Course Tutor: Mr.

Sadiq Rabiu Umar

Department of Anatomy, General Sciences Unit

Course: Anatomy/Physiology (100 level) Students

Lecture 1
INTRODUCTION
An adequate basic knowledge of the body structure, including their position and in normal health
will certainly enable such individual to understand the abnormal state of health and then takes
appropriate measures to maintain and promote health status.

The human body develops from a single cell called the zygote, which results from the fusion of
the ovum (female egg cell) and the spermatozoon (male germ cell).

Human Anatomy:
The word anatomy is a latin word which refers or means to dissect or cut for the purpose of study
of the structure of the human body and the relationship between the body parts.

It is the science that deals with the structure of body including their arrangement and relationship
to one another, and the microscopic aspect of each structure. The following are taken into
consideration during the study of structures:

LOCATION Place where the structure is situated

MEASUREMENT Size of the structure

EXTENT Area covered by structure

RELATIONS Association between two or more structures

ORIGIN Where the structure is derived from

COMPOSITION What the structure is made up of

Body structure include: Brain, Skin, Muscles etc. each of these structures are highly organized in
the human body.

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Anatomy is been classified into the followings
 Macroscopic anatomy- otherwise known as Gross anatomy is the scientific study
of the various structures of the body as seen by naked eyes. The gross anatomy
includes the following:
 Regional /Topographic anatomy- this studies the body region by region e.g.
upper limbs, lower limbs, thorax, abdomen pelvis, head and neck.
 Microscopic anatomy: this deals with the study of structures that cannot be seen
with naked eye or microscopic study of the structure of tissues.

 Developmental anatomy: study of development from fertilization up to full

matured individual.
 Surface anatomy: this is the study of the form (morphology) and markings of the
surface of the body.

Human Physiology:
Is the study of function of body parts and (how the parts of the body work, and the ways in
which they cooperate together to maintain life and health of the individual). Body functions
include metabolism (synthesis and breaking down) or cellular activities growth and development,
movement and posture, gaseous exchange.

BRANCHES OF HUMAN PHYSIOLOGY

 Nutritional physiology: this deals with food nutrients (balanced diet) and how they
affect health, growth and structural development.
 Blood physiology or Haematology: this deals with the study of blood, its composition
and disease conditions affecting the body.
 Human medicine: this deal with the study of health practice diagnosis and curative
procedures that lead to good and sound health.
 Hygiene: this is also called physiology of cleanliness. It also includes personal and
environmental health and cleanliness.

IMPORTANT OF HUMAN ANATOMY AND PHYSIOLOGY

1. AS A BASIC SCIENCE:
Human anatomy and physiology is a universal accepted preliminary introduction into all
curricular guiding all schools and colleges, institutions offering both health and basic
medical courses whether curative or preventive in the country. It is called basic sciences
because it is the foundation of health and medical practice.

2. PROMOTION OF PERSONAL HYGIENE:

It’s also promotes the principal ethics of good hygiene. Every student learns the effects of
disease causing organisms on the human body and how to keep the human free from
infections.

3. PREVENTIVE CARE APPROACH:

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 The most important principle of anatomy and physiology is the preventive approach to
health through physical education using body exercise, massages, and physical fitness
process internal or cellular balances, regulation of body fluids, electrolytes, and stress
reduction.

4. CURATIVE CARE APPROACH:

It emphasizes simple first aid treatment such as drug administration, history of disease
and infections and curative procedures for healing and total well-being.

5. FOR RESEARCH PURPOSES:

Human anatomy and physiology are research tools in modern health or medical practice.
It studies the development of the human fetus from a fertilized egg or zygote microscopic
examination of tissues, prevention and storage of laboratory specimen and radiographic
techniques used in health practice.

6. AS A FORENSIC TECHNOLOGY:
It’s also used in security department for crime control and detection. This involves use of
finger prints, anatomical physiognomy (features of a person’s face) genetic scrunity and
foot prints. Also body odours, skin colour, height, weight, could be used as parameters of
identification for crime detection and control.

7. AS A COURSE OF STUDY:
Human anatomy and physiology is also awarded on certificate degree qualification.
Students could enroll into higher institution to undertake these sciences as professional
career after which they are expected to teach to teach or work as health instructors in
health care centers.

8. AS A SURGICAL GUIDE:
In hospitals and clinics, human anatomy and physiology serve as guides to doctors and
theatre nurses, even the community health workers involved in wound dressing and
injection administration.

Basic features of surface anatomy and physiology are very necessary such as skin creases
or surgical lines, pigmented body lines, body grooves and fossae of curves. These guides
or features enables the health worker to treat injuries wound, fracture and tears along the
human body.

9. IN DIAGNOSIS:
A good knowledge of human anatomy and physiology helps health worker to
systemically diagnose an individual (patient) using simple changes in the structural
appearances of the human body such as color of the eyes, dryness of the tongue,
temperature of the skin, appearance of the lips, and color of the skin.

Lecture 2

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ANATOMICAL TERMINOLOGIES
These are the terms used in all anatomical texts and charts to describe any region or part of the
body. Anatomical terminologies make directional terms clear, such that any part of the body
could be related to others.

Term of position
This is the term used when the human body is in the standing or upright position facing forward
with two arms by the sites of the body, the palms of the hands facing forward, while the two feet
are place together, and facial expression is neutral. Once the body is in anatomical position, it is
easy to visualize and understand how it is organized into various regions. And these are:

ANATOMICAL TERM DEFINATION EXAMPLE

Lateral By the side The index finger is lateral to the

middle finger
Superior Above The heart is superior to the liver

Medial Close to midline The ulna bone is on the medial side of

the forearm
Inferior Below the liver is inferior to the heart

Anterior/Ventral In front The sternum is anterior to the heart

Posterior/Dorsal In the back The heart is posterior to the sternum

Proximal Nearer to The humerus is proximal to the radius

Distal Away from The radius is distal to the humerus

Superficial On the surface of the The skin is superficial to the muscles

body

Deep Away from the surface of The muscles are deep to the skin
the body

Anatomical terms of movement

All movements of the body take place at joints and these include the followings:

Flexion Reducing angle of a joint

Extension Indicates straightening or increasing the angle between

the bones or parts of the body.

