Histology

Tissue

- Group of cells with similar structure and

function, plus the extracellular
substance surrounding them.

Histology
- Study of tissues
Types of Tissues
Epithelial
- Functions
- Covering or lining of tissue o Protects underlying
structures
Connective o Acts as barrier
- Diverse primary tissue type o Permits passage of substance
- Makes up part of every organ o Secretes substance
o Absorption of substance
Muscle - Classification
- Tissue that contract or shorten o classified primarily according
to the number of cell layers
Nervous and the shape of the
- Coordinating and controlling body superficial cells.
activities o Cell layers
▪ Simple, stratified, or
EPITHILIAL TISSUES pseudostratified
- Epithelium o Cell shape
- Cover and protect both inside and ▪ Squamous, cuboidal,
outside columnar, or
- Under epithelial transitional shape
o Exocrine gland varies with the degree
o Endocrine gland of stretch
- Characteristics Layers of epithelium
o Mostly composed of cells
o Covers body surface - Simple
o Distinct cell surface o Single layer of cells
o Cell and matrix connection o each cell extending from the
o Nonvascular basement membrane to the
o Capable or regeneration free surface
- stratified
o more than 1 layer of cells
 o only basal layer attaches the Simple cuboidal
deepest layer to the
- single layer of cubelike
basement membrane
- carries out active transport,
- pseudostratified columnar
facilitated diffusion, or secretion
o special type of special
- have greater secretory capacity than
epithelium
simple squamous
o appears to be falsely
stratified
o one layer of cells, all cells
attached to the basement
membrane
o Due to variations in the shape
of the cells, the epithelia
appear stratified.
Shapes of epithelium
- Squamous Simple columnar
o Flat or scalelike
- Cuboidal - single layer of tall, thin cells
o Cube shape - large size of these cells enables them
- Columnar to perform complex functions, such
o Taller than wide as secretion.
- small intestine produces and
secretes mucus and digestive
Simple squamous enzymes.

