, lips, cheeks, mouth, pinna, and the scalp. These muscles
are also known as muscles of facial expression. Among these muscles those
that are related to the lip movement are significant. The facial expression is
mostly due to lip movement and positioning of the lips. Such thought related
movements are caused by several muscles associated with lips and the skin
around the mouth. Since orbicularis oris and buccinator muscles provide
lip movement for kissing posture they are known as “kissing muscles”. Smil-
ing is accomplished by zygomasticus major and minor, levator anguli oris
and risorius. The muscles of the lips can also provide expressions such as
sneering and frowning. The chin dimples are located between the mentalis
muscles
aponeurosis
auricular muscles
pars frontalis
orbicularis oculi
pars occipitalis
levator labii
zygomaticus muscles

orbicularis oris masseter

sternocleidomastoid
mentalis

platysma

Fig.3.3.1. Muscles of the Head

The masticatory (or speech) muscles move the mandible of the

lower jaw. The muscles responsible for this movement are masseter
temporalis and pterygoid. Tongue movements are caused by intrinsic and
extrinsic muscles. Swallowing of food is facilitated by several muscles re-
lated to the mouth, roof of pharynx, uvula and other regions.
II. Muscles of the Neck region.
The movements of the neck region are caused by cervical, suprahy-
oid, infrahyoid and vertebral muscles.
122
III. Muscles of the Trunk region.
The muscles of the vertebral column help to bend and rotate the body.
These are strong back muscles that help the trunk to maintain erect posture.
The most prominent muscles of this region are the erector spinae, longissi-
mus and spinalis.
Four important thoracic muscle groups are associated with the pro-
cess of breathing. While the process of inspiration is due to scalene and ex-
ternal intercostal muscles, the expiration is performed due to internal
intercostals and transverse thoracis. Major breathing movement is due to
diaphragm, a curved musculofibrous sheet that separates thoracic and ab-
dominal cavities.
Abdominal muscles can aid in forced expiration, vomitting, defaecation,
urination and childbirth.
The inferior opening of the pelvic bone is covered by pelvic dia-
phragm muscles. Below these muscles perineum is pressent. The perineum
and other “subfloor” muscles form the urogenital diaphragm. Pelvic and
urogenital diaphragm may get strecthed in pregnancy due to weight of the
foetus. However by specific exercises they can be strengthened.
trapezius

deltoid
pectoralis major

biceps serratus anterior

brachii

abdominis

Fig.3.3.2. Muscles of the Trunk

123
IV. Muscles of the upper limb.
The hands are attached to the pectoral girdle and to the vertebral
column by large conspicuous muscles such as trapezius, rhomboid major
and minor, levator scapulae and lattissimus dorsi.
The trapezius is a flat, triangular muscle. It extends over the back of
the neck and upper thorax. It maintains the level and poise of the shoulder. It
helps to rotate the scapula forward, so that the arm can be raised above the
head. It helps to bend the neck backwards and laterally.
Latissimus dorsi is a large flat triangular muscle. It is a conspicu-
ous muscle stretching over the lumbar region and lower thorax. This muscle is
useful in adduction, extension and medial rotation of the humerus. It helps in
the backward swinging of the arm. By raising the arm above the head it helps
to pull the trunk upwards and forwards. It is useful in violent expiratory activi-
ties such as coughing or sneezing. It helps in deep inspiration.
Serratus anterior and pectoralis major connect the ribs to the
scapula. Pectoralis major extends from the upper thorax and abdomen to act
on the humerus. It is a fan shaped muscle. It spreads between the clavicle and
the 7th costal cartilage in the front of the chest. It helps to swing the extended
arm forward and medially. It helps in climbing. It is active in deep inspiration.
rectus
The muscles of the upper arm are the coracobrachialis, biceps,
triceps and brachialis. The coracobrachialis arises from the coracoid bone
in the shoulder and ends in the humerus of the upper arm. It helps to move the
arm forward and medially. The biceps brachii is a large fusiform muscle. It
has two proximal heads for attachement. They are connected to the coracoid
and shoulder joint. The lower head ends in the radius of the lower arm. It is a
powerful muscle causing flexing of the hand. The triceps arises by three
heads from scapula and upper part of humerus on the posterior side. The
wrist, hand and finger movements are caused by several extrinsic and intrin-
sic hand muscles. A detailed study of them could be made in higher classes.
V. Muscles of the lower limb.
Thigh movements are caused by anterior, postereolateral and deep
muscles. The anterior muscles are the iliacus and psoas major which help to
flex the thigh. The gluteus maximus form the mass of the buttocks region.
Leg movement is caused by the anterior thigh muscles, quadriceps femoris
and sartorius. The sartorius is the longest muscle of the body. It runs from
the hip to the knee. Muscle movement of ankle foot and toe are caused by
several groups of extrinsic and intrinsic muscles. A detailed study of them
could be made in higher classes.
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3. 4. Digestive system
The process of nutrition in man is holozoic. In this type of nutrition,
the nutrients are made available to the body through digestion of food. In
digestion, the macromolecules or biopolymers of food are hydrolysed to yield
their corresponding monomers. This process is facilitated by enzymes. Thus
the digestive system comprises the alimentary canal, associated glands and
regions of absorption of food. The digestive tract comprises various organs
from mouth to anus.

oral cavity (mouth)

pharynx

oesophagus

liver
gall bladder stomach
pancreas

small intestine
large intestine

appendix anus

Fig.3.4.1. Digestive system

Mouth or Buccal cavity
The opening of the oral cavity is bounded by the lips. The lips are
muscular folds covered internally by mucosa. The lateral walls of the oral
cavity are the cheeks. The inner walls of the cheeks are lined by moist strati-
fied squamous epithelium. The lips and cheeks are useful in the process of
mastication and speech.

125
Tongue - It is a large muscular organ. It is attached to the floor of the oral
cavity. The anerior part of the tongue is free. A thin fold of tissue called the
frenulum attaches the free end to the floor of the mouth. The tongue is di-
vided into two parts by a groove called the terminal sulcus. About two thirds
of the anterior surface is covered by papillae. Some of them contain taste
buds.
Teeth - There are 32 teeth in the mouth of a human adult. These are called as
permanent teeth. There are 4 different types of permanent teeth seen. This
nature is known as heterodontism. The types of teeth are incisors(8), ca-
nines(4), premolars(8) and molars(12). Since the teeth in the right and left
side of the mouth are mirror images of each other, the dental arrangement is
represented as follows.

i 2/2 : c 1/1 : pm 2/2 m 3/3 X 2 or

incisor
canine
I premolar
upper jaw
II premolar
I molar
× II molar
III molar

lower jaw

Fig.3.4.2. Dentition

Each tooth consists of three regions. These are the upper crown,
middle neck and basal root regions. The crown region has one or more cusps.
The tooth is made up of a calcified tissue called dentine.
The dentine of the tooth crown is covered by an extremely hard sub-
stance called enamel. The surface of the dentine in the root is covered with a
bonelike substance called cementum. It helps to anchor the tooth in the jaw.
In the centre of the tooth there is a pulp cavity. This cavity is also called as
the root canal. This canal contains blood vessels and nerves. The canal opens
at the base through apical foramen.
126
 The teeth are set in sockets along the edges of the upper and lower
jaws. This region of the jaw is covered by dense fibrous connective tissue and
stratified squamous epithelium. It is called as the gingiva.
enamel

crown
dentine

neck

pulp cavity with nerve and

blood vessels

root cementum

root canal
Fig.3.4.3. A tooth apical foramen

Salivary glands : These are scattered throughout the oral cavity. Three pairs
of glands are larger. They are the parotid, submandibular and sublingual
glands. The Parotid glands are the largest. They are located just anterior to

parotid gland parotid duct

submandibular gland sublingual gland

Fig.3.4.4. Salivary glands

the ear on each side of the head. The submandibular glands are found on
the inferior borders of the mandible. The sublingual glands are the smallest.
They lie immediatly below the mucous membrane in the floor of the mouth.
There are other numerous small, coiled, tubular glands in the mouth. They are
the lingual (tongue), palatine(palate), buccal and labial(lips) glands.
127
Pharynx : A description of pharynx is provided under respiratory system.
Oesophagus : This part of the digestive tube extends between the pharynx
and the stomach. It is about 25 cm long. It lies in the mediastinum of the
thorax, anterior to the vertebra and posterior to the trachea. It passes through
the diaphragm and ends at the stomach. The oesphagus has thick walls. The
inner wall is lined by a moist stratified squamous epithelium. The upper and
lower ends of this tube have sphincters to regulate the movements of mate-
rials.
Stomach : It is an enlarged sac like structure. This sac found in the upper part
of the abdomen is horizontally placed. It is divisible into two regions namely
cardiac and pyloric stomachs. The cardiac stomach is towards the left of the
abdomen. The oesophagus opens into the cardiac stomach through the gas-
troesophageal or cardiac opening. A part of the stomach to the left of the
cardiac region is the fundus. The largest part of the stomach is the body. The
body narrows to form the pyloric region. The pyloric opening between the
pylorus and intestine is surrounded by a ring of muscles called the pyloric
sphincter.

oesophagus
fundus
gastroesophageal opening
cardiac region
body
pyloric opening

pyloric region

Fig.3.4.5. Section of the stomach

Small intestine : It consists of three parts: the duodenum, the jejunum and
the ileum. The entire small intestine is about 6m. long.
Duodenum - It is about 25 cm. long. It curves within the abdominal cavity
and completes nearly 180 degree arc. Liver and pancreas are associated
with the duodenum.
Jejunum and ileum- The jejunum and ileum are 2.5m. and 3.5m in length
respectively. These two are similar in structure to the duodenum. However
128
there is a gradual decrease in the diameter of the small intestine. The junction
between the ileum and the large intestine is the ileocaecal junction. It has a
ring of smooth muscles forming a sphincter, and a one way ileocaecal valve.
Liver : It is the largest visceral organ. It weighs about 1.36 Kg. The liver
consists of two major left and right lobes, and two minor lobes caudate and
quadrate. The bile secreted by the liver gets collected in the gall bladder.
There are two hepatic ducts and they unite to form a single duct. The com-
mon hepatic duct is joined by the cystic duct from the gall bladder to form the
common bile duct. It empties into the duodenum.
Gall bladder : It is a sac like structure on the inferior surface of the liver. It
is about 8 cm long and 4 cm wide.

liver
gall bladder

pancreas

common bile duct pancreatic duct

hepatopancreatic
ampulla
duodenum

Fig.3.4.6. Duodenal region

Pancreas : It is a compelx organ. It is composed of both endocrine and exo-

crine tissues. The endocrine part of the pancreas consists of pancreatic is-
lets. They produce insulin and glucagon. The exocrine part of the pancreas
consists of acini. They produce digestive enzymes. The pancreas consists of
several lobules. The ducts from the lobules unite to form the pancreatic
duct. It joins the common bile duct at the hepatopancreatic ampulla.
Large intestine.
Caecum : It is the proximal end of the large intestine. At this region large, and
small intestines meet. The caecum is about 6 cm in length. Attached to the
caecum is a small blind tube about 9 cm long. It is called the vermiform
appendix.