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 Abduction Means moving away from the median plane

Adduction Means moving toward it

Circumduction Is a circular movement that involves sequential flexion,

abduction, extension, and adduction

Medial rotation Rotation toward midline

Lateral rotation Rotation toward lateral direction

Anatomical planes

The three (3) major group of planes pass through the body in the anatomical position.

 Coronal plane: Are oriented vertically and divides body into anterior and posterior parts
 Saggital plane: Are also oriented vertically and divided the body into right and left
parts.
 Transverse/horizontal/axial plane: This divides the body into superior and inferior
parts.

HUMAN BODY STRUCTURAL LEVELS OF ORGANIZATIONS

The structural levels of organization determine the levels of development in the human body,
specifically during their growth during pregnancy.
- The human body is organized from the lowest form of development, which is marked by
conception, to the highest which is characterized by the body’s completed basic
development just before birth.
- Chemical level:
When it comes to the human body, it doesn’t get any smaller than the chemical
level. This is the level reserved for the building blocks of human life. Including

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 atoms and molecules, which combine to make organelles, which determine cell
function. These functions can include cell membranes, mitochondria and
ribosomes.

- Cellular level:
The cells of human body are the functional unit of life. When a human life begins,
it starts as a single cell and grows as those cells multiply through mitosis, which
makes sure the cellular structure established by the single cell is replicated over
and over again and that the body gets a full 46 chromosomes.

- Tissue level:
This is when similar types of cell come together to form tissue in the body. There
are four (4) distinct types of tissue in the body. Epithelial tissue it covers the skin
and internal lining of body organs. Connective tissue includes blood, cartilage and
bone. Muscular tissue produces force, causes motion and gives the body
definition. Nervous tissue allows electrical impulses to travel throughout the
human body.

- Organ level:
When tissues of a similar type come together during the body’s development, they
form organs. Most organs contain all four types of tissues mentioned above.
Organs usually form to perform specific function, which can include everything
from blood movement (heart) to waste management (the liver and kidneys) to
reproduction (male and female sex organs).

- System level:
This is the highest level of the levels of structural organization in the human body.
All of the previous building blocks come together to form systems that perform
specific human function. These organ systems include the cardiovascular system,
skeletal system, gastrointestinal system, etc. In all the human body has eleven
(11) body system.

CELL
Are the smallest independent units of living matter and there are millions in the body. They are
too small to be seen with the naked eye, but when magnified using a microscope different types
can be distinguished by their size, shape and the dyes they absorb when stained in the laboratory.
Each cell type has become specialized and carries out a particular function that contributes to
body needs. It is the structural and functional unit of life which perform a particular function that
maintain the homeostasis and contribute to the health of an individual.
The cell was discovered by Robert Hooke in 1665. The cell theory first developed in 1839 by
Mattias Jakob Schleiden and Theodor Schwann, states:

1. Cells are the smallest units and functional of life

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2. All living organisms are made up of cells
3. All cells come from pre-existing cells these are all the theories
4. All cells contain the hereditary information to the generation of cells.

CELL ORGANELLES
Organelles means “small organs” are part of the cell which are specialized to carry out one or
more vital functions, analogous to the organs of human body (such as heart, liver, lungs, kidneys,
with each organ performing a different function).
These includes: Nucleus, Mitochondria, Ribosome, Golgi apparatus, Lysosome, Endoplasmic
reticulum, and Cytoskeleton etc.

Cell membrane
The cell membranes, or plasma membrane, surround the cytoplasm of a cell. In animals, the
plasma membrane is the outer boundary of the cell, while in plant and prokaryotes it is usually
covered by cell wall.
This membrane serves to separate and protect a cell from its surrounding environment and is
made mostly from a double layer of phospholipids, which are amphiphilic (partly hydrophobic
and partly hydrophilic).
It is porous (semi-permeable) allows molecules to pass through and it contain receptor proteins
that allows to detect external signaling molecules such as hormones.
Nucleus
It is large oval body near the center of the cell. It has nuclear pores and surrounded by nuclear
membrane. It contains chromosomes – consist of DNA wrapped around proteins.
It is the control center for all activity of the cell including metabolisms, protein synthesis, growth
and reproduction (cell division). It stores genetic materials.

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Mitochondria
The power house of the cells or generator of the cells. Mitochondria are self-replicating
organelles that occur in various numbers, shape, and size in the cytoplasm of eukaryotic cells.

Respiration occurs in the cell mitochondria (oxidative phosphorylation using oxygen to release
energy stored in cellular nutrients).
Ribosomes
Tiny spherical bodies that help make proteins. It is found in the cytoplasm or attached to the
endoplasmic reticulum and it help make the proteins.
Golgi bodies or apparatus
Tube like structures that have tiny sacs at their ends. They help in packaging, storing and
processing of protein.
Lysosomes
It is also called “suicide sacs” small structures that contain enzymes which are used in digestion.
If lysosome were to burst it could destroy the cell.
Endoplasmic reticulum
It is a transport network for molecules targeted for certain modifications and specific
destinations, as compared to molecules that float freely in the cytoplasm. It has two forms: the
rough endoplasmic reticulum which has ribosomes on its surface that secrete protein into
endoplasmic reticulum.
And smooth endoplasmic reticulum, which lacks ribosomes. The smooth endoplasmic
reticulum plays a role in calcium sequestration and release.

Lecture 3

TRANSPORT ACROSS CELL MEMBRANE

Each is enclosed by its plasma membrane, which provides a selective barrier to substances
entering or leaving the cellular environment. This property is called selective permeability,
allows the cell (plasma) membrane to control the entry or exit if many substances, thereby
regulating the composition of its internal environment.