- Single layer of thin flat cell

- Some substance can pass through,
but some cannot
- LUNGS
o allows for gas exchange
- KIDNEY
o helps filter wastes from the
blood while keeping blood
cells inside the blood vessels.
Pseudostratified columnar Stratified cuboidal
- secretes mucus, which cover its free - Consist of more than 1 layer of
surface cuboidal
- cilia in the airway move the mucus - rare and is found in sweat gland
and accumulated debris towards the ducts, ovarian follicular cells, and the
throat, where it is swallowed salivary glands.
- Function
o Absorb
o Secret
o Protect
Stratified columnar
- Consist of more than one layer of
columnar
- The surface cells are columnar but
Stratified squamous
the deeper cells are irregular or
- consist of several thick layers cuboidal in shape.
- 2 types of stratified squamous - mammary gland ducts, the larynx,
o Keratinized and a portion of the male urethra.
o Non keratinized - Function
o Carries out secretion,
Keratinized
protection, and some
- Outer layer of the skin absorption
- Keratins reduce the loss of water
Transitional
from the body
- special type of stratified epithelium
Non keratinized
that can be greatly stretched.
- mouth is a moist nonkeratinized - Shape of the cells change as they
stratified squamous epithelium. stretch
- Protection against abrasion and act - lines cavities that can expand greatly,
as a mechanical barrier such as the urinary bladder.
- Water moves across it more easily - Protects underlying structure, like
than across the skin the urinary bladder
Free cell surface pass from one epithelial to an
adjacent one
- Most epithelia have a free surface
o Most epithelial cells are
that is not in contact with other cells
connected to one another by
and faces away from underlying
gap junctions
tissues.
o researchers believe that
- characteristics of the free surface
molecules or ions moving
reflect its functions.
through the gap junctions act
- smooth or lined with microvilli or
as communication signals to
cilia.
coordinate the activities of
- Cilia
the cells.
o Move materials over the top
of the cell
- Microvilli
o Increase surface are
Cell connection
- Functions of structure
o mechanically bind the cells
together,
o help form a permeability
barrier,
o and provide a mechanism for
intercellular
- Desmosomes
o Mechanical links that binds
cells together
- Hemidesmosomes
o Half desmosomes that
anchor cells to the basement
membrane Glands
- Tight junction
- secretory organs that secrete
o Prevent passage of materials
substances onto a surface, into a
between epithelial cells
cavity, or into the bloodstream
because they surround each
- composed primary of epithelium,
other
with a supporting network of
o Found in lining of the
connective tissues
intestines
- exocrine gland
- Gap junctions
o glands with ducts
o Small channels that allow
o multicellular or mostly
small molecules and ions to
composed of many cells
 ▪ classified according to Exocrine glands can also be classified
the structure of their according to how products leave the cell.
ducts and secretory
- Merocrine
gland
o secretion involves the release
o some exocrine glands are
of secretory products by
composed of single cell like:
exocytosis.
▪ goblet cell
- Apocrine secretion
• secret mucus
o involves the release of
- both glands and ducts are lined with
secretory products as
epithelium
pinched-off fragments of the
- endocrine gland
gland cells.
o ductless gland
- Holocrine secretion
o secret their products into the
o involves the shedding of
bloodstream
entire cells.
- simple gland
o have a single, non-branched
duct, some have branched
ducts
- Compound exocrine gland
o Multiple, branched ducts
o Tubular
▪ Secretory regions
shaped as small
tubules
o Acinar or alveolar
▪ Saclike structure
- Tubularianar or tubuloalveolar Connective tissue
o Both small shape tubules and
- diverse primary tissue type that
saclike structure
makes up part of every organ in the
body.
- Different from the other 3 tissue
because of abundant extracellular
matrix.
- comprised of cells, protein fibers,
and an extracellular matrix.
- Functions
o Enclose and separate other
tissues
o Connecting tissues to one
another
 o Supporting and moving parts o Fluid
of the body - Ground substance
o Storing compounds o Non-fibrous protein
o Cushioning and insulating - structure of the matrix is responsible
o Transporting for the functional characteristics of
o Protecting connective tissues
- Specialized cells that produce o for example, they enable
extracellular matrix bones and cartilage to bear
- Name of cell depending on their weight.
function
Matrix protein fibers
o Osteoblast
▪ Bone - 3 types
▪ Osteocytes maintain it o Collagen fibers
▪ Osteoclasts break it ▪ resemble microscopic
o Fibroblast ropes
▪ From fibrous ▪ very flexible but
connective tissues resist stretching.
▪ Fibrocytes maintain it o Reticular fibers
o Chondroblasts ▪ Very fine, short
▪ Cartilage and collagen fibers
chondrocytes ▪ branch to form a
maintain it supporting network.
- Found in connective tissue are cells o Elastic fibers
associated with the immune system, ▪ ability to return to
such as white blood cells. their original shape
o Microphages after being stretched
▪ Large cells or compressed
▪ Capable of moving ▪ giving tissue an elastic
and ingesting foreign quality.
substances
Matrix ground substance
o Mast cells
▪ Nonmotile - Consists of non-fibrous molecules
▪ Release chemicals - Shapeless
such as histamine, - Consist of proteoglycans
that promote o large molecules that consist
inflammation of a protein core attached to
many long polysaccharides.
Extracellular matrix
- Proteoglycans
- 3 major components o trap large quantities of water
o Protein fibers between the polysaccharides
o Ground substance
 o allows them to return to their such as spleen and
original shape lymph nodes
▪ as well as in bone
types of connective tissues
marrow and the liver.
- 2 types of connective tissues
o Embryonic
o Adult connective tissue
- By eight weeks of development,
most of the embryonic connective
tissue has become specialized to
form the types of connective tissue
seen in adults.
- Loose connective tissue
- consists of relatively few protein
fibers that form a lacy network, with
numerous spaces filled with ground
substance and fluid
- Most common cell in loose
connective tissue are the fibroblast
o 3 types of loose connective
tissues
▪ Areolar
▪ Adipose
▪ Reticular
Types of connective tissue
o Areolar
▪ Consist of collagen Dense
fibers and few elastic
- has large number of protein fibers
fibers
that form thick bundles and fill
o Adipose
nearly all of the extracellular space.
▪ consists of adipocytes,
- 2 types of dense connective tisues
or fat cells
o Collagenous
▪ contain large amounts
▪ has an extracellular
of lipid for energy
matrix
storage
▪ consisting mostly of
▪ Adipose tissue pads
collagen fibers.
and protects parts of
▪ Dense regular
the body and acts as a
• Collagen fibers
thermal insulator.
oriented in the
o Reticular
same direction
▪ Forms the framework
of lymphatic tissue,
 • Ex. Tendons,
ligaments
Cartilage
▪ Dense irregular
• Collagen fibers - composed of chondrocytes
oriented in - located in spaces called lacunae
multiple within an extensive matrix.
directions - Collagen in the matrix gives cartilage
• Ex. Dermis of flexibility and strength.
the skin, organ - resilient because the proteoglycans
capsule of the matrix trap water.
- provides support, but if bent or
slightly compressed, it resumes its
original shape
- 3 types of cartilage
o Hyaline
o Fibrocartilage
o Elastic cartilage
- Hyaline
o most abundant
o functions
▪ covering the ends of
Elastic bones
- fibrocartilage
- abundant elastic fibers among its
o more collagen than does
collagen fibers.
hyaline cartilage
- allow the tissue to stretch and recoil.
o able to withstand
- Ex. dense elastic connective tissue in
compression and resist
the vocal cords
tearing or pulling
- A genetic condition called Marfan
o location
syndrome results from, in part the
▪ intervertebral disks
inability to properly maintain and
▪ Bones of the back
form elastic fibers.
▪ Knee
▪ Temporomandibular
 - Elastic cartilage - 2 types of bones
o contains elastic fibers in o Spongy bone
addition to collagen and ▪ has spaces between
proteoglycans trabeculae or plates,
o appear as coiled fibers among of bone
bundles of collagen fibers o Compound bone
o able to recoil to its original ▪ solid, with almost no
shape when bent space
o location
▪ external ear
▪ epiglottis
▪ auditory tube
containing elastic
cartilage

