Epithelial tissue
Mrs. Dalia Kamal Eldien
MSC in Microbiology
Lecture NO 2
Objectives
 To explain What is epithelium.
 What are the types of epithelium and their functions.
 What are the locations of different epithelium in human
body.
Introduction
oDespite its complexity, the human body is composed of
only four basic types of tissue: Epithelial tissue
 Connective tissue
Muscular tissue
 Nervous tissue
oThese tissues, which all contain cells and molecules of the
extracellular matrix (ECM), exist in association with one
another and in variable proportions and morphologies, forming
the different organs of the body.
Definition of Epithelium
Epithelium is a type of animal tissue made up of layers of
closely packed cells, with very little intercellular space.
Characteristic of epithelial
1) Covers the internal and external surfaces of body.
2) Forms the linings of body cavities and vessels.
3)
Have no blood supply (AVASCULAR)
4) Can easily regenerate if well nourished.
Functions
1) Covering, lining, and protecting surfaces (eg, skin)
2) Absorption (eg, the intestines)
3) Filtration (eg, the blood capillaries of kidney)
4) Secretion (eg, the epithelial cells of glands)
Basement membrane
Epithelial tissue rests on a basement membrane, a thin
delicate membrane of protein fibers and glycosaminoglycans
separating an epithelium from underlying tissue, which acts
as a scaffolding on which epithelium can grow and
regenerate after injuries
1) Basal lamina
2) Reticular lamina.
Basement membrane
1) Basal lamina:
The basal lamina is secreted by the epithelial cells.
Visible only with the electronic microscope
1) Reticular lamina:
Is secreted by fibroblasts located in the underlying
connective tissue.
Basement membrane
Functions of the Basement Membranes:
1) Provides support and attachment for the epithelial cells
2) Selective diffusion barrier
Classification of epithelial
Epithelium can be classified by:
1.Number of cell layers
2.Shape of uppermost cells
Classification of epithelia
Number of cell layers
One layer of cells
More than one layer
(Simple epithelium)
(Stratified epithelium)
Classification of epithelia
Simple epithelium:
1) One cell layer thick
2) All cells rest on the basement membrane
Stratified epithelium
1) More than one cell layer thick
2) Only the deepest layer of cells contact the basement
membrane
Classification of epithelia
SHAPE OF CELLS
FLAT
CUBE LIKE
COLUMN LIKE
(SQUAMOUS)
(CUBIODAL)
(COLUMNAR)
Epithelial cells
o There are three principal morphologies associated
with epithelial cells:
 Squamous epithelium has cells that are wider than
they are tall (flat and scale-like), Nucleus flat,
central.
 Cuboidal epithelium has cells whose height and
width are approximately the same (cube shaped),
Nucleus spherical .
 Columnar epithelium has cells taller than they are
wide (column-shaped), Nucleus oblong basal.
Epithelial cells
Naming the epithelial tissue
First name of tissue indicates number of cell
layers:
 Simple – one layer of cells
 Stratified – more than one layer of cells
Last name of tissue describes shape of cells
 Squamous
 Cuboidal
 Columnar
Types of epithelial
SIMPLE EPITHELIUM:
1. Simple squamous epithelium
is one cell thick; that is, every cell is in direct contact with
the underlying basement membrane. In general, it is
found where absorption and filtration occur. The thinness
of the epithelial barrier facilitates these processes
Simple squamous epithelium
Simple squamous epithelium
SIMPLE SQUAMOUS EPITHELIUM
• LOCATION
• Endothelium: heart, blood vessels, lymphatic.
• Mesothelium : Pericardium, pleura ,peritoneum.
• others：alveoli of the lungs, in kidney tubules etc
2.Simple cubiodal epithelium
These cells may have secretory, absorptive, or excretory
functions. examples include small collecting ducts of
kidney, pancreas and salivary gland.
Simple cubiodal epithelial
Simple cubiodal epithelial
Simple cubiodal epithelial
SIMPLE CUBIODAL EPITHELIUM
LOCATION
1. In most of glands like salivary, mammary etc
2. In collecting ducts of kidneys
Types of epithelial tissue
3.Simple columnar epithelium.
found in areas with extremely high secretive (as in
wall of the stomach), or high absorptive (as in small
intestine) areas. they possess cellular extensions
(e.g. microvilli in the small intestine, or cilia found
almost exclusively in the female reproductive tract).
Simple columnar epithelial
Simple columnar epithelial
Types of epithelial
SIMPLE COLUMNAR EPITHELIUM
LOCATION
Mostly located in the
lining of small
intestine
Types of epithelial
STARTIFIED EPITHELIUM
1. Stratified squamous epithelium
2. Stratified cuboidal epithelium
3. Stratified columnar epithelium
OTHER TYPES
1. Pseudo stratified columnar epithelium
2. Transitional epithelium
Types of epithelial
STRATIFIED SQUAMOUS EPITHELIUM
LOCATION
• outer layers of skin, linings of oral cavity, throat, vagina,
and anal canal
STRATIFIED SQUAMOUS
EPITHELIUM
STRATIFIED SQUAMOUS
EPITHELIUM
Types of epithelial cells
STRATIFIED CUBIODAL EPITHELIUM
LOCATION
Mostly located in the ducts of salivary , sweat and
mammary glands
STRATIFIED CUBIODAL
EPITHELIUM
STRATIFIED CUBIODAL
EPITHELIUM
Types of epithelial
Stratified columnar epithelium
LOCATION
Located in male urethra
Stratified columnar epithelium
Stratified columnar epithelium
Types of epithelial cells
PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
Pseudo means (false)
1. Appears stratified because nuclei are at 2 or more levels
2. NOT stratified because all cells touch basement
membrane.
It can be ciliated or non ciliated.
LOCATION
oNon ciliated variety is located in the ducts of male
reproductive system
oCiliated type is located in upper respiratory tract eg trachea.
PSEUDOSTRATIFIED COLUMNAR
EPITHELIUM
\PSEUDOSTRATIFIED COLUMNAR
EPITHELIUM
CILIATED PSEUDOSTRATIFIED
COLUMNAR EPITHELIUM
Types of epithelial cells
TRANSITIONAL EPITHELIUM
The transitional epithelium is named so because it can
transit between two states.
1. In empty bladder cells are umbrella shaped and show
many layers.
2. In full bladder cells become flattened and show less
layers.
LOCATION
Located in the inner lining of urinary bladder
Types of epithelial cells
TRANSITIONAL EPITHELIUM
Classification of epithelial
tissue
Home work
Describe the following
• Squamous, Cuboidal and columnar
epithelium cells ???????
• Write shortly on the classification of
epithelial cells ???????
Why the transitional epithelium named so
?????????