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Particle size is important, as many small molecules, e.g. water, can pass freely across the
membrane by simple diffusion, while large molecules cannot and may therefore confined to
either the interstitial fluid or the intracellular fluid.
Selective permeability ensures that the chemical composition of the fluid inside cells is different
from the interstitial fluid that bathes them.
Pores or specific channels in the plasma membrane admit certain substances but not others.
Membrane is also studded with specialized pumps or carriers that import or export specific
substances.
ACTIVE TRANSPORT
This is the transport of substances up their concentration gradient from a lower to a higher
concentration. Therefore, chemical energy in the form of adenosine triphosphate (ATP), derives
specialized protein carrier molecules that transport substances across the membrane in either
direction.
PASSIVE TRANSPORT
This occur when substances can cross the semipermeable membrane and organelle membranes,
and move down the concentration gradient without using energy.
DIFFUSION
Is the movement of molecules from an area of high concentration to an area of low
concentration, and occurs mainly in gases, liquids, and solutions. Diffusion can also occur across
semipermeable membranes such as cell membrane of capillaries wall.
FACILITATED DIFFUSION
This passive process is used by some substances that unable to diffuse through the
semipermeable membrane unaided. E.g. glucose, amino acids molecules.
Specialized protein carrier molecules in the membrane have specific sites that attract and bind
substances to be transferred, like lock and key mechanism.
OSMOSIS
Is a process that involve passive movement of water down its concentration gradient towards
equilibrium across a semipermeable membrane
BULK TRANSPORT
This refers to the transfer of particles too large to cross the cell membranes occur by pinocytosis
(“cell-drinking”) or phagocytosis (“cell-eating”). These particles are engulfed by extensions of
the cytoplasm, which enclose them, forming a membrane-bound vacuole. Pinocytosis allows the
cell to bring in fluid.

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 BODY TISSUE AND FUNCTIONS
In complex organisms such as the human body, cells with similar structures and functions are
found together, forming the tissues of the body consist of large numbers of cells. They are
classified according to the size, shape and functions of these cells. There are four (4) main types
of tissue, each of which has subdivisions. They are:
1. Epithelial tissue or epithelium
2. Connective tissue
3. Muscle tissue
4. Nervous tissue.

A) Epithelial tissue
This group of tissues is found covering the body and lining cavities and tubes. It is also found in
glands. The structure of epithelium is closely related to its functions which include:

- Protection of underlying structures from, for example, dehydration, chemical and

mechanical damage
- Secretion
- Absorption

Epithelial tissue, based on layers may be:

- Simple: a single layer of cells
- Stratified: several layers of cells
- Pseudo stratified epithelium
- Transitional epithelium
Note: Cellular forms may be Squamous, Cuboidal, and Columnar epithelium
B) Connective tissue
Connective tissue is the most abundant tissue in the body. The cells forming the connective
tissues are more widely separated from each other than those forming the epithelium, and
intercellular substance (matrix) is present in considerably larger amounts. Based on the cells
present and the extracellular matrix we have two (2) types of connective tissue:

a. Connective tissue proper: It is further subdivided into

- Dense connective tissue: it contains more fibers and fewer cells than loose
connective tissue.it connects and support other structures in the body e.g. ligaments,
cartilages, bones and tendon.

- Loose connective tissue (areolar tissue): this is the most generalized type of
connective tissue. It is found in almost every part of the body, providing elasticity and
tensile strength. It connects and support other tissues, example:- under the skin,
between muscles, supporting blood vessels and nerves, in the alimentary canal and in
the glands supporting secretory cells.

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 b. Specialized connective tissue: reticular tissue, Blood, and Adipose tissue

Major functions of connective tissue are: Binding and structural support, Protection,
Transport, Insulation etc.

C) Muscle tissue
This tissue is able to contract and relax, providing movement within the body and of the body
itself. Muscle contraction requires a rich blood supply providing sufficient oxygen, calcium and
nutrients and removing waste products. There are three types of muscle tissue, which consists of
specialized contractile cells:
- Skeletal muscle
- Smooth muscle
- Cardiac muscle.

a) Skeletal muscle tissue

This may be described as skeletal, striated, striped or voluntary muscle. It is called voluntary
because contraction is under conscious control.

b) Smooth (visceral) muscle tissue

Smooth muscle may also be described as non-striated or involuntary. It is not under
conscious control. It is found in the walls of hollow organs:
- Regulating the diameter of blood vessels and parts of the respiratory tract
- Propelling contents of the ureters, ducts of glands and alimentary tract
- Expelling contents of the urinary bladder and uterus.

c) Cardiac muscle tissue

This type of muscle tissue is found exclusively in the wall of the heart. It is not under
conscious control but, when viewed under a microscope, cross-stripes characteristic of
voluntary muscle can be seen. Each fiber (cell) has a nucleus and one or more branches.

D) Nervous tissue
Is the main component of the nervous system, which includes the brain, spinal cord, and nerves.
It is one of the four major classes of tissues. It is specialized tissue found in central nervous
system and the peripheral nervous system, it consists of neurons and supporting cells called
neuroglia.

Neurons: Are highly specialized nerve cells that generate and conduct nerve impulses.
Neuroglia: Are supporting cells that provide physical sport, remove debris, and provide
electrical insulation.

The above cells mentioned were also categorized into the following types; two types of nervous
tissue are found in the nervous system:
 Excitable cells: these are called neurons and they initiate, receive, conduct and transmit
information.
 Non- Excitable cells: these are also known as glial cells and they support the neurons.

