Download Epithelial tissue (Epithelium)

Histology lecture I
Epithelial tissue
(Epithelium)
Prepared by
Dr. Mohamed Abdalla Eltayeb
College of medicine
Taibah University
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1.Epithelial tissue (epithelium)
 Epithelial tissue is one of the 4 basic
tissues of the body.
 Epithelial tissue exists in two forms:1. EPITHELIAL MEMBRANES
2. EPITHELIAL GLANDS
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Epithelial membranes (epithelium)
 Epithelial membranes are continuous
sheets of cells in contact with air (e.g.
skin and respiratory system) or with fluid
(e.g. stomach and urinary bladder).
 The cells of the epithelial membrane are
attached together by cell junctions
 Epithelial membranes are avascular.
They receive nutrition from blood capillaries
present in the undrlying connective
tissue.
Dr. Mohamed Abdalla Eltayeb
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Basal lamina and basement
membrane
 Epithelial cells secrete a glycoprotein layer
called basal lamina which separates them
from the connective tissue.
 The basal lamina is seen only with the
electron microscope (EM) and is not visible
with the light microscope.
 The connective tissue close to the basal
lamina is called basement membrane seen
with the light microscope (LM).
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Dr. Mohamed Abdalla Eltayeb
Classification of epithelial membranes
 According to the number of cell layers:1. Simple:- single layer of epithelial cells.
2. Stratified:- more than one layer of cells.
3. Pseudostratified:- single layer of tall &
short cells.
Dr. Mohamed Abdalla Eltayeb
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Classification of simple epithelium
 According to shape of cells in histological
sections:1. Simple squamous epithelium: single layer
of flattened cells e.g. peritoneum.
2. Simple cuboidal epithelium:- single layer
of squared cells e.g. kidney.
3. Simple columnar epithelium:- single
layer of rectangular cells e.g. stomach.
4. Simple columnar epithelium with goblet
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cells e.g. small intestine
Dr. Mohamed Abdalla Eltayeb
Simple squamous epithelium
Location:•
•
•
•
Blood vessels (Called endothelium)
Body cavities (Called mesothelium)
Kidney
Lung
Function:- Diffusion, Secretion, Transport
Single layer of squamous
cells with flat nuclei
Connective tissue
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Dr. Mohamed Abdalla Eltayeb
Simple cuboidal epithelium
Single layer of cuboidal cells(squares) with round
nuclei
Location: Thyroid gland
 Ducts in the kidney
 Ducts of exocrine glands
Function:-
Secretion and absorption
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Dr. Mohamed Abdalla Eltayeb
Simple columnar epithelium
Single layer of columnar cells (rectangular)
with oval nuclei
Basement membrane
Connective tissue
Location:- Stomach and gall bladder
Function:- Secretion and absorption
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Dr. Mohamed Abdalla Eltayeb
Goblet cell
 A goblet cell is a unicellular gland which
synthesizes and secretes mucin.
 Mucin is stored in the cytoplasm until it is
secreted and changed to mucus on the
surface of the epithelium.
 Mucus protects against foreign material
 Goblet cells are found in the epithelium of
the intestine and upper repiratory tract
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Dr. Mohamed Abdalla Eltayeb
Simple columnar epithelium with
goblet cells
Nuclei of columnar cells
Goblet cells
Basement membrane
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Nucleus of goblet cell
Stratified epithelium
 Stratified epithelium consists of 2 or
more layers of epithelial cells.
 According to the shape of cells of the
surface layer there are 3 types of stratified
epithelia:-
1. Stratified squamous epithelium
2. Stratified columnar epithelium
3. Transitional epithelium
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1. Stratified squamous epithelium
 The surface layer consists of squamous
cells. It is a protective epithelium.
 There are two types of stratified
squamous epithelium:2. Stratified squamous keratinized
epithelium : the cells of the surface layer
are dead cells consisting of keratin which is
a type of protein e.g. skin
1. Stratified squamous non-keratinized
epithelium: the cells of the surface layer
are nucleated living cells and do not form
keratin e.g. oesophagus
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Dr. Mohamed Abdalla Eltayeb
Surface layer of keratin without nucleated cells
Stratified squamous keratinized epithelium
Basement membrane
Connective tissue
Location:Skin
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Dr. Mohamed Abdalla Eltayeb
The rest of this lecture
is uploaded as
“Histology lecture II”
Dr. Mohamed Abdalla Eltayeb
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