129
Colon : It is about 1.5 - 1.8 m long. It consists of four parts namely the
ascending colon, transverse colon, descending colon and sigmoid co-
lon. The sigmoid colon extends into the pelvis and ends at the rectum.
Rectum : It is a straight, muscular tube that extends from the sigmoid colon to
the anal canal.
Anal canal : It is the last 2cm of the digestive tract. It ends at the anus. The
canal has two sphincters, namely the internal anal sphincter and the external
anal sphincter.

3. 5 Respiratory system
The process of respiration involves movement of air in and out of the
lungs, gas exchange between air in lungs and the blood, transport of O 2 and
CO2. These processes are facilitated by working together of well developed
respiratory organs and the circulatory system.
The respiratory organs include nasal cavity, pharynx, larynx, tra-
chea, bronchi and lungs. These organs are organised into upper and lower
respiratory tracts.
Upper respiratory tract.
nasal cavity
external nose

uvula
nasopharnyx
oropharynx

laryngopharynx
epiglottis

oesophagus trachea

Fig.3.5.1. Upper Respiratory tract

1. Nasal cavity : The nasal cavity follows the external nose. The nose is a
visible prominent structure. Internally it is supported by cartilage plates. The
bridge of the nose is formed of the nasal bones and extension of the skull

130
bones(frontal and maxillary). The respiratary passage is divided into two cham-
bers by a median partition. The nasal passage opens to the outside through
external nostrils. It opens inside by internal nostrils at the pharynx.
2. Pharynx : The buccal cavity and the nasal passage open into the pharynx.
It is a common pathway that opens into the oesophagus of the alimentary
canal and larynx of the respiratory system.
The pharynx is divided into three regions, namely the nasopharynx,
the oropharynx and the laryngopharynx.
The nasopharynx extends from the internal nostril to the region of
the uvula. The uvula is a soft outgrowth hanging in between the posterior part
of the oral cavity and the pharynx. It prevents the entry of food into the nasal
cavity. The wall of the nasopharynx is lined by ciliated columnar epithilium.
The middle ear opens into the nasopharynx through two auditory tubes. This
arrangement is meant for equalizing the air pressure between the atmosphere
and the middle ear. The inner surface of the nasopharynx also contains the
pharyngeal tonsil or adenoid meant for defence against infections. An
enlargement of the tonsil can interfere with breathing.
The oropharynx remains between the uvula and the epiglottis. The
oral cavity opens into the oropharynx. Near the opening of the oral cavity 2
sets of palatine tonsils and lingual tonsils are present.
The laryngopharynx extends in between the epiglottis and the
oesophagus.
3. Larynx : The larynx is seen just behind the pharynx and the buccal cavity.
This region is surrounded by cartilages(3 unpaired and 6 paired). These are
interconnected by muscles and ligaments.
The unpaired cartilages are the thyroid, cricoid and epiglottis. The
thyroid cartilage is the largest. It is also known as the Adam’s apple.

epiglottis
hyoid bone
thyrohyoid membrane
thyroid cartilage
cricoid cartilage

cartilage rings
Fig.3.5.2. Larynx

131
The cricoid cartilage forms the base of the larynx. The other cartilages are
placed above the cricoid. The epiglottis is attached to the thyroid. It projects
as a free flap over the opening of the larynx. It prevents food particles from
saentering into the tracheal tube.
The ligaments inside the larynx form the vocal folds or vocal cords.
The vocal cords and the openings between them are called the glottis. The
vocal cords are involved with sound production. The air moving past the vocal
cords make them to vibrate. Louder sounds are made by increasing the ampli-
tude of vibrations. Frequency of the vibrations can be altered by changing the
length of the vibrating segments of the vocal cords. The length is altered by
muscles attached to the cartilage. Males usually have longer vocal cords than
females. The sound made by the vocal cords can be altered by the tongue, lips
and teeth to form words.
4. Trachea (or wind pipe) : It is a membranous tube. The wall is made up of
connective tissue and smooth muscles. The wall is provided support by 15-20
‘C’ shaped cartilage rings. They protect the trachea and keep it open all the
time.
The inner wall of the trachea is lined by mucous membrane. It con-
sists of ciliated columnar epithelium. The cilia of this epithelium help to propel
mucus and foreign particles towards the larynx.
The length of the trachea is 10-12 cm. Its inner diameter is 12 mm.
The trachea extends from the larynx to the level of the 5th thoracic vertebra.
The basal part of the trachea divides to form 2 smaller tubes called the pri-
mary bronchi (sing : bronchus). The cartilage ring found at the basal region is
called the carina. Foreign objects reaching carina stimulate a powerful cough
reflex.
4. Lungs : The pair of lungs are the actual organs of respiration. Each lung is
conical in shape. The base of the lung rests on the diaphragm. The right lung
is larger than the left and it weighs around 620g. The left lung weighs 560g.
The right lung has three lobes and the left lung has two.
The lungs are placed within the thoracic cavity. Each lung is sur-
rounded by separate pleural membrane. The region inside the pleural mem-
brane is named as the pleural cavity. This cavity is filled with pleural fluid.

132
 Larynx
trachea

carina
primary bronchus
pleura
secondary bronchi branchioles

Fig.3.5.3. Lungs
The region in between the two lungs is named as the mediastinum.
It is a midline partition, being occupied by the heart, trachea and oesophagus.
Structures such as the primary bronchi, blood vessels, nerves and
lympatic vessels enter or exit the lungs at a specific region on the inner margin
of the lungs. This region is known as the hilum. All structures passing through
the hilum are referred to as the root of the lung.
The primary bronchi on entering into each lung divide further into
secondary bronchi. There are two secondary bronchi in the left lung and
three in the right lung. The secondary bronchi inturn give rise to tertiary bronchi.
They divide still further and finally give rise to bronchioles. The diameter of
the bronchioles is less than 1 mm. These bronchioles divide several times to
become still smaller terminal bronchioles.
Like the trachea, the primary bronchi are supported by ‘C’. shaped
cartilages and smooth muscles. As the bronchi become smaller the cartilages
are replaced by smooth muscles.
The terminal branchioles end in small air filled chambers called al-
veoli. The alveoli are thin walled pouches. They collectivelly provide the res-
piratory surface for gaseous exchange. The wall of the alveolus is very thin
providing a minimal barrier to gaseous exchange between air and blood. The
thickness of the wall of the alveolus is as little as 0.05m. Studies have shown
that in human lungs there are about 300 million alveoli. They provide a mean
total alveolar surface area value of 143 m 2.

133
5.Thoracic wall and muscles of respirations.
Eventhough the lungs are the principal organs of respiration, the pro-
cess of ventilation happens by an indirect method. Air pressure gradients be-
tween thoracic chamber and lung cavity due to thoracic enlargement and re-
duction cause ventilation of lungs. Thoracic modifications during respiration
happen due to several muscles. These are called the muscles of inspiration
and expiration. These muscles are the diaphragm, external and internal
intercostal muscles between the ribs, pectorals and scalene (Ref. Muscu-
lar system).

3. 6. The Circulatory System

The multicellular organisation in animal world has resulted in the ori-
gin and evolution of circulatary system in animals. This arrangement facili-
tates internal transport of various substances to all organs and organ systems.
Among majority of multicellular animals this system remains as a closed type.
It has blood running inside closed blood vessels, the blood being pumped by
heart. In man, as in all mammals there is a double circulation of blood. The
primary circulation through pumping action of heart, supplies blood to all re-
gions of the body. The blood later returns to the heart. It is called the
systemic circulation or body circulation. A similar circulation carries blood
to lungs for oxygenation and returns it back to the heart. It is called the pul-
monary circulation.
tissue capillaries

lung capillary

left side of heart

right side of heart
arteries

veins

tissue capillaries

Fig.3.6.1. Systemic and Pulmonary circulations

134
Systemic and Pulmonary circulations
The most important component of this system is the heart. It is a
large, muscular, valved structure having four chambers. The chambers are
the right atrium, left atrium, right ventricle and left ventricle. Each atrium
opens into a corresponding ventricle. The right and left chambers are sepa-
rated by septa.
Systemic circulation :- The left atrium receives oxygenated blood from the
lungs, through the pulmonary vein. When the atria contract, blood from the
left atrium is forced into the left ventricle. Later by a contraction of the ven-
tricle, the blood leaves the heart through the aorta. The aorta is the single
systemic artery emerging from the heart. By successive branchings, the aorta
gives rise to hundreds of arteries taking blood to all regions of the body. As the
branchings happen, the arteries divide into numerous (4 × 106) arterioles. In
the target organs they produce four times as many capillaries. A similar num-
ber of venules converge into each other forming veins of increasingly larger
size. Finally, only two veins, the superior and inferior vena cavae return the
blood to the right atrium. Thus the course of blood from left ventricles through
the body organs and back to the atrium forms the systemic circulation.
Pulmonary circulation :- The venous blood from right atrium is conducted to
the right ventricle. The ventricle expels the blood via the pulmonary trunk to
the lungs. The oxygenated blood later returns by the pulmonary veins to the
left atrium. This circulation from right ventricle to the left atrium via the lungs
is termed the pulmonary circulation.
Portal circulation :- In the systemic circulation the venous blood passing
through spleen, pancreas, stomach and interstine is not carried back directly
to the heart. It passes through the hepatic portal vein to the liver. This vein
begins as capilaries from the visceral organs and ends in the liver again as
capillaries. These capillaries converge to form the hepatic vein which joins
the inferior vena cava, conveying blood to right atrium. This route is the portal
circulation.

135
Arterial system
The main arterial trunk carrying blood from the heart to the tissues is
the aorta. At its commencement it lies in the thorax, and it is known as the
thoracic aorta. Its terminal portion is in the abdomen, where it is called as
the abdominal aorta. The thoracic aorta comprises the short ascending
aorta, the arch of the aorta and the longer descending aorta. The de-
scending aorta passes downward through the diaphragm. It continues up to
the level of the fourth lumbar vertebra, where it terminates by dividing into
two common iliac arteries. The main branches of the various portions of
the aorta are as follows.
Ascending - Coronary
Right common carotid
Arch of aorta - Brachiocephalic (Innominate) Right sub clavian
Left common carotid
Left sub clavian
Visceral branches Parietal branches
Bronchial Inter costal
Esophageal Sub costal
Thoracic aorta Pericardial Superior phrenic
Mediastinal
Visceral branches Parietal branches
Coeliac
Superior mesenteric Inferior phrenic
Abdominal aorta Gonadial Lumbar
Middle suprarenal
Renal
Interior mesenteric
Terminal branches
Common iliac External iliac
Middle sacral Internal iliac

136
right common carotid artery brachiocephalic (innominate) artery

left common carotid artery

left suclavian artery

right subclavian
artery arch of aorta

ascending aorta
descending aorta

inter costal artery

right coronary artery

diaphragm
coeliac artery

superior mesenteric artery

renal artery
abdominal aorta

testicular artery

inferior mesenteric artery

left common ilac artery

Fig. 3.6.2.Human aorta and its branches

137
Ascending aorta:
The branches of the ascending aorta are the left and right coronary
arteries. They arise close to the origin of the aorta. They supply the heart
muscles with blood.
Arch of the aorta:
The branches of the aortic arch are the innominate, left common
carotid and left sub clavian arteries.
Innominate: (Brachiocephalic) this is the first branch of the aortic arch. It
passes upward and diagonally to the right and divides into two branches, the
right common carotid and the right subclavian. The common carotid
artery passes up to the neck and divides into the external carotid artery
and internal carotid artery. The external carotid artery supplies blood to
muscles, glands, skin and other structures of the face and scalp. The internal
carotid artery goes to the brain.
The right subclavian artery passes laterally to the arm. In the arm, the
subclavian artery forms the axillary arteries. The right axillary continues as
the brachial artery, which in the region of the elbow, divides into radial and
ulnar arteries. These continue in the distal portion of the arm, giving off
branches to wrist and hand.
The second branch of the aortic arch is the left common carotid
artery. It arises close to the innominate. It passes up the left side of the neck,
following a course and possessing branches similar to that of the right
common carotid. The left sub clavian artery arises from the aortic arch
independently of the left common carotid and supplies the left arum.
Thoracic aorta:
The branches of the thoracic portion of the descending aorta supply
both the internal organs and the body wall. The internal organs include
bronchi, esophagus, pericardium, lungs, rib cage and intercostal muscles.
Superior phrenic arteries (one pair) supply blood to the upper surface of
the diaphragm.
138
Abdominal aorta. This portion of the aorta has many branches. It serves
the entire lower region of the body. The following branches are given off
from the abdominal aorta.
1. The coeliac artery arises shortly behind the diaphragm, and sends
branches to the liver, gall bladder, stomach and duodenum and digestive glands
such as pancreas and liver.
2. The superior mesenteric artery, supplies the major portion of the small
intestine and a part of the large intestine.
3. The middle suprarenal arteries, supply the suprarenal glands,
4. The renal arteries supply the kidneys.
5. The internal testicular arteries in the male and ovarian arteries in the
female supply the testis and ovary respectively.
6. The inferior mesenteric artery supplies, the large intestine and rectum.
The common iliac arteries from the dorsal aorta enter into the legs.
Each iliac artery further divides into sciatic and femoral arteries supplying
blood to the leg muscles.
Pulmonary circulatory structures:
The pulmonary artery emerges from the superior surface of the right
ventricle, passes diagonally upward to the left, and crosses the root of the
aorta. It divides into right and left pulmonary arteries, branches of which
enter the right and left lungs, respectively. Pulmonary veins are four in
number, two from each Lang. They carry oxygenated blood from the lungs
to the left atrium.
Venous system:
Systemic veins are the vessels that collect blood from the tissues to
the heart. The principal systemic veins are:
1). The coronary sinus.
2). The superior vena cava.
3). The inferior vena cava and their branches and
4). The portal vein which drains the abdominal viscera.
139
 right common carotid artery left common carotid artery
right subclavian artery internal thoracic artery
brachio cephalic artery left subclavian artery
brachial artery ascending portion of aorta
descending portion of aorta
coeliac artery
superior mesenteric artery
renal artery
gonadial artery
radial artery inferior mesenteric artery
common iliac artery
ulnar artery

femoral artery

Fig. 3.6.3 Human - Arterial system

Coronary sinus:
The coronary sinus is a short vein lying on the posterior side of the
heart. It receives most of the blood from heart tissues.
Superior vena cava and its branches:
This vessel is a large venous trunk, which empties blood to the heart
from the head, neck, upper extremities and thorax. It is sounded by the union
up the right and left
Innominate (brachiocephalic) veins. It opens into the right atrium.
The principal veins draining the head and neck are the external and
internal jugular veins. The right and left subclavian veins drain the upper
extremities, each terminating at its junction with the internal jugular vein to
form the innominate vein. Near their termination form each subclavian vein

140
 internal jugular vein
R. subclavian vein external jugular vein
L. subclavian
Innominate vein
(Brachio cephalic vein)
brachial vein
superior vena cava
hepatic vein
radial vein inferior vena cava
ulnar vein ouarian (testicular) vein
renal vein
common iliac vein
internal iliac vein

femoral vein

anterior tibial vein

Fig. 3.6.4.Human - Venous system

receives an external jugular vein. Each subclavian vein inturn is formed by
the union of the cephalic and axillary vein.
Each innominate vein receives the deep cervical, vertebral, internal
mammary and inferior thyroid veins. In addition, the left innominate receives
the left superior intercostals vein and veins from thymus, trachea, esophagus
and pericardium. The subclavian veins also drain blood from the veins of the
hand (brachial)
Inferior vena cava and its branches:
This is the venous trunk which receives most of the blood from
regions of the body below the level of the diaphragm. It is the largest vein in
the body. The inferior vena cava is formed by the union of the two
common iliac veins. It extends forwards to the right of the aorta, passes
through the diaphragm and opens into the right atrium.
141
 The inferior vena cava receives blood from following veins, inferior
phrenic (from the diaphragm), hepatic (from the liver), right suprarenal (from
the adrenal gland), renal (from the kidneys), right spermatic or ovarian
(from the right testis or ovary), lumbar (from the body wall) and common
iliac (from the pelvic region) and the veins of the lower extremities.
Pulmonary circulation :- The venous blood from right atrium is conducted to
the right ventricle. The ventricle expels the blood via the pulmonary trunk to
the lungs. The oxygenated blood later returns by the pulmonary veins to the
left atrium. This circulation from right ventricle to the left atrium via the lungs
is termed the pulmonary circulation.
Portal circulation :- In the systemic circulation the venous blood passing
through spleen, pancreas, stomach and interstine is not carried back directly
to the heart. It passes through the hepatic portal vein to the liver. This vein
begins as capilaries from the visceral organs and ends in the liver again as
capillaries. These capillaries converge to form the hepatic vein which joins
the inferior vena cava, conveying blood to right atrium. This route is the portal
circulation.
Components of Circulatory system
Blood vessels
The blood vessels carrying blood away from the heart are the arter-
ies. The Veins carry blood towards the heart. The arteries and veins are
named and classified according to their anatomical position. They can also be
classified according to their size and wall structure. Functionally, arteries are
subdivided into conducting, distributing and resistance vessels.
1. Conducting vessels :- These are large arteries from the heart and their
main branches. the walls of these vessels are elastic in nature.
2. Distributing vessels :- These are smaller arteries reaching individual or-
gans. They branch into the organs. They have muscular walls.
3. Resistance vessels :- These are mostly arterioles. While these vessels
are smaller, their walls are highly muscular. Hence these vessels can reduce
pressure of blood due to peripheral resistance.

142
4. Exchange vessels :- These are the capillaries. The walls of these vessels
allow exchanges between blood and the tissue fluid surrounding the cells. The
substances commonly exchanged are oxygen, carbon-di-oxide, nutrients, wa-
ter, inorganic ions, vitamins, hormones, metabolic products and antibodies.
5. Capacitance or reservoir vessels :- These are the larger vessels and
veins. These are of varying sizes. They collect and convey blood back to the
heart. The higher capacitance of these vessels is due to their distensibility.
Hence their blood content is more, even at low pressure. The number of such
veins is also enormous.. Thus the veins are called as the “blood reservoirs”
Structure of blood vessels
The blood vessels show a vast range of structural modifications.
However a few basic patterns can be studied.
A blood vessel consists of a wall and a lumen or cavity. The wall of
the blood vessels is made up of 3 distinct layers or tunica. They are the
tunica intima, tunica media and tunica externa or tunica adventitia.

tunica adventitia
tunica media
tunica interna

elastic membrane
endothelium
(a) (b)

Fig.3.6.5. (a) Artery (b) Vein - Structural comparision

The tunica intima is formed of an endothelium, a delicate connective

tissue and elastic fibres. The tunica media contains smooth muscle cells. It
causes vasoconstriction and vasodilation. The tunica externa is composed
of connective tissue. The composition and thickness of layers varies with the
diameter of the blood vessels and the type.
Types of blood vessels
1. Large elastic arteries :- The walls of these arteries contain elastic fi-
bres. The smooth wall measures about 1micron in thickness. It gets stretched
under the effect of pulse and recoils elastically.

143
2. Muscular arteries :- There are larger and smaller muscular arteries. The
larger muscular arteries are inelastic and they have thick walls. The wall has
30-40microns in diameter in the layers of smooth muscles. Since they regulate
blood supply, they are called distributing arteries. The small muscular
arteries are capable of vasodilation and vasoconstriction.
3. Arterioles :- They conduct blood from the arteries to the capillary bed.
These are small vessels capable of vasodilation and vasoconstriction.
4. Capillaries :- These are fine vessels found between arterioles and venules.
They measure 5-8micron in diameter.
capillary endothelial cell
nucleus

Fig.3.6.6. A Capillary tube

5. Venules :- These are tubes of flat, oval or polygonal endothelial cells.

Each venule is formed by the convergence of two or more capillaries. Its
diameter ranges upto 30micron.
6. Veins :- Veins seen in anatomy are medium veins. They run in between
venules and large veins. Large veins transport blood to the heart.
Veins with diameter above 2 mm have valves. They are of semilunar
type. They allow movement of blood towards the heart. There are several
valves in the medium veins.
Branching of blood vessels :- When an artery divides into two equal branches,
the original artery ceases to exist. Hence the branches are called terminal
branches. The smaller branching vessels formed on the sides are called the
collateral branches. When arteries are joined to each other it is named as
anastomosis.
Blood supply to blood vessels :- As any other region, the cells and tissue
on the wall of the blood vessel require nourishment. Some amount can diffuse
from blood in the lumen. For vessels having diameter greater than 1 mm, dif-
fusion of nutrients may not be possible. Such vessels have very minute ves-
sels called vasa vasorum spread over them. They penetrate into the wall of
the blood vessels.
144
Innervation of blood vessels :- The walls of the blood vessels are inner-
vated by sympathetic nerve fibres. They regulate the contraction of the mus-
culature. They effect vasoconstriction.
The Heart
The heart is a hollow, fibromuscular organ. It is somewhat conical or
pyramidal in form. It is roughly the size of a closed fist. An average heart
measures 12 cm from base to the apex. Transverse diameter at its broadest
region is 8-9 cm. It is 6 cm thick antero-posteriorly. While in adult male the
heart weighs 280-340 g, in female it weighs 230-280 g.
right common carotid artery left common carotid artery
left subclavian
right subclavian artery artery
brachio cephalic artery
right atrium superior vena cava
lungs aorta
mediastinum
pulmonary artery
diaphragm left atrium

inferior vena cava

Fig.3.6.7. Location and External structure of the Heart
The thoracic organs such as heart, trachea and oesophagus form a
midline partition called the mediastinum. The heart lies obliquely in the medi-
astinum.
The heart is surrounded by a double layered membrane called the peri-
cardium. The outer layer is called the fibrous pericardium. The inner mem-
brane is called the serous pericardium. In between heart and pericardium,
there is a pericardial space. This space is filled with a fluid called the pericar-
dial fluid. aorta
pulmonary artery
superior vena cava
right atrium left atrium
pulmonary veins
semilunar valves
tricuspid valve bicuspid valve
inferior vena cava chordae tendineae
inter ventricular septum
right ventricle left ventricle

Fig.3.6.8. Internal structure of the Heart

145
 The wall of the heart is made up of three tissue layers. They are the
epicardium, myocardium and endocardium. The epicardium forms the
smooth outer surface of the heart. The middle myocardium is composed of
cardiac muscle. This layer plays an important role in the functioning of the
heart. The endocardium forms the smooth inner surface. It is formed of
squamous epithelium.

3.7. Lymphatic system

Lymphatic circulation along with blood circulation plays a key role in
maintaining the fluidity in all regions of the body. It helps to maintain fluid
balance in tissues and it absorbs fat from the digestive tract. It also functions
as body’s defence system against micro organisms and other harmful
substances. This system includes lymph, lymphocytes, lymphatic vessels, lymph
nodules, lymph nodes, tonsils, the spleen and the thymus gland.
Lymphoid cells and tissues - Lymphatic organs contain lymphatic tissues.
These tissues primarily consist of lymphocytes. They also contain macroph-
ages, dendritic cells and reticular cells. Lymphocytes are a type of white
blood cells. They originate from red bone marrow and are carried by blood to
lymphatic organs and other tissues. There are several classes of lympho-
cytes. The B-lymphocytes or B cells synthesize antibodies for recognizing
and neutralising alien macromolecules. T- lymphocytes can recognize and se-
lectively kill cells infected with viruses. B and T lymphocytes are
produced from stem cells present in the bone marrow. The T lymphocytes get
matured only after entering into Thymus, a lymphoid organ through circula-
tion. Maturation and differentiation of B cells will occur in the bone marrow
itself. Thus the thymus and bone marrow are described as central or primary
lymphoid organs.
Thymus - It is a roughly triangular, bilobed gland. It is located in the mediasti-
num (ie., between the lungs). It lies between the sternum and the pericardium.
Its size varies with age. It is largest in the early part of life (upto 15 years). At
birth it weighs 10 - 15 g. After puberty it greatly decreases in size.
Each thymus lobe is surrounded by a thin capsule made of the connec-
tive tissue. It has 2 layers. The inner layer is the medulla, the outer layer is
cortex. The lymphocytes are found only in cortex layer.
Lymph nodes - These are small round structures. Their size ranges from 1-
25 mm. They are distributed throughout the course of the lymphatic vessels.
These nodes are found all over the body. However they are concentrated as
146
aggregations in 3 regions of the body. These are the inguinal nodes in the
groin, the axillary nodes in the axillary region and the cervical nodes of the
neck.
The lymph enters the lymph nodes through afferent lymphatic vessels
and exits through efferent vessels. The nodes contain open spaces called si-
nuses. The sinuses are lined with phagocytic cells.
Spleen - It is roughly the size of a clenched fist. It is located on the left side
of the abdominal cavity. It has a fibrous capsule. The spleen contains two
types of lymphatic tissues, namely the red pulp and the white pulp.
Tonsils - These are the largest lymph nodules. They provide protection against
bacteria and other harmful materials. In adults the tonsils decrease in size and
may disappear. There are 3 groups of tonsils in the pharyngeal walls. Of the
three, the palatine tonsils are usually refered to as “the tonsils”. These are
larger lymphoid masses on each side of the junction between the oral cavity
and the pharynx. The pharyngeal tonsil or adenoid are found near the junc-
tion between the nasal cavity and the pharynx. The lingual tonsil is a loosely
associated collection of lymph nodules on the posterior surface of the tongue.

subclavian vein

thoracic duct

lymph nodes

lymphatic vessel

Fig.3.7.1. Lymphatic system

The lymphatic circulation - The lymph fluid from the tissues is drained by
lymphatic capillaries. These capillaries though present in many tissues are
absent in epidermis, hairs, nails, cornea, cartilages, CNS and bone
147
marrow. The lymphatic capillaries join into larger vessels. The larger vessels
pass to local or remote lymph nodes. These vessels and associated lymph
nodes are arranged in regional groups. Each group has its region of drainage.
Nodes within a group are interconnected. Such regional groups with nodes
and vessels are organised in (1) Head and neck (2) Upper limbs (3) Lower
limbs (4) Abdomen and pelvis (5) thorax.
The regional vessels return to the venous blood circulation via the
right and left lympho venous portals. Nearly eight lymphatic trunks con-
verge at the site of the vertebral column and open into the venous portals
nearer to the neck

3. 8. The Nervous System

A complete understanding of the human nervous system remains a
challenge. Several billion cells remain associated with this system. The vary-
ing functions of these cells and the nervous system are responsible for human
behaviour and activities. Hence, scientists from different fields collectively
are interested in understanding the functioning of this system. Studies on brain
and other related structures began several years ago. Even to-day thousands
of scientists are involved in researches for knowing the structure and func-
tioning of the brain. For a thorough knowledge of this system, further works in
anatomy, physiology, molecular,biology, psychology, medicine and other related
fields are needed.
Basically the nervous system is formed of nerve cells or neurons.
Neurons are responsible for transmission of impulses. They also help in realising,
analysing and storing messages. They can stimulate muscles to work. The
network of interconnected neurons in the nerves, brain and spinal cord have
highly complicated methods of functioning.
A neuron has a basic cell structure called the cyton. The projections
of the cyton are the dendrites and the dendrons. The inter communicating
long projection is the axon. There are variations in the shape of the cyton,
number of dendrons and nature of axon.
A neuron is interconnected with the dendrite of the neighbouring neu-
ron through the endplate of the axon. Such specialized connections are called
as synapses. In the terminal regions of the effector nerves the axon of the
nerve cells are in contact with the muscle tissue. These joints are named as
neuro - muscular junctions.

148
The structure of a peripheral nerve
A nerve is made up of several nerve fibres. A nerve fibre contains
axons with their coverings called schwann cells. The fibres are grouped into
fasciculi. The number and pattern of fasciculi vary in different nerves. Thus
a nerve trunk possesses many such fasciculi. Such a trunk is surrounded by an
epineuruium. The individual fasciculi are enclosed by a multilayered perineu-
rium. The perineurium surrounds the endoneurium or intra fascicular con-
nective tissue.
In a peripheral nerve the epineurium constitutes 30 -70 % of the total
cross sectional area of the nerve bundle. The thickness is more when there
are more fasciculi. A layer of fat in the epineurium provides a ‘cushion’ effect
to the nerve.
The perineurium contains alternating layers of flattened polygonal cells.
The endoneurium remains condensed around axons. The components of the
endoneurium remain bathed in endoneurial fluid.
The fasciculi of the nerve are supplied blood by vasa nervosum. These
minute blood vessels radiate upto the endoneurium.
Nervous system
The organs of the nervous system are continuous in nature. However,
for study purposes it can be divided into systems and organs.
A. Central nervous system (C N S)
This system includes the brain and the spinal cord or medulla spina-
lis. They are protected by surrounding bones. While the brain is located within
the cranium, the spinal cord is placed within the vertebral canal of the ver-
tebrae. Through an opening called foramen magnum, the spinal cord de-
scends down from the brain.
B. Peripheral nervous system.
It consists of nerves and ganglia. The nerves that are formed from the
brain are called the cranial nerves. There are 12 pairs of cranial nerves and
31 pairs of spinal nerves.
C. Autonomous nervous system.
The nerves in this system transmit impulses from the C N S to smooth
muscles, cardiac muscles and glands. It is also called the involuntary ner-
vous system. It is subdivided into sympathetic and parasympathetic divisions.
149
1. Brain
The brain is safely kept inside the cranial vault. Inside the skull the
brain is surrounded by three protective coverings. They may be grouped un-
der two divisions.
1.Pachymenix -It includes the duramater.
2.Leptomeninges - In includes the arachnoid mater and pia mater.
The duramater is the outermost membrane. It is thick and inelastic in
nature. The arachnoid mater is the middle covering over the brain. In between
arachnoid and piamater there is a space called the subarachnoid space. It
contains cerebro-spinal fluid and blood vessels. The piamater is a delicate
membrane closely applied to the brain. This membrane contains blood capil-
laries supplying blood to the brain cells.

cerebrum

corpus callossum

infundibulum
pituitary gland
cerebellum
pons
medulla oblongata

spinal cord

Fig.3.8.1 L.S. of the human brain

The human brain weighs about 1.3 Kg. It contains more than a billion
neurons. Based on embryological development the brain can be divided as
follows.
1. Prosencephalon (Fore brain) - It consists of the cerebrum and the dien-
cephalon. The cerebrum is the largest part of the brain. It is divided into right
and left hemispheres by a longitudinal fissure. However, at the base the
two hemispheres are connected by a sheet of nerve fibres called the corpus
callossum.

150
 The outer surface of the cerebrum is called the cortex or grey mater.
It is 2 to 4 mm thick. The inner content of the cerebrum is the white mater.
The surface of the cerebrum has several folds called the gyri. They greatly
increase the surface area of the cortex. The shallow grooves in between the
gyri are called the sulci. A central sulcus runs in the lateral surface of the
cerebrum from superior to inferior region.
Each cerebral hemisphere is divided into four lobes. They are the fron-
tal at the front, the parietal towards the top of the head, the temporal on the
side and the occipital at the rear.
The diencephalon contains the thalamus and hypothalamus. This
region is found between the cerebrum and the brain stem.
The thalamus has a cluster of nuclei which act as the relays for par-
ticular sensory pathways. Just beneath the thalamus, the hypothalamus is
present. It contains reflex centres linked to the autonomic system. A funnel
shaped stalk called the infundibulum extends from its floor. It is connected to
the neurohypophysis of the pituitary gland.
2. Mesencephalon (mid brain) - It is the smallest region of the brainstem.
On its dorsal surface there are four rounded bodies called the carpora
quadrigemina.
3. Rhombencephalon (hind brain) - The three main regions of the rhomben-
cephalon are the medulla oblongata, the pons varoli and the
cerebellum.
The cerebellum consists of two hemispheres. Its surface has many
ridges called folia. The cerebellum consists of three parts. They are the small
anterior flocconodular lobe, a narrow central vermis and two large lateral
hemispheres.
The pons is just superior to the medulla oblongata. It contains
ascending and descending nerve tracts.
The medulla oblongata is about 3 cm long. It is continuous with the
spinal cord. It remains as a bridge between the brain and the spinal cord.
Brain stem - The medulla oblongata, pons and mid brain form the brain stem.
It connects the spinal cord to the brain. Ten of the twelve cranial nerves enter
or exit the brain through the brain stem.
Spinal cord - The spinal cord extends from the foramen magnum to the level
of the second lumbar vertebra. It is considerably shorter than the vertebral
151
column. There are two enlargements in the spinal cord. They are the cervical

152
ependymal cells within the lateral ventricles. Remaining 10-12 % is pro-
duced by similar cells in the 3rd and 4th ventricles. These ependymal cells, their
supportive tissue and the associated blood vessels together are called choroid
plexuses. The plexuses are formed by invagination of the vascular piamater
into the ventricles.

3. 9. The Sensory Organs.

Living organism respond to several stimuli such as light, heat, sound,
chemicals, pressure, touch, stretch and orientation. These stimuli are felt by
specific receptors. The receptors convert the stimuli into impulses in the ner-
vous systems.
The touch receptors in the skin are the simplest receptors. Such
receptors are single nerve cells responding directly to the stimulus. Other re-
ceptors are complex sense organs. On these organs the stimulus is chan-
nelled into a receptive region of the organ. Among the several organs, the
most important are the eyes and ears.
The eye
The eye is formed of 3 coats or tunics.
Coats or tunic Regions
1. Outer or fibrous - sclera & cornea
2. middle or vascular - choroid, ciliary body & iris
3. inner or nervous - retina

choroid

ciliary body sclera

cornea
pupil retina
iris

lens
Optic Nerve

Fig.3.9.1. C.S. of human eye

153
 The sclera is the white outer layer of the eye. It covers posterior five-
sixths of the eye. This firm layer provides shape and protects the internal
structures. A small region of the sclera can be seen as the “white of the eye”.
In the front, the outer layer forms a transparent region called the cor-
nea. It permits entry of light. The cornea is made up of a connective tissue
having collagen, elastic fibres and proteoglycans.
The middle tunic of the eyeball is the vascular tunic. It contains most
of the blood vessels. The vascular tunic contains melanin containing pigment
cells. It appears black in colour. A major part of the vascular tunic is found in
association with the sclera and called the choroid. Anteriorly this layer forms
the ciliary body and iris.
The ciliary body consists of smooth muscles called the ciliary
muscles. Contraction of the ciliary muscles can change the shape of the lens.

cornea aqueous humour

pupil lens
iris

ciliary body

Fig.3.9.2. Front of the Eye

The iris is the coloured part of the eye. It may be black, brown or
blue. It is a contractile structure surrounding an opening called the pupil.
Light enters the eye through the pupil. The iris regulates such entry by con-
trolling the size of the pupil.
The inner most tunic of the eye is the retina. It consists of an outer
pigmented retina and an inner sensory retina. The sensory retina is light
sensitive. It contains nearly 120 million photoreceptor cells called rods and
another 7 million cones.

154
Compartments of the eye : The eye has 2 major compartments. There is a
smaller compartment anterior to the lens. Behind the lens there is a larger
compartment.

aqueous humour vitreous humour

Fig.3.9.3. Compartments of the eye

The anterior compartment is divided into two chambers. There is

an anterior chamber found between the cornea and iris. A smaller
posterior chamber lies between the iris and lens. These two chambers are
filled with a substance called the aqueous humor. It helps to maintain
intraocular pressure.
The posterior compartment of the eye is much larger and it
contains a transparent jellylike substance called vitreous humor.
The eye lens is an unique biological structure. It is transparent and
biconvex. It is made up of long columnar epithelial cells called lens fibres.
These fibres have an accumulation of proteins called crystallines. The lens is
placed between the two eye compartments by suspensory ligaments.
The functioning of the eye is aided by accessory structures. They
include the eyebrows, eyelids, conjunctiva and lacrimal apparatus.
The eyebrows prevent the sweat during perspiration from running
down into the eye. They help to shade the eyes from direct sunlight.
The eyelids and associated lashes protect the eyes from foreign ob-
jects. The medial region where the eyelids join has a small reddish-pink mound
called the caruncle. It contains modified sebaceous and sweat glands. There
are two or three rows of hairs attached to the free edges of eyelids. Modified
sweat glands called the ciliary glands open into the follicles of the
eyelashes. It keeps them lubricated. The inner margin of the eyelids contain
Melbomian glands. These glands produce sebum for lubricating the eyelids.
The inner surface of the eyelids and the anterior surfae of the eye are
covered by a thin, transparent mucous membrane called the conjunctiva.
The lacrymal glands or tear glands are situated in the superolateral
corner of the eye orbit. They produce tear at the rate of about 1 ml / day. It

155
helps to moisten the eye surface and wash away foreign substances. At the
corners of the eye there are small openings called the puncta. Each punctum
inturn opens into a lacrymal canaliculus. The lacrimal canaliculi open into a
lacrimal sac. This sac enters into a nasolacrimal duct which opens into the
inferior nasal concha. These ducts help to drain the excess tear. The entire
organization related to ‘tear’ is called the lacrymal apparatus.
Ears (The organs of hearing)
The ears are the organs of hearing and balance. They have three parts,
namely external, middle and inner ears.
External ear - The fleshy part outside the head is called the pinna. It is
made up of elastic cartilage and skin. It is followed by the external auditory
meatus. This passage is lined with hairs and ceruminous glands. These
glands produce cerumen or earwax. The hair and wax prevent foreign ob-
jects from reaching the ear drum. The ear drum or tympanic membrane is
a oval, three layered structure. It separates outer and middle ears.

external auditory meatus

pinna semi circular canals

auditory nerve

cochlea

stapes
incus ear ossicles
tympanic membrane malleus

Fig.3.9.4. Ear - Inner structure

Middle ear - It is an air filled cavity. It contains three auditory ossicles called
the malleus, incus and stapes. The handle of malleus is in contact with the
inner surface of the ear drum. The head of the malleus is attached to the
incus. While the stapes on one side is attached to the incus, its other side fits
into the oval window. The oval window leads to the inner ear.
Inner ear - This region has tunnels and chambers inside the temporal bone
156
called the bony labyrinth. The bony labyrinth contains three regions called
the cochlea, vestibule and semicircular canals. The oval window found in
between the middle and inner ears communicates with the vestibule of the
inner ear. The organs of the inner ear perceive the sound.
3.10 Endocrine system
Our body has two major regulatory systems. They are the nervous
and endocrine systems. Together they regulate and co-ordinate the activi-
ties of all other body structures. The endocrine system sends
information to the tissues it controls in the form of chemical signals. These
signals, in the form of hormones are released into the circulatory system. They
are carried to all parts of the body . Body cells are able to recognise the
chemical signals and respond to them. The hormones of the endocrine glands
regulate and control the functioning of several organs in the body. Thus, this
system in general helps to maintain homeostasis. There are several endocrine
glands in our body. The major glands are the pituitary, thyroid, parathy-
roids, pancreas, adrenals, testes and ovaries.

pituitary

parathyroids thyroid

adrenal
pancreas

ovaries

testes

Fig.3.10.1. The Major Endocrine glands

An understanding of the structure and form of each endocrine gland,

its secretory products and the means by which its activity is regulated is abso-
lutely essential. This knowledge will help us to treat several diseases related
to these glands.

157
Pituitary gland (or) Hypophysis
It is an organ, that secretes eight major hormones. These hormones
regulate numerous body functions and controls the secretory activities of sev-
eral other endocrine glands. The hypothalamus of the brain is connected to
the pituitary. The posterior pituitary is an extension of the hypothalamus.
Structure of the pituitary gland.
This gland is approximately 1 cm in diameter. It weighs 0.5-1g. It is
placed in a region called the sella turcica of the sphenoid bone in the floor of
the skull. It is placed inferior to the hypothalamus. It is connected to it by a
stalk of tissue called the infundibulum.
Based on origin and function the pituitary is divided into two parts.
They are the posterior pituitary or neurohypophysis and anterior pitu-
itary or adenohypophysis.

hypothalamus

infundibulum
pars tuberalis
adenohypophysis
(ant. pituitary)
neurohypophysis pars distalis
(post pituitary)
(a) (b) pars intermedia

Fig.3.10.2. (a) Entire (b) L.S. of the pituitary gland

Posterior pituitary or Neurohypophysis.

The posterior pituitary is continuous with the brain. Hence it is called
the neurohypophysis. During embryonic development, it is formed as an
outgrowth of the inferior part of the brain in the area of the hypothalamus.
The outgrowth of the brain, forms the infundibulum. The distal end of the
infundibulum enlarges to form the posterior pituitary. Since this part of the
pituitary is an extension of the nervous system, its secretions are known as
neurohormones.
Anterior Pituitary or Adenohypophysis
During embryonic development an outpocketing of the roof of the
oral cavity arises. It is called as the Rathke’s pouch. This pouch grows

158
towards the posterior pituitary. Later, the pouch loses its connection with the
oral cavity and becomes the anterior pituitary. The anterior pituitary is subdi-
vided into three areas. They are, the pars tuberalis, pars distalis and pars
intermedia.
Relationship of the pituitary to the brain.
There is a network of blood vessels on the hypothalamus. It is called
the primary capillar y nerwork. A portal system called the
hypothalamohypophyseal portal system extends from a part of the hypo-
thalamus to the anterior pituitary (a portal blood vessel begins and ends as
capillaries). The portal system in turn opens into the secondary capillary net-
work of the anterior pituitary. The neurohormones produced by the hypothala-
mus are collected by the primary capillary network. Through the portal sys-
tem they enter into the secondary network of the anterior pituitary.
Thyroid gland
The thyroid gland is composed of two lobes. They are placed on the
lateral sides of the upper portion of the trachea. These lobes are connected by
a narrow band of thyroid tissue called the isthmus. The isthmus extends across
the anterior aspect of the trachea.

trachea

thyroid glandular cells

acinus
parathyroid

Fig.3.10.4. Thyroid C.S

Fig.3.10.3. Thyroid and Parathyroid glands

The thyroid is one of the largest endocrine glands. It weighs approxi-

mately 20g. It is richly supplied with blood capillaries. It is more red than its
neighbouring tissues.
The gland is composed of numerous follicles. They are small spheres.
Their walls are made up of cuboidal epithelial cells. The central cavity or
lumen of each follicle is filled with a protein called the thyroglobulin. It stores
large amount of thyroid hormone. The thyroid secretes thyroxine and calci-
tonin.
159
Parathyroid glands.
The parathyroid glands are found in association with the thyroid glands.
They are found embedded in the posterior part of each lobe of the thyroid
gland. There are four parathyroid glands. Inside the glands the cells are
organised in densely packed masses. The cells of the glands secrete parathy-
roid hormone.
Adrenal glands or Suprarenal glands.
These glands are found near the superior pole of each kidney. They
are surrounded by adipose tissue. The glands are enclosed by a connective
tissue capsule.
The adrenal glands are composed of an inner medulla and outer cor-
tex. These regions are formed from two separate embryonic tissues. The
medulla consists of closely packed polyhedral cells. They are centrally lo-
cated in the gland. The cortex is composed of smaller cells. These cells form
three distinct layers, namely the zona glomerulosa, the zona fasciculata
and the zona reticularis. These layers are structurally and functionally spe-
cialized.
The adrenal medulla secretes two major hormones. They are epi-
nephrine (or adrenaline) and norepinephrine (or noradrenaline). The hormones
of the adrenal cortex are the cortisol and aldosterone.
Pancreas.
The pancreas lies between the greater curvature of the stomach and
the duodenum. It is an enlarged structure. It is approximately 15 cm long. It
weighs 85 -100g.
The pancreas is both an exocrine and an endocrine gland. The endo-
crine part consists of pancreatic islets (islets of Langerhans). They are
approximalety 500,000 to 1,000,000 in number. The islets are distributed in the
pancreas. The islets are composed of alpha (α) cells (20%) and beta (β )cells
(75%). While the œ cells secrete glucagon the β cells secrete insulin. A
third type of cells called the delta ( δ ) cells (5%) have been identified. These
cells secrete somatostatin.

3.11 Urinary system

It is customary to link the organs of urinary excretion and reproduc-
tion as urino-genital system. The suitability of this concept is questionable.
160
The urinary and reproductive organs differ in their embryological origin and
development. In postnatal human beings, the association between the compo-
nents of the urinary and the reproductive systems is very much limited. Hence
the urinary and reproductive systems are considered separately.
The urinary organs comprise, two kidneys (renes), ureters, the uri-
nary bladder (vesica urinaria) and the urethra.
renal vein
renal artery
kidney

ureter

urinary bladder

urethra
Fig.3.11.1. Human Urinary system
The kidneys.
The kidneys are bean shaped organs. In fresh state the kidneys are
reddish brown in colour. They lie on the posterior abdominal wall. In the
abdomen, the right kidney is slightly lower than the left. It is because of the
presence of liver superior to it. The kidneys are surrounded by adipose tissue.
Each kidney is about 11 cm in length, 6cm in breadth and 3cm in antero-
posterior dimensions. In adult males the average weight of kidney is about
150g (in adult female 135g).
cortex
renal hilum

renal pyramids renal artery

renel vein
renal pelvis

calyx
medulla
ureter

Fig.3.11.2. L.S. of Kidney

161
 The inner margin of each kidney has a small depression called the
hilum. The renal artery and nerves enter and the renal vein and the ureter
exit at this region. The hilum opens into a cavity called the renal sinus.
Each kidney is enclosed by a fibrous connective tissue layer, called
the renal capsule. Internally the kidney is divided into an outer cortex and an
inner medulla. The medulla consists of several cone-shaped
renal pyramids. Extensions of the pyramids called the medullary rays, project
from the pyramids into the cortex. Extension of the cortex called renal col-
umns, project between the pyramids. The tips of the pyramids are called the
renal papillae. They are pointed toward the renal sinus. The renal papillae
are surrounded by funnel shaped structures called the minor calyces. The
minor calyces of several pyramids join together to form larger funnels called
major calyces. There are 8-20 minor calyces and 2 or 3 major calyces per
kidney. The major calyces converge to form an enlarged channel called the
renal pelvis. The renal pelvis then narrows to form the ureter. The ureter
leaves the kidney and gets connected to the urinary bladder.
Nephron.
The basic functional unit of each kidney is the nephron. There are
approximately 1.3 million nephrons in each kidney. Atleast 450,000 of them
must remain functional to ensure survival. Each nephron consists of an en-
larged terminal end called the renal corpuscle, a proximal tubule, a loop
of Henle and a distal tubule. The distal tubule opens into a collecting duct.
The renal corpuscle, proximal tubule and distal tubules are in the renal cortex.
The collecting tubules and parts of the loops of Henle enter the renal medulla.
efferent blood vessels

uriniferous
afferent blood tubule
vessels

Bowman’s capsule

glomerulus

proximal tubule
distal tubule
collecting tubule

loop of Henle

Malpighian capsule Fig.3.11.3. Nephron

162
 Most nephrons measure 50-55 mm in length. 15% of the nephrons
are larger and they remain near the medulla. These are called the
juxtamedullary nephrons. They have larger loops of Henle.
The renal corpuscle of the nephron consists of a Bowman’s capsule
and a bunch of capillaries called the glomerulus.
In the Bowman’s capsule the outer and inner layers are called pari-
etal and visceral layers respectively. The outer parietal layer is composed of
simple squamous epithelium. The inner visceral layer surrounds the glomeru-
lus. It consists of specialized cells called podocytes. The walls of the glom-
erular capillaries are lined with endothelial cells. There is a basement
membrane between the endothelial cells of the glomerular capillaries and the
podocytes of Bowman’s capsule. The capillary endothelium, the basement
membrane and the podocytes of Bowman’s capsule make up the filtration
membrane.
The glomerulus is supplied with blood by an afferent arteriole. It is
drained by an efferent arteriole.
The cavity of Bowman’s capsule opens into the proximal tubule. The
proximal tubule is also called the proximal convoluted tubule. It is approxi-
mately 14mm long and 60 µm in diameter.
Posteriorly the proximal tubule continues as the loop of Henle. Each
loop has a descending limb and an ascending limb. The first part of the de-
scending limb is similar in structure to the proximal tubule. The loops of Henle
that extend into the medulla become very thin near the end of the loop. The
first part of the ascending limb is also very thin and it consists of simple squa-
mous epithelium, but it soon becoms thick. The distal tubules, also called the
distal convoluted tubules are not as long as the proximal tubules.
Ureters and Urinary bladder
The ureters extend inferiorly from the renal pelvis. They arise medi-
ally at the renal hilum to reach the urinary bladder. The bladder is meant for
temporarily storing the urine. The urinary bladder is a hollow muscular bag. It
lies in the pelvic cavity. The size of the bladder depends on the presence or
absence of urine. The bladder capacity varies from 120-320ml. Filling upto
500 ml is tolerated. Micturition will occur at 280ml. The ureters enter the
bladder inferiorly on its posterolateral surface. The urethra exits the bladder
inferiorly and anteriorly. At the junction of the urethra with the urinary bladder

163
smooth muscles of the bladder form the internal urinary sphincter. Around
the urethra there is another external urinary sphincter. The sphincters control
the flow of urine through the urethra.
In the male the urethra extends to the end of the penis where it opens
to the outside. In male the urethra is 18-20cm long. In the female the urethra
is shorter. It is about 4 cm long and 6 mm in diameter.
3.12. Reproductive system
The process of sexual reproduction is a wonderful act in nature. This
process, apart from ensuring a healthy progeny provides an oppurtunity to
produce enormous range of genetically varied offsprings. Organisms have
adopted several strategies for sexual reproductive processes. Such
adaptations have resulted in suitable morphological, anatomical and behav-
ioral modifications. Human reproductive organs as internal and external geni-
talia are highly sophisticated yet simple in their functioning. The functioning is
in accordance with psychological and endocrinological thresholds. An
academic approach towards an understanding of the human male and
female reproductive organs and their functions will go a long way in
avoidance of unethical, unhealthy and unhygenic practices encoun-
tered at specific periods in life.
Male reproductive organs
The male reproductive system consists of the testes (singular : tes-
tis), epididymides (sing: epididymis), ductus deferentia or vasa deferentia
(sing : ductus deferens, vas deferens), urethra, seminal vesicles, prostate
gland, bulbourethral glands, scrotum and penis.

ureter

urinary bladder
prostate gland
vas deferens
urethra
epididymis seminal vesicle

penis anus
testis
scrotum
Fig. 3.12.1. Human male reproductive organs
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Testes : The testes are the primary reproductive organs or gonads in the
male. These are suspended in the scrotum by scrotal tissues.
The sperm cells are temperature sensitive. They do not develop nor-
mally at usual body temperatures. Hence the testes and epididymides in which
the sperm cells develop, are located outside body cavity in the scrotum, where
the temperature is low.
The left testis usually is 1 cm lower than the right. An average testis
is 4-5 cm in length, 2-5cm in breadth. Its weight varies from 10.5-14g.
The outer part of each testis is a thick, white capsule called tunica
albuginea. Internally the testis contains several incomplete septa. The septa
divide each testis into about 300-400 cone shaped lobules. The lobules contain
seminiferous tubules and interstitial cells or Leydig cells. Sperm cells de-
velop within the seminiferous tubules.

epididymis

coiled seminiferous tubule

tunica albuginea

vas deferens
testis

Fig. 3.12.2. L. S. of the Testis

The seminiferous tubules are extensive. The combined length of the

tubules in both testes is nearly 800 metres. These tubules through a set of
short, straight tubules open into tubular network called the rete
testis. The rete testis in turn open into efferent ductules. Internally the tu-
bules and ductules are lined by ciliated columnar epithelium. These cells help
to move the sperm cells out of the testis.
Epididymis : It is formed of extremely convoluted ductules coming out of the
testis. It occurs on the posterior side of the testis. The maturation of sperm
cells occurs within the ductules of the epididymis.

165
Vas deferens or ductus deferens : It emerges from the tail end of the
epididymis and ascends along the posterior side of the testis. It becomes asso-
ciated with the blood vessels and nerves that supply the testis. Collectively
these structures constitute the spermatic cord. Thus the spermatic cord con-
sists of (1) Vas deferens (2) testicular artery and venus plexus (3) lymph
vessels (4) nerves (5) fibrous processes and muscles. This cord enters into
the pelvic region. The end of the vas deferns enlarges to form the ampulla. At
this region the vas deferens is surrounded by smooth muscles capable of peri-
staltic contraction. They help to propel the sperm cells through the ductus
deferens.
Ejaculatory duct : Nearer to the ampulla of each vas deferens there is a sac
like seminal vesicle. It joins the ductus deferens to form the ejaculatory
duct. These ducts are about 2.5 cm long. They project into the prostate gland
and end by opening into the urethra.
Urethra : The male urethra extends from the urinary bladder to the distal end
of the penis. It is about 20 cm long. It is a passageway for both urine and
reproductive fluids. The urethra is divided into three parts. They are
1. The prostatic Urethra - It is closest to the bladder and passes through the
prostate gland.
2. The membranous urethra - It is the shortest part of the urethra and it
extends from the prostatic urethra.
3. The spongy urethra or penile urethra - It is the longest part of the
urethra. It extends from the membranous urethra, through the length of the
penis. There are several minute mucus secreting urethral glands opening into
the urethral passage.
Penis - It is the male copulatory organ. It consists of two parts namely the
radix or root and the corpus or body. The radix attaches the penis to the
lower abdomen. The corpus is normally pendulous. It is covered by a loose
skin.

corpus cavernosum

spongy urethra corpus spongiosum

Fig. 3.12.3. C. S of Penis

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 The corpus of the penis consists of three masses of erectile tissue.
Flooding these tissues with blood causes the penis to enlarge and become
firm. These tissues are the right and left corpora cavernosa and the median
corpus spongiosum penis. Most of the corpus is formed of the corpora
cavernoas. The corpus sporgiosum penis surrounds the urethra and near the
end of the penis it expands into a conical, glans penis. Its
swollen base is the corona glandis.
The skin over the penis is thin. It is loosely connected to the tunica
albuginea. At the tip of the penis it is folded to form the prepuce or the
foreskin. It overlaps the glans penis. The corona glandis and penile neck
have numerous preputial glands.
Seminal vesicles - These are two sac-like structures located between the
bladder and rectum. Each vesicle is about 5 cm long. Their secretions contrib-
ute about 70% of the seminal fluid.
Prostate - It is a firm structure. It is partly glandular and partly fibromuscu-
lar. It is found around the beginning of the male urethra. It is about 3 cm in
diameter. It weighs about 8g.
The muscular part of the prostate may help in dilating the urethra to
hold the seminal fluid (3-5ml) during the period of sexual excitement prior to
ejaculation.
After the middle age the prostate often enlarges. It may project into
the bladder and interrupt urination.
Bulbo-urethral gland - These are two glands. They are small round masses
about 1 cm in diameter. They lie lateral to the membranous urethra. Its secre-
tion may control genito-urinary diseases.
Scrotum - It is a fibromuscular sac. It contains the testes and their associated
ducts. It is divided into right and left by cutaneous raphe. Its left side is usually
lower. The external appearence varies according to age and body tempera-
ture. The scrotal skin is thin and pigmented. It has numerous sweat glands and
nerve endings.
Female reproductive organs
In human female the internal reproductive organs are the ovaries,
uterus, uterine tubes and vagina. Externally the organs are the mons pu-
bis, labia majora and labia minora, clitoris and vestibular glands.

167
Ovaries - These are paired structures. The two ovaries are placed on each
side of the uterus in the pelvic region. They are greyish pink in colour. Each
ovary is almond shaped. They are about 3cm long,1.5cm wide and 1cm thick.

ureter
fallopian tube or
uterine tube ovary
uterus

urinary bladder cervix

pubic bone rectum
urethra
anus

Fig. 3.12.4. Human female reproductive organs

The ovary is attached to the posterior surface of the inner body wall
by a membranous fold called the mesovarium. The ovary is further supported
by suspensory and ovarian ligaments.
Ovarian structure - In young female the surface of the ovary is covered by
a layer of ovarian surface epithelium. It consists of a single layer of cuboi-
dal cells. Beneath the epithelium the ovary is surrounded by a tough coat
named tunica albuginea. It is made of collagenous tissue.
secondary follicle
primary follicles
cortex

mesovarium granulosa cells

medulla

tunica albuginea theca interna

cumulus mass
corpus luteum
Fig. 3.12.5. Histology of the Ovary

The overy proper is divisible into two regions, namely the cortex and
the medulla. The cortex region contains the ovarian follicles. The medulla is
interior. It receives blood vessels and nerves at the hilum.
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 After puberty the cortex forms the major part of the ovary. It con-
tains ovarian follicles and corpora lutea of various sizes. Their size de-
pends on the stage of menstrual cycle or age. The cortex is filled with stroma
composed of collagen. The follicles are embedded in the stroma.
Ovarian follicles
The formation of the female gamete has many different phases and it
is complex. At birth, the primordial follicles are found in the superficial zone of
the cortex. They contain primary oocytes (about 25mm in
diameter). Each one of them is surrounded by a single layer of flat follicular
cells. The follicles undergo changes as the female attains puberty. The vari-
ous follicular stages are :
1. Primary follicle - The follicle cells are converted from squamous to cuboidal
cells. The follicular membrane or membrana granulosa becomes multilay-
ered. The oocyte increases in size. It has an outer thick layer called the zona
pellucida. The follicular cells divide and form granulosa cells.
2.Secondary follicle - It is about 20µm thick. The granulosa cells surround
the oocyte and form a mound of cells called the cumulus ovaricus. The inner
and outer theca become prominent. The theca interna is well established.
3. Tertiary follicle - Only one follicle reaches the tertiary stage. It increases
in size (2mm diameter). Now it is called the graffian follicle. The oocyte and
ring of cells surrounding the oocyte (corona radiata) break away and float
freely in the follicular fluid. Finally the wall of the follicle ruptures and the
contents are released into the peritoneum.
The ovary of the foetus at 5 months gestation has 7 million oocytes.
At birth the ovary of the child contains about 1 million oocytes. Due to further
degeneration at the time of puberty only about 40,000 oocytes remain. Of the
40,000 oocytes only about 400 undergo ovulation during the reproductive years.
Corpus luteum - It is formed after ovulation. The walls of the empty follicle
collapses and fold extensively. The granulosa cells of the theca externa get
enlarged.
They are now termed as luteal cells. They secrete hormones. In
pregnancy the corpus luteum persists. Otherwise, it degenerates after 10-12
days. The connective tissue cells get enlarged. It becomes white in colour and
is now called as the corpus albicans. In course of time it shrinks and
disappears.