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Nervous tissue involves in integration and communication processes.
Lecture 4
CELL DIVISION, MITOSIS AND MEIOSIS, MUTATION
Cell division involves the distribution of identical genetic material, DNA, to two (2) daughters’
cells. What is most remarkable is the beauty with which the DNA is passed along, without
dilution or error, from one generation to the other. Cell division function in reproduction, growth
and respiration.
SOME OF THE TERMS USED FOR CELLULAR DIVISION AND GENETICS
In order to understand the concept of cell division and genetics some basic definitions are in
order:
a) Gene: is the basic unit of heredity; codes for specific trait (trait)
b) Somatic cell: all cell body except reproductive cells
c) Gamete: reproductive cells (sperm and egg)
d) Chromosome: elongated cellular structure composed of DNA and protein.
e) Diploid (2n): cellular condition where each chromosome type is represented by two
homologous chromosomes
f) Haploid (n): cellular condition where each chromosome type is represented by only one
chromosomes
g) Centromere: region of chromosome where microtubules attach during mitosis and meiosis

MITOSIS
This is the distribution of two sets of chromosomes into two separate and equal nuclei following
the replication of the chromosome of the parent nucleus. Mitosis is divided into four stages I:
Prophase: in this phase the chromosome become clear and distinct, the chromosomes have
been replicated, mitotic apparatus appear, and centrioles separate to opposite poles and
nuclear membrane disappear.
Metaphase: the chromosomes line up at the equator of the cell on the mitotic spindle of
apparatus.
Anaphase: the centromeres separate and one of each pair sister chromatids migrate to each
end of the cell.
Telophase: the mitotic spindle disappears, the chromosomes uncoil and the nuclear
envelope reforms.
Characteristics of Mitosis
- It involves one cell division
- Two (2) daughter cells are produced
- Daughter cells are identical to parent cells and also to one another

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- The number of chromosome is unchanged
- It takes place in somatic cells

MEIOSIS
This is a type of cell division that involves two distinct cell divisions which are meiosis I and
meiosis II. It occurs in four stages namely:
Prophase I, Metaphase I, Anaphase I, and Telophase I
Characteristics of Meiosis
- It involves two cell divisions
- Four daughter cells are produced
- Daughter cells are not identical to parent cell and also to one another
- The number of chromosomes is reduced by half
- It takes place in sex cells.

MUTATION
This means a hereditable alteration in the normal genetic make-up of a cell. Most mutation occur
spontaneously because of the countless millions of DNA replications and cell divisions that
occur normally throughout life.
Others may be external factors, such as X-rays, ultraviolet rays or exposure to certain chemicals.
Any factor capable of mutating DNA is called a mutagen.

Lecture 5

BODY FLUID CHEMISTRY

Body is formed by solids and fluids. Fluid part is more than two third of the whole body. Water
forms most of the fluid part of the body. In human beings, the total body water varies from 45%
to 75% of body weight.

In a normal young adult male, body contains 60% to 65% of water and 35% to 40% of solids. In
a normal young adult female, the water is 50% to 55% and solids are 45% to 50%. In females,
water is less because of more amount of subcutaneous adipose tissue.

In thin persons, water content is more than that in obese persons. In old age, water content is
decreased due to increase in adipose tissue. Total quantity of body water in an average human
being weighing about 70kg is about 40L.

Important of Body Fluids

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1. In transport mechanism
2. In metabolic reactions
3. In homeostasis
4. In temperature regulation

Body Fluid Compartments and its distributions

Total water in the body is about 40 L. It is distributed into two (2) major compartments:

Intracellular fluid (ICF): Its volume is 22L and it forms 55% of the total body water. The
composition of intracellular fluid is largely controlled by the cell itself because there are
selective uptake and discharge mechanisms present in the cell membrane.

Extracellular fluid (ECF): Its volume is 18L and it forms 45% of the total body water. This
consists mainly of blood, plasma, lymph, CSF, and fluid in the interstitial space of the body.

Other extracellular fluids are presents in very small amounts; their role is mainly in lubrication,
and they include joints (synovial) fluid, pericardial fluid around the heart, and pleural fluid
around the lungs.

Extracellular fluid is divided into five (5) subunits:

1. Interstitial fluid and lymph (20%)
2. Plasma (7.5%)
3. Fluid in bones (7.5%)
4. Fluid in dense connective tissues like cartilage (7.5%)
5. Transcellular fluid (2.5%)

Transcellular fluid (2.5%)

These are also called specialized body fluids; Cerebrospinal fluid, intraocular fluid, Digestive
juices, Serous fluid, intrapleural fluid, pericardial fluid and peritoneal fluid, Synovial fluid in
joints and Fluid in urinary tract.

Lecture 6

CAVITIES OF THE BODY

The major cavities of the human body are the spaces left over when internal organs are removed.
There are additional body cavities which we only discuss in lecture; the organs that make up the
systems of the body are contained in four cavities:
Cranial cavity
Thoracic cavity
Abdominal cavity
Pelvic cavity

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Cranial cavity: This contains the brain and its boundaries are formed by the bones of the skull.
Anteriorly Frontal bone

Laterally 2 temporal bone

Posteriorly 1 occipital bone

Superiorly 2 parietal bone

(roof)

Inferiorly 1 sphenoidal & 1 ethmoidal bone

(base or and parts of the frontal, temporal
floor) and occipital bones

Thoracic cavity: This cavity is situated in the upper part of the trunk. Its boundaries are formed
by a bony framework and supporting muscles.

Anteriorly The sternum and costal cartilages of the ribs

Posteriorly The thoracic vertebrae and the intervertebral discs between the bodies of the
vertebrae

Laterally 12 pairs of the ribs and the intercostal muscles

Superiorly The structures forming the root of the neck

Inferiorly The diaphragm, a dome-shaped muscle

Contents: The main organs and the structures contained in the thoracic cavity are trachea, two
bronchi, two lungs, the heart, aorta, superior and inferior vena cava, numerous other
neurovascular structures and esophagus.

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Abdominal cavity: This is the largest cavity in the body and is oval in shape. It is situated in the
main part of the trunk and its boundaries are:

Anteriorly The muscles forming the anterior abdominal wall

Posteriorl The lumbar vertebrae and muscles forming the posterior wall
y

Superiorly The diaphragm which separates it from the thoracic cavity

Inferiorly The pelvic cavity with which it continuous

Laterally The lower ribs and parts of the muscles of the abdominal wall

By convention, the abdominal cavity is divided into the nine (9) quadrants or regions shown in
the below figure. This facilitates the description of the positions of the organs and structures it
contains:

Contents: Most of the space in the abdominal cavity is occupied by the organs and glands
involved in the digestion and absorption of food. These are:

The stomach, small intestine and most of the large intestine, The liver, gall bladder, bile ducts
and pancreas. Other structures include; spleen, two kidneys, and the upper part of the ureters,
two adrenal (suprarenal) glands, and numerous neurovascular and lymphatic structures.

