hanan jaafer - ju medicine2 | p a g e • epithelium is an avascular “a means no “ → there...
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1 | P a g e
Jehad Samhouri
Dana Ziyad Almanzalji and ru'aa Nade
Hanan Jaafer
4
2 | P a g e
• Epithelium is an avascular “a means no “ → there aren’t any blood
vessels inside epithelium tissues.
So , how do they get food and Oxygen?
By connective tissue that located under epithelium tissues.
Epithelial tissue composed of cells ( packed together ) that cover the
exterior body surfaces and line internal closed cavities and tubes with
little intercellular material .
“No space between them, so it doesn’t have vascular”.
1. It forms the secretory portion of glands and their ducts. “Ducks are
coming out from glands ’’.
2. Specialized epithelial cells function as receptors for the special senses.
3. Covering the exterior body surface and lining the internal closed cavities.
• Epithelial cells are polarized ( different domains with different function )
and resting on basement membrane.
Can be derived from all embryonic germ layers:
( ectoderm , mesoderm , endoderm )
• Epithelium lining skin, mouth, nose and anus: ectoderm “most external
layer’’
• Epithelium lining respiratory system, digestive tract and glands of
digestive tract: endoderm “most internal layer”
• Epithelium lining blood vessels: mesoderm
Epithelial tissue could be found in :
General features:
Note:
The Epithelium that lines blood vessels are called Endothelium which is
derived from mesoderm.
3 | P a g e
• We all came from Zygot , then it will divide then it will differentiate into
different kind of cells .
• Cells at day 16 , will arrange in 3 layers are called Germ Layer .
• Every layer has its own derivations .
• Epithelium can be deviated from any layers depending on its final
destination .
Cell Polarity :
Note : Apical surface always towards space
either Lumen or External Enviroment .
4 | P a g e
The epithial cell shows two domains
1) Apical
2) Baso-lateral
➢ Each domain shows modifications to suit its functions
Function : • Protection
• Transcellular transport
• Secretion
• Absorption (selective permeability)
• Involved in sensation
According to number of layers
Simple : one layer of cells are resting over the Basal Lamina
Classifications & Naming of Epithelia :
5 | P a g e
Stratified : more than one layer of cells “ multiple layers of cells”
According to shape of cells
o Squamous : cells wider than tall (plate or
“scale” like)
o Cuboidal : cells are as wide as tall, as in cubes
o Columnar : cells are taller than they are wide,
like columns
Naming Epithelia
• Naming the epithelia includes both the layers (first) and the
shape of the cells (second)
I.e. stratified cuboidal epithelium
• The name may also include any accessory structures:
o Keratin” water resistance “
o Goblet cells “secreted mucus “
o Cilia
Note : not all the Basal Surfaces reaching the Basal
Lamina only the most basal is reaching the Basal
Lamina .
6 | P a g e
➢ Special epithelial tissues (don’t follow naming convention)
o Pseudostratified
o Transitional
Epithelium
Simple
Squamous
Cuboidal
Columnar
Pseudostratifie
d
Stratified
Squamous
keratiniz
ed
nonkeratinize
dCuboid
al
Transitional
Columnar
7 | P a g e
Simple Epithelium
Simple Squamous Epithelium Simple Cuboidal Epithelium
Ciliated Simple Columnar Epithelium
Note : This name for the right side
8 | P a g e
Ciliated Pseudostratified
columnar Epithelium with Goblet
Cells. “Respiratory Tissue “
Stratified Epithelium
Stratified Squamous Stratified Cuboidal
Notice that its neither Keratinized always 2 layers
nor nonkeratinized
Note : all cells are resting on Basal Lamina
even though some cells are short and
can’t reach the Apical Tissue
9 | P a g e
Stratified Columnar Transitional Epithelium
In this case we name This type of tissue is found
Depending on which in Urinary Bladder
Cell is nearer to Apical
Surface
Simple Squamous
Locations:
o Vascular system (endothelium)
o Body cavities (mesothelium)
o Bowman’s capsule (kidney)
Major function:
o Exchange
Simple Epithelia :
10 | P a g e
Endothelium is the simple
squamous epithelium that
lines the lumen of the
cardiovascular system
Mesothelium is the simple
squamous epithelium that
lines serous cavities
(peritoneal “abdomen’’,
pleural ”lung” , and
pericardial cavities
“around heart’’) and coats
many of the organs in
these cavities
• Contain two or more layers of cells
• Regenerate from below
• Major role is protection
• Are named according to the shape of cells at apical layer
• Mitotic activity in stratified epithelium is limited to the basal
layer (under normal conditions)
• If cells in Apical die , the cell in Basal must divide in order to
regenerate them.
Stratified Epithelia
11 | P a g e
❖ Stratified Squamous Epithelium
➢ Specific types
❖ Keratinized : contain the protective protein keratin
(keratin is water resistance protein and we need it in our skin )
→ Surface cells are dead and full of keratin
❖ Non-keratinized : forms moist lining of body openings
➢ Function
Protects underlying tissues in areas subject to abrasion
➢ Location
Keratinized : forms epidermis
Non-keratinized : forms lining of mouth, esophagus, and vagina
Nonkeratinized Stratified Squamous Keratinized Stratified Squamous
Note: the upper layer is sac full of
keratin
12 | P a g e
Goblet cells produce mucus
Cilia (larger than microvilli) sweep mucus
Ciliated Pseudostratified Columnar
Epithelium with goblet cells
{ وإن يُردك بخيٍر فال راد لفضله }
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