Blood
- liquid connective tissue
- contains liquid matrix, termed
plasma, along with formed elements
- formed elements
o erythrocytes
o leukocytes
o platelets
- functions
Bone o transportation of food,
oxygen, waste, hormones,
- hard connective tissue that consists
and other substances
of living cells and a mineralized
matrix.
- Osteocytes are located within
lacunae.
- strength and rigidity of the
mineralized matrix enables bones to
support and protect
Muscle
- function o Smooth
o contract ▪ location
▪ contractile proteins • forms the
located within the walls of hollow
muscle cells organs
o shorten • skin
o movement • eye
- 3 type of muscle tissue ▪ function
o Skeletal • moving food
▪ Attached to the through the
skeleton to enable digestive tract
movement and emptying
▪ Striated or bonded. the urinary
bladder
▪ they are trapped at
each end, have a
single nucleus, and
are not striated

o Cardiac
▪ Heart
▪ Responsible for
pumping
▪ cylindrical but much
shorter than skeletal Nervous tissue
muscle cells - location
▪ striated and usually o brain
have one nucleus per o spinal cord
cell o nerves
▪ - function
▪ branched and o coordination
connected to one o control of body activities
another by o conducting action potential
intercalated disks. - consist of glial cells
o neurons and support cells
 - composed of 3 parts exterior of the body,
o cell body such as the
o dendrites pericardial, pleural,
o axon and peritoneal
cavities
▪ consist of 3
components
• simple
squamous
epithelium
• basement
membrane
Tissue membrane • loose
connective
- is a thin sheet or layer of tissue that tissue.
covers a structure or lines a cavity. ▪ do not contain glands
- Most membranes consist of ▪ secrete a small
epithelium and the connective tissue amount of fluid called
on which the epithelium rests serous fluid, which
- 4 types of tissue membranes lubricates the surface
o Cutaneous of the membranes
▪ External body surface o Synovial
membrane ▪ line the cavities of
▪ skin freely movable joints
o Mucous ▪ made up of only
▪ Consist of epithelial connective tissue
cells,their basement ▪ consist of modified
membrane, and a connective tissue cells
thick layer of loose ▪ produce synovial
connective tissue fluid, which makes the
▪ Mucous membrane joint very slippery
secretes mucus but ▪ function
not all • reducing
▪ Function friction and
• Protection allowing
• Absorption smooth
• secretion movement
o Serous within the
▪ line cavities that do joint
not open to the
 tissue repair
- substitution of dead cells for viable
cells
- occur by regeneration or by fibrosis
- regeneration
o new cells are the same type
as those that were destroyed,
and normal function is usually
restored
o can completely repair some
tissues, such as skin and the
mucous membrane of the
intestine
Tissue inflammation o accomplished by primary
stem cell
- beneficial when tissues are damage - fibrosis or replacement
- When viruses infect epithelial cells of o new type of tissue develops
the upper respiratory tract, that eventually causes scar
inflammation and the symptoms of production and the loss of
the common cold are produced some tissue function
- Inflammation occurs in stages - stem cells
- mobilizes the body’s defenses and o self-renewing
isolates and destroys o undifferentiated cells that
microorganisms and damaged cells continue to divide
so that tissue repair can proceed throughout life
- five major symptoms - Tissue repair occurs in sequential
o redness steps.
o heat
o swelling
o pain
o disturbance of function