Pelvic cavity: The pelvic cavity is roughly funnel shaped and extends from the lower end of the
abdominal cavity. The boundaries are:

Anteriorly The pubic bones

Posteriorly The sacrum and coccyx

Laterally The innominate bones

Superiorly It is continuous with the abdominal cavity

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 Inferiorly The muscles of the pelvic floor

Contents: The pelvic cavity contains the following structures; the sigmoid colon, rectum and
anus some loops of the small intestine, urinary bladder, lower parts of the ureters and the urethra.

In the female, the organs of the reproductive system include the uterus, uterine tubes, ovaries and
vagina. In the male reproductive system some of the organs include the prostate gland, seminal
vesicles, spermatic cords, vas deferens, ejaculatory ducts and the urethra (common to the urinary
system).

Lecture 7

CONCEPT OF ADAPTATION AND HOMEOSTASIS

Introduction
Homeostasis is the ability of living systems to maintain a steady and uniform internal
environment to allow the normal functioning of the systems.

Homeostasis is mainly involved in managing various internal variables of the living system like
body temperature, pH of various fluids, the concentration of different ions, and the body sugar
level. A number of regulatory mechanisms are employed to resist changes in the body against
environmental and bodily factors. Homeostasis can be maintained by separate organs or by the
entire body at once.

How to maintain Homeostasis

Homeostasis is maintained by a complex system that consists of individual units working in a
particular sequence to balance a given variable. All homeostasis mechanisms consist of four
regulating device which regulate in a cyclic manner. This includes which:
1. Stimulus: The stimulus is something that results in changes within the system involving the
variable.
2. Receptor: is the sensing unit of homeostasis, where it monitors and responds to the changes
in the body. The changes in the system are realized by the sensor, which then sends the
information to the control unit.
3. Control unit: Once the information is sent to the control unit, it tallies the changed value to
its normal value. If the value is different from the normal value, the control center activates
the effectors against the stimulus.
4. Effector: The effectors can be muscles, organs, glands, or other similar structures that are
activated as a result of the signal from the control unit. An effector is a target which is acted
upon by the control unit to bring the value of variable back to normal. The effector
essentially counteracts the stimulus to nullify its effect.

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Feedback mechanism: Is a biological system that helps to maintain homeostasis where the result of the
system either enhances the system (positive feedback) or inhibits the system (negative feedback).
There are two (2) types of feedback mechanisms that assist the process of homeostasis:
a) Negative feedback mechanism: Most homeostatic processes are maintained by negative
feedback loops. Negative feedback mechanism result in an output that tends to minimize the
effect of the stimulus in order to stabilize the system. These loops tend to counteract the stimulus
and act against the stimulus that might have triggered the system.

Negative feedback loops are activated under two conditions;

- In the first case, the activation is caused when the value of a variable (like body
temperature) is above its normal value and thus has to be brought back down.
- Under the other conditions, the activation is caused when the value of the variable is
below the normal value and thus has to be brought back up.

Example: the production of RBCs by the kidneys when the decreased level of oxygen is sensed
in the body.

Positive feedback mechanism: Some biological and natural systems might utilize positive
feedback loops where the output of the mechanism tends to increase the effect of the stimulus.

This mechanism is generally observed in processes that need to happen quickly and towards
completion. Thus, positive feedback mechanism tend to move the process towards completion
rather than towards equilibrium.

Example: the process of childbirth. In this case, as the baby’s head pushes the cervix, the
neurons in that region are activated. This causes the brain to send signals to produce oxytocin
which further increases the uterine contractions putting more pressure on the cervix, facilitating
childbirth.

Types of Homeostasis regulation

Thermoregulation
Osmoregulation
Chemical regulation
Acid-Base Homeostasis
Blood pressure homeostasis etc.

Application of Homeostasis

1. Homeostasis is a necessary process that maintains the internal environment of living beings
at optimum levels so that normal physiological processes can take place smoothly.
2. As a result of homeostasis, the metabolic reactions are controlled by enzymes.
3. Homeostasis allows the body to function even when the environment and other factors
change.

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 Lecture 8
BLOOD AND ITS COMPOSITION

Blood is a connective tissue in fluid form. It is considered as the ‘fluid of life’ because it carries
oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the
lungs. It is known as ‘fluid of growth’ because it carries nutritive substances from the digestive
system and hormones from endocrine gland to all the tissues.

The blood is also called the ‘fluid of health’ because it protects the body against the diseases
and gets rid of the waste products and unwanted substances by transporting them to the excretory
organs like kidneys.

Blood makes up about 7% of body weight in adults the body contains 5 to 6 litres of blood in a
70kg man. This proportion is less in women and considerably greater in children, gradually
decreasing until the adult level is reached.

PROPERTIES OF BLOOD

- Color: Blood is red in color. Arterial blood is scarlet red because it contains more
oxygen and venous blood is purple red because of more carbon dioxide.

- Volume: Average volume of blood in a normal adult is 5L. In a newborn baby, the
volume is 450ml. It increases during growth and reaches 5L at the time of puberty. In
females, it is slightly less and is about 4.5L. It is about 8% of the body weight in a
normal young healthy adult, weighing about 70kg.

- Reaction and pH: Blood is slightly alkaline and its pH in normal conditions is 7.4

- Specific gravity: Specific gravity of total blood : 1.052 to 1.061,Specific gravity

blood cells : 1.092 to 1.101, Specific gravity of plasma : 1.022 to 1.026

- Viscosity: Blood is five times more viscous than water. It is mainly due to red blood
cells and plasma proteins.

BLOOD COMPOSITION
Blood contains the blood cells which are called formed elements and the liquid portion known as
plasma.

