Epithelial tissue
Dr. Amam Ali Amam
PhD: Periodontal Disease
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The human body is composed of only
4 basic types of tissue
Epithelial
tissue
Connective
tissue
Muscular
tissue
Nervous
tissue
They are formed by:
Molecules
Cells
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of the extracellular matrix
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The main characteristics of these basic types
of tissue:
tissue
Cells
Extracellular
matrix
Main
Function
Nervous
Intertwining
None
elongated processes
Transmission of
nervous impulses
Epithelial
Aggregated
polyhedral cells
Very small amount
Lining of surface or
body cavities,
glandular secretion
Muscle
Elongated
contractile cells
Moderate amount
Movement
Connective
Several types of
Abundant amount
fixed and
wandering cellsDr.AMAM. AMAM.
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Support and
protection
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Connective Tissue
is characterized by:
The abundance of extracellular
material produced by its cells.
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Muscular Tissue
is composed of:
elongated cells that have the
Specialized function of contraction .
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Nervous Tissue
is composed of:
cells with elongated processes
that receive, generate and
transmit nerve impulses
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Epithelial Tissues
are composed of:
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closely aggregated
very little
Polyhedral Cells
Extracellular Substance
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Epithelial tissue:
These tissues exist not as isolated units but
is association with one another and in variable
proportions, forming different organs & systems
of the body.
Epithelial cells covers or line surfaces
of the body & cavities
(eg, skin, stomach, oral cavity, all tubes inside the blood vessels).
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The principal Functions of Epithelial tissues are:
1- Covering & lining of surfaces (eg, skin, intestines).
2- Absorption (eg, intestines).
3- Secretion (eg, glands).
4- Sensation (eg, gustative & olfactory neuroepithelium)
5- Contractility (eg, myoepithelial cells)
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Epithelial Cells are covering & lining surfaces
and cavities of the body (external & internal surfaces).
Therefore, everything that enter or leave the body
should cross the epithelial sheet.
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Relationship between Epithelial Cells (E.C).
It’s very strong (firm), they should be continuous
Because they are going to ( cover, protect, make the function)
as perfect as possible.
They communicate because they want to know the
function of the other, and to live ( if one cell is underworking
then the other cell should raise up their level to cover for it )
or if it died.
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Most organs can be divided into 2 components
1- Parenchyma
2- Stroma
It’s the supporting
It’s composed of the
tissue, it’s made of
cells responsible for
connective tissue,
the main functions
except in the brain
typical of the organ
and spinal cord
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Forms of Nucleus & it’s location
Epithelial Cell nuclei have distinctive shapes:
Epithelial Cell
Nucleus shapes
Location
Cuboidal
Squamous
Spherical
Flattened
Central
Central
Columnar
Oval
near the
Basal
The long axis of the nucleus is always parallel
to the main axis of the cell.
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Specialization of the cell surface
1- Microvilli.
2- Cilia.
3- Flagella.
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1- Microvilli
They are found mainly on:
1- the Free cell surface.
2- absorptive cells (lining epithelium of the small intestines
& the cells of the proximal renal tubule).
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Microvilli
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2- Cilia
They are cylindrical motile
structures on the surface
of some epithelium cells.
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2 Types of Epithelium
according to structure & function
2- Glandular
Epithelium
1- Covering
Epithelium
1-Simple
1-Squamous.
2-Cuboidal.
3-Columnar.
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2-Stratified
3- Pseudostratified
1-Squamous keratinized.
2-