169
Uterine tubes (Fallopian tubes) - There are two uterine tubes or oviducts,
one on each side of the uterus. Each one is associated with a ovary. Each
tube is about 10 cm length. The terminal part of the tube is enlarged to form
the infundibulum. It opens into the peritoneal cavity. The opening is called the
ostium. The uterine tube consists of three parts. The part nearer to the in-
fundibulum is called the ampulla. It is the longest part. That part of the tube
nearer to the uterus is called the isthmus. It is narrow. The tubular part enter-
ing into the uterus is called the uterine or intramural part.
fundus
isthmus uterine part
ovary
endometrium
myometrium
Uterus perimetrium
cervix cervical canal
ostium

vagina

Fig. 3.12.6. Human female reproductive system

Uterus
It is a hollow thick walled muscular organ. It is pear shaped. It is
about 7.5cm long and 5 cm wide. It weighs about 50g.
During pregnancy its weight may go upto 1kg. Its larger rounded part
is called as the fundus. The narrower part is called as the cervix. The cervix
is directed inferiorly. The middle part is the body . The uterus
continues as the cervical canal and opens into the vagina through a opening
called the ostium.
The wall of the uterus is three layered. The outermost layer is the
perimetrium or serous layer. The major part of the wall is made up of the
next layer called the myometrium or muscular coat. The
innermost layer is the endometrium or mucous membrane. The endometrium
is a functional layer. It undergoes menstrual changes and sloughing during
female sex cycle.
Vagina - It is the female copulatory organ. It is a fibromuscular tube. It is
about 10 cm long. It extends from the uterus to the outside. The vaginal pas-
sage is used during intercourse and it allows menstrual flow and child birth.
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External Genitalia
Vestibule - The external female genitalia is known as the vulva or puden-
dum. It consists of the vestibule and its surrounding structures. The vestibular
region remains in between the two labia majora. It contains the vaginal open-
ing and the urethral opening. The vestibular region is surrounded by the
mons pubis anteriorly and labia majora and labia minora on the lateral
sides.
Mons pubis - It is a rounded eminence situated anteriorly. It is made up of
subcutaneous adipose connective tissue. It is covered by coarse hair at the
time of puberty. It corresponds to similar structure in the male.
Labia majora - These are two longitudinal folds of skin. They form the outer
boundary for the vestibule.
Labia minora - These two small skinfolds lie between the labia majora. They
remain nearer to the vaginal opening.
Clitoris - It is homologus with male penis. It is an erectile structure. It is
found in the anterior margin of the vestibule. It is a sensitive region having
sensory receptors.
Hymen vaginae - It is a thin mucous membrane. It is found within the vagi-
nal orifice or opening. If the membrane completely closes the vaginal opening,
it should be removed to allow menstrual flow. In young women the hymen
may normally get torn during physical exercise. In some women it may be
absent. It has no established function.
External urethral opening - This opening is about 2.5 cm below the clitoris.
It is anterior to the vaginal opening. It remains as a small cleft.

171
 Self evaluation
Choose the correct answer
1. The cornified region of the skin is formed of
a) stratum lucidum b) stratum basale
c) stratum spinosum d) stratum corneum
2. The goose flesh is formed due to the contraction of
a) diaphragm b) errector pili
c) trapezius muscle d) gluteus maximus
3. The skin colour is due to the pigment.
a) melanin b)haemoglobin
c) neutral red d) Janus green
4. The number of facial bones are
a) 26 b) 25
c) 14 d) 22
5. The cervical vertebra supporting the head is
a) axis b) atlas
c) sacral d) lumbar
6. Choose the flat bone in our body.
a) skull bone b)ribs
c) sternum d) all the above
7. The number of thoracic bones are
a) 5 b)12
c) 7 d) 1
8. The bone that holds the upper limb away from the body is
a) scapula b)pelvic bone
c) clavicle d) femur

172
9. The broadest muscles are named as
a) deltoid b) gracilis
c) longus d) lattismus
10. In shape the deltoid muscle is a
a) square b) slender
c) circular d) triangular
11. The major breathing movement is due to
a) scalene b) thoracic
c) diaphragm d) intercostals
12. The largest salivary glands are
a) parotid b)submandibular glands
c) sublingual glands d) labial glands
13. The human dentition is
a) heterodont b) thecodont
c) diphyodont d) all the above
14. The length of the duodenum in human alimentary canal is
a) 8 cm b) 1.8 m
c) 9 cm d) 25 cm
15. The lung is surrounded by
a) duramater b) pericardial membrane
c) pleura d) meninges
16. Breathing process can be interfered with due to
a) closure of the ileo-colic valve b) enlargement of the tonsil
c) closure of pyloric sphinctes d) vibration of the vocal cord
17. The reduction in blood pressure may be caused due to
a) distributing vessels b) resistance vessel
c) exchange vessels d) reservoir vessels
173
18. Vaso-dilation and vaso-constriction are caused by
a) tunica intima b) exchange vessels
c) tunica media d) tunica adventitia
19. The wall of the blood vessels are supplied with blood by
a) vasa nervosum b) exchange vessels
c) vasa vasorum d) capacitance vessels
20. The exchange vessels are
a) arteries b) arterioles
c) Venules d) Capillaries
21. Spleen is located on the left side of
a) the abdominal cavity b) the thoracic cavity
c) the lung d) the kidney
22. The synapses are formed between
a) nerves and muscles b) nerve tissues
c) capillaries d) organs
23. The cerebral hemispheres are connected by a sheet of nerve fibres called
a) corpora quadrigemina b) choroid plexus
c) corpus callossum d) cauda equina
24. The number of human cranial nerves is
a) 12 pairs b) 31 pairs
c) 10 pairs d) 11 pairs
25. The Melbomian glands produce
a) sebum b) tear
c) wax d) oil
26. The interoccular pressure is maintained by
a) aqueous humor b) vitreous humor
c) cerebro spinal fluid d) lymph fluid
174
27. The hypophysis is connected with the brain through
a) pars tuberalis b) adeno hypophysis
c) hypothalamus d) pars distalis
28. The average weight of human thyroid gland is
a) 10 gms b) 20 gms
c) 500 gms d) 20 kg
29. The average weight of kidney in adult female is
a) 150 g b) 135 g
c) 75 g d) 250 g
30. The bunch of capillaries in the Bowman’s capsule forms the
a) medullary rays b) calyces
c) glomerulus d) capillary endothelium
31. The interstitial cells are otherwise called
a) Leydig cells b) Sperm cells
c) Glandular cells d) Secretory cells
32. The ovary of the foetus at 5 months gestation has
a) 40,000 Oocytes b) 7 million Oocytes
c) 400 Oocytes d) No Oocytes
33. The inner layer of membrane lining the uterus is
a) perimetrium b) myometrium
c) endo metrium d) serous layer
34. The uterine tubes are otherwise called as
a) ureters b) spermiducts
c) fallopian tubes d) birth canal

175
 Part - II
1. What is keratinization ?
2. What is callus ?
3. What are floating ribs ?
4. What is a synovial joint ?
5. Name the two catagories of bones.
6. What is foramen magnum ?
7. What is acetabulm ?
8.Differentiate skeletal and visceral muscles.
9. Name the kissing muscles
10. Write a short note on the structure of the cardiac muscle.
11. Name the muscles which are essential for the movement of the neck.
12. Provide the human dental formula
13. What is gingiva.
14.Name the three pairs of Salivary glands.
15. Name the four parts of the Colon.
16. What is Adam’s apple ?
17. What is carina ?
18. What is acinus ?
19. What is double circulation ?
20. Name the layers found in the wall of the heart.
21. Provide the root of systemic circulation
22. What is the role of B-lymphocytes ?
23. What are sulci and gyri ?
24. What is a neuromuscular junction ?
25. What is choroid plexuses ?
176
26. What is melbomian gland ?
27. What is Rathke’s pouch ?
28. What are podocytes ?
29. What is the function of the ciliary muscles ?
30. What is an eardrum ?
31. Name the parts of the anterior pituitary.
32. Name the layers of the adrenal cortex.
33. What is the role of prostate glands ?
34. What is corpus luteum ?
35. What is graffian follicle ?
Part - III
1. Draw the different layers of the skin and label the parts.
2. Give an account of the nail and its structure
3. Describe the structure of typical human vertebra
4. Describe the structure of a typical long bone.
5. Describe the various types of joints.
6. Give an account of the muscles of the lower limb
7. Draw a neat labelled sketch of a tooth.
8. Give a description of the human liver
9. Describe the structure of stomach with diagram.
10. Explain the structure of the larynx with diagram.
11. Describe the paired and unpaired cartitages of larynx
12. Write notes on portal circulation
13. Describe the types of the blood vessels.
14. Draw a neat labelled sketch showing the internal structure of the heart
15. Give an account of the thymus
16. Explain a) Lymph nodes
b) Tonsils

177
17. Describe the structure of a Neuron with diagram.
18. Explain the cross section of spinal cord with diagram
19. What is the structure of a peripheral nerve ?
20. Explain the organization of the lacrimal apparatus in human eye
21. Draw a neat labelled sketch of the C.S. of human eye.
22. Explain the structure of the inner ear.
23. Describe the structure of the thyroid gland with diagram.
24. Describe the endocrine nature of the pancreas
25. Provide the structure of human kidney
26. Explain the various stages of the Ovarian follicles.
27. Describe the Ovarian structure with diagram.
28. Give an account of corpus luteum
Part - IV
1. Explain the structure of the various skin-dervatives with suitable diagrams.
2. Name bones in the skull of man. Explain the same with a neat diagram.
3. Write an essay on the structure and organization of the axial skeleton in
human beings.
4. Explain the appendicular skeleton with diagram.
5. Name the muscles of the upper limb and explain how they work.
6. Give an account of the organs of digestion in the buccal cavity.
7. Describe the structure of digestive system with diagram.
8. Explain the structure of respiratory system with diagram.
9. Write an essay on structure and types of blood vessels
10. Describe the systemic and pulmonary blood circulations in man with
diagram.
11. Explain the structure of human heart.
12. Provide a detailed description of the anatomy of human brain
13. Explain the structure of human urinary system with diagram.

178
14. Describe the structure of a nephron with diagram.
15. Give an account of the structural organization of the hypophysis
16. Write an essay on the primary sex organs and associated structures of a
human male.
17. Explain the structure of female reproductive organs in human with suitable
diagrams.
18. Name the muscles in the human trunk region and explain how they work.
Label the diagrams

179