1. Blood Cells
Three types of cells are present in the blood:
 Red blood cells or erythrocytes

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  White blood cells or leukocytes
 Platelets or thrombocytes.

PLASMA
Plasma is a straw-colored clear liquid part of blood. It contains 91% to 92% of water and 8% to
9% of solids (are the organic and the inorganic substances). This is mainly water with a wide
range of substances dissolved or suspended in it. These include:
o Nutrients absorbed from the alimentary canal
o Oxygen absorbed from the lungs
o Chemical substances synthesized by body cells, e.g. hormones
o Waste materials produced by all cells to be eliminated from the body by
excretion.

Blood cells
There are three distinct groups, classified according to their functions:
1. Erythrocytes (red blood cells) transport oxygen and, to a lesser extent, carbon dioxide
between the lungs and all body cells.

2. Leukocytes (white blood cells) are mainly concerned with protection of the body against
infection and foreign substances. There are several types of leukocytes, which carry out their
protective functions in different ways.

3. Platelets (thrombocytes) are tiny cell fragments that play an essential part in blood clotting.

HAEMOPOIESIS
This is the process of blood cell formation. Blood cells are synthesized mainly in the red bone
marrow. Some lymphocytes are produced in lymphoid tissues.

Stem cells called haemocytoblast and they go through several developmental stages before
entering the blood different types of blood cells follow separate lines of development.

ERYTHROPOIESIS
This is the process of the origin, development and maturation of erythrocytes.

FUNCTIONS OF BLOOD

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1. Nutritive Function
Nutritive substances like glucose, amino acids, lipids and vitamins derived from digested food
are absorbed from gastrointestinal tract and carried by blood to different parts of the body for
growth and production of energy.

2. Respiratory Function
Transport of respiratory gases is done by the blood. It carries oxygen from alveoli of lungs to
different tissues and carbon dioxide from tissues to alveoli.

3. Excretory Function
Waste products formed in the tissues during various metabolic activities are removed by blood
and carried to the excretory organs like kidney, skin, liver, etc. for excretion.

4. Transport of Hormones and Enzymes

Hormones which are secreted by ductless (endocrine) glands are released directly into the blood.
The blood transports these hormones to their target organs/tissues. Blood also transports
enzymes.

5. Regulation of Water Balance

Water content of the blood is freely interchangeable with interstitial fluid. This helps in the
regulation of water content of the body.

6. Regulation of Acid-Base Balance

Plasma proteins and hemoglobin act as buffers and help in the regulation of acid-base balance

7. Regulation of Body Temperature

Because of the high specific heat of blood, it is responsible for maintaining the thermoregulatory
mechanism in the body, i.e. the balance between heat loss and heat gain in the body.

8. Storage Function
Water and some important substances like proteins, glucose, sodium and potassium are
constantly required by the tissues. Blood serves as a readymade source for these substances.
And, these substances are taken from blood during the conditions like starvation, fluid loss,
electrolyte loss, etc.

9. Defensive Function
Blood plays an important role in the defense of the body. The white blood cells are responsible
for this function. Neutrophils and monocytes engulf the bacteria by phagocytosis. Lymphocytes
are involved in development of immunity. Eosinophil are responsible for detoxification,
disintegration and removal of foreign proteins.

COAGULATION OR CLOTTING
This is defined as the process in which blood loses its fluidity and becomes a jelly-like mass few
minutes after it is shed out or collected in a container.

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FACTORS INVOLVED IN BLOOD CLOTTING
Coagulation of blood occurs through a series of reactions due to the activation of a group of
substances. Substances necessary for clotting are called clotting factors. In this process blood can
be clot through a number of stages and these are:
 Formation of thromboplastin
 Conversion of prothrombin to thrombin
 Conversion of fibrinogen to fibrin
 Finally, the blood clot

BLOOD PRESSURE
This can be defined as the force exerted by the blood as it presses against and attempts to stretch
the blood vessels especially artery.

PULSE
This is the rhythmical expansion and recoil of the elastic arteries caused by the ejection of blood
from the left ventricles.

ABO BLOOD GROUPS

Determination of ABO blood groups depends upon the immunological reaction between antigen
and antibody. Landsteiner found two antigens on the surface of RBCs and named them as A
antigen and B antigen. These antigens are also called agglutinogens because of their capacity to
cause agglutination of RBCs. He noticed the corresponding antibodies or agglutinins in the
plasma

ABO SYSTEM
Based on the presence or absence of antigen A and antigen B, blood is divided into four groups:
1. A group
2. B group
3. AB group
4. O group.
Blood having antigen A belongs to ‘A’ group. This blood has β-antibody in the serum. Blood
with antigen B and α-antibody belongs to ‘B’ group. If both the antigens are present, blood group
is called ‘AB’ group and serum of this group does not contain any antibody. If both antigens are
absent, the blood group is called ‘O’ group and both α and β antibodies are present in the serum

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 Lecture 9

INTRODUCTORY NOTE ON CARDIOVASCULAR SYSTEM

The circulatory or vascular system is divided into two main parts for descriptive purposes. They
are namely

1. The cardiovascular system or blood circulatory system, consisting of the heart which acts
pump, and the blood vessels through which the blood circulates.
2. The lymphatic system, consisting of lymph nodes and lymph vessels through which
colourless lymph flows.
Note: the two systems communicate with one another and are intimately associated.

Cardiovascular System and the Components of the Cardiovascular System

The components of the cardiovascular system are:
 Heart
 Blood
 Blood vessel arteries, vein, and capillaries

FUNCTION OF THE COMPONENTS OF THE CARDIOVASCULAR SYSTEM

1. Arteries and Arterioles: These are the blood vessels that transport blood away from the
heart.
2. Veins and Venules: These are the blood vessels that return or transport blood to the heart
3. Capillaries: The capillaries are responsible for exchange of substances between the
blood and the tissue fluid that bath the cells of the body.
4. Heart: The heart is the organ which pumps the blood round the body.
5. Blood: The liquid part that is responsible for the transportation of substances and
materials round the body.

STRUCTURE OF THE COMPONENTS OF THE CARDIOVASCULAR SYSTEM

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 1. Arteries and Arterioles: They are hollow structures whose walls are composed of the
three layers of tissue and they lack valves.
2. Veins and Venules: The veins are hollow structures whose walls are composed of three
layers of tissue but they have valves.
3. Capillaries: These also have walls that consists of a single layer of endothelial cells.
They are the smallest blood vessels where nutrients and wastes are exchanged, and then
combine with other vessels that exit capillaries to form venules, small blood vessels that
carry blood to a vein, a larger blood vessel that returns blood to the heart.

Blood: This can be defined as a red viscous connective tissue fluid whose cells are suspended in
a liquid intercellular material and flows round the body.

DIFFERENCES BETWEEN ARTERIES AND VEINS

ARTERIES VEINS

The walls are thicker The walls are thinner

Carries blood under high pressure Carries blood under low pressure

Carries oxygenated blood except the Carries deoxygenated blood except the
pulmonary vein pulmonary arteries

Carries blood away from the heart Carries blood towards the heart

May not possess valves Some possess valves

The smallest arteries are called arterioles The smallest veins are called venules

HEART
The heart is roughly cone-shaped hollow muscular organ. It is about 10cm long and is about the
size of the owner’s fist. It weighs about 225g in women and 310g in men.

The heart lies in the thoracic cavity in the mediastinum (the space between the two lungs). It lies
obliquely, a little more to the left than right. It has a base and apex and is composed of three
layers of tissue in its wall namely.
Pericardium, Myocardium and Endocardium

The chambers of the Heart have two basic part the Ventricles and Atria and these includes:
Right ventricle & Right atrium
Left ventricle & Left atrium

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 Human Heart

The heart is associated with large blood vessels known collectively as great vessels of the heart.
They include:-
Subclavian artery, Right and left common carotid arteries, Brachiocephalic artery,
Superior and Inferior vena cava, Pulmonary artery, Pulmonary veins and Aorta.

DIVISIONS OF CIRCULATION
Blood flows through two divisions of circulatory system:
1. Systemic circulation
2. Pulmonary circulation.
1. Systemic circulation:
The presence of oxygenated blood in the left ventricle marks the beginning of systemic
circulation though it is continues. The blood pumped out of the ventricle enters the aorta and
carried by branches of the aorta to various parts of the body.

After the cells of the body utilizes or used up the oxygen and produce carbondioxide the blood
becomes deoxygenated. The superior vena cava (SVC) then transports the deoxygenated blood
from the upper part of the body to the right atrium and the inferior vena cava (IVC) then
transports the deoxygenated blood from the lower part of the body to the right atrium and the
cycle continuous.

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2. Pulmonary circulation:
This is the circulation of blood between the heart and the lungs. During pulmonary circulation,
deoxygenated blood in the right atrium flows into the right ventricle through the tricuspid valve
and from here; it is pumped through the pulmonary trunk and pulmonary arteries which transport
the deoxygenated blood to the lungs for oxygenations

COMMON CONDITIONS THAT AFFECT THE CARDIOVASCULAR SYSTEM

 Shock: this occurs when there is a reduction in the amount of blood circulating, in the
blood pressure and cardiac output.
 Hypertension: this is used to describe blood pressure that is sustainably higher that the
generally accepted “normal” maximum level for a particular age or group.
 Cardiac failure: the heart is described as failing when cardiac output is unable to
maintain the circulation of sufficient blood to meet the needs of the body.

Lecture 11

INTRODUCTORY NOTES ON THE LYMPHATIC SYSTEM

The immune system is the complex collection of cells and organs that destroys or neutralizes
pathogens that would otherwise cause disease or death. The lymphatic system, for most people,
is associated with the immune system to such a degree that the two systems are virtually
indistinguishable.

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The lymphatic system is the system of vessels, cells, and organs that carries excess fluids to the
bloodstream and filters pathogens from the blood.

The swelling of lymph nodes during an infection and the transport of lymphocytes via the
lymphatic vessels are but two examples of the many connections between these critical organ
systems.

COMPONENTS OF THE LYMPHATIC SYSTEM

The components of the lymphatic system include: Lymph, Lymph node, Lymph vessels,
Lymphatic organs e.g. Spleen and thymus, Diffuse lymphoid tissues e.g. Tonsils

LYMPH
Is a clear watery fluid, similar in composition to plasma, with the important exception of plasma
proteins, and identical in composition to interstitial fluid.

Lymph transports the plasma proteins that escaped from capillary beds back to the bloodstream.
It also carries away larger particle e.g. bacteria, and cell debris from damage tissues, which can
then be filtered out and destroyed the lymph

Lymph contains lymphocytes (defense cells), which circulates in the lymphatic system and patrol
the different regions of the body. In the lacteal of the small intestine, fats absorbed into the
lymphatic’s give the lymph (now called chyle), a milky appearance

LYMPHATIC CAPILLARIES:
The lymphatic capillaries originate as blind-ended tubes in the interstitial spaces. They have the
same structure as blood capillaries i.e. a single layer of epithelial cells, but their walls are more
permeable to all interstitial fluid constituents, including proteins and cell debris. The tiny
capillaries join up to form larger lymph vessels.

FUNCTION OF LYMPHATIC CAPILLARIES

The lymphatic capillaries function in the drainage of excess tissue fluid from the intercellular
spaces.

Larger Lymph Vessels:

Lymphatic vessels are often found running alongside the arteries and veins servicing the area.
The wall of the large lymphatic vessels are about the same thickness as those of small veins and
have the same layers of tissue, i.e. a fibrous covering, a middle layer of smooth muscle and
elastic tissue and an inner lining of endothelium.

Like veins, lymphatic vessels to ensure that lymph flow in a one-way direction towards thorax.
The lymphatic vessels do not have a ‘pump’ like the heart of the cardiovascular system,
involved in the onward movement of lymph, but the muscle layer in the walls of the large
lymphatic vessels has an intrinsic ability to contract rhythmically (the lymphatic pump).

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Lymphatic vessels become larger as they join together eventually forming two large ducts, the
thoracic duct and the right lymphatic duct which empty lymph into the subclavian vein.

The other factors believed to assist in the onward movement of lymph towards the thorax
include:
 Tissue fluid pressure
 Contraction of surrounding muscles
 Pressure caused by pulsation of adjacent arteries
 Negative pressure in the thorax during inspiration.

FUNCTION OF LYMPHATICS VESSELS

a) Return of excess tissue fluid to the blood (3 - 4 litres daily)
b) Return of plasma proteins to the blood
c) Transport of other particulate materials to lymph nodes for breakdown
d) Fat absorbed in the small intestine enters lymph capillaries called lacteals which transport
the low milky fluid, called chyle to the thorax.

LYMPH NODE:
Lymph nodes are oval or bean-shaped organs that like often in group, along the length of lymph
vessels in strategic position throughout the body. The lymph drains through a number of lymph
nodes, usually 8 – 10, before returning to the venous circulation. The lymph nodes vary
considerably in size: some are as a pin head and the largest are about the size of the almonds.

Lymph nodes have an outer capsule of fibrous tissue that dips into the lymph node substance
forming partitions or trabeculae. The lymph nodes consist of reticular and lymphatic tissue
containing many lymphocytes and macrophages.

Four or three afferent lymph vessels may enter a lymph node while only one efferent vessel
carries lymph away from the node. Each lymph node has a concave surface called the hilum
where structures enter and leave the lymph node.

FUNCTIONS OF LYMPH NODE:

1. Filtering and phagocytosis: lymph is filtered by the reticular and lymphatic tissues as it
passes through the lymph nodes. The particulate materials here include: bacteria, dead and live
phagocytes containing ingested microbes, cells from malignant tumors, damage tissues cell and
inhaled particles.

Organic materials are destroyed in the lymph node by macrophages and antibodies. Materials
that are not filtered out and destroyed in one lymph node will pass on to successive lymph node
until the lymph is cleared of foreign matters and cell debris which is ready to enter the blood.

In some case where phagocytosis of bacteria is incomplete, that may stimulate inflammation and
enlargement of the lymph node (lymphadenopathy).

2. Proliferation of lymphocytes: Activated T and B lymphocytes multiply in lymph nodes. An

antibody produced by sensitized B-lymphocytes enters lymph and blood draining the nodes.

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SPLEEN:
The spleen is formed by reticular and lymphatic tissues and is the largest lymph organ. The
spleen lies in the left hypochondriac region of the abdominal cavity between the fundus of the
stomach and the diaphragm. It is purplish in colour and varies in size in different individuals, but
is usually about 12cm long, 7cm wide and 2.5cm thick. It weighs about 200g.

The spleen is slightly oval in shape with the hilum on the lower medial border, and is enclosed in
a fibroelastic capsule that dips into the organ, forming trabeculae.

FUNCTIONS OF THE SPLEEN

1. Phagocytosis: old and abnormal erythrocytes are destroyed in the spleen and breakdown
products, bilirubin and iron, are passed to the liver via the splenic and portal vein. Other cellular
materials e.g. leukocytes, platelets and microbes, are phagocytosed in the spleen.

Unlike lymph nodes, the spleen has no efferent lymphatic entering it so it is not exposed to
diseases spread by lymph.

2. Development of lymphocytes: the aggregates of lymphocytes respond to antigens by immune

reactions. Sensitized B and T-lymphocytes multiply and become immuno competent. Some B
lymphocytes develop into plasma cells and produce antibodies. The spleen provides many of the
lymphocytes in the blood.

3. Erythropoiesis: the spleen and liver are important sites of fetal blood cells productions, and
the spleen can also fulfill this function in adults in times of great need.

4. Storage of blood: The spleen contains up to 350ml of blood and in response to sympathetic
stimulation can return most of this volume of blood to the circulation e.g. in hemorrhages

THYMUS GLAND:
The thymus gland lies in the upper part of the mediastinum behind the sternum and extends
upward into the root of the neck. It weighs about 10 to 15g at birth and growth until the
individual reaches puberty, when it begins to atrophy. Its’ maximum weight at puberty is
between 30 – 40g and by middle age it has returned to approximately its weight at birth.

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 Thymus gland

FUNCTION OF THE THYMUS GLAND

a) Some lymphocytes that originate from the stains cell in the red bone marrow enters the
thymus and develop into activated T-lymphocytes. The thymic processing produces
mature T-lymphocytes that can distinguish self-tissue from foreign tissue, and also
provides each T-lymphocyte with the ability or react to only one specific antigen from the
millions it will encounter. These lymphocytes will now leave the thymus and enters the
bloodstream.
b) The epithelial cell of thymus gland releases a hormone called ‘thymosin’ which
stimulates the maturation of the thymus and other lymphoid tissues.

Circulation of Lymph
Following the entry of excess tissue fluid into the lymphatic capillaries forming lymph in various
parts of the body, the lymph passes through vessels of increasing size and a varying number of
lymph nodes before returning to the blood at the subclavian vein.

Other Lymphatic Tissue:

Lymphatic tissue; is found in a number of situations in the body in addition to lymph nodes.
a) Palatine tonsil between the mouth and oral part of the pharynx
b) Pharyngeal tonsil- on the wall of the nasal part of the pharynx
c) Solitary lymphatic follicles
d) Aggregated lymphatic follicles in the wall of the small intestine
e) Vermiform appendix- an outgrowth from the caecum (first part of large intestine)

FUNCTION OF THE LYMPHATIC SYSTEM

 The primary function of the lymphatic system is to return excess tissue fluid and plasma
proteins back to the blood.
 The lymphatic system is also involved in the specific and non-specific defense
mechanism of the body, i.e. phagocytosis and the maintenance and development of
immunity.

A major function of the lymphatic system is to drain body fluids and return them to the
bloodstream. Blood pressure causes
leakage of fluid from the capillaries, resulting in the accumulation of fluid in the interstitial space
—that is, spaces between individual cells in the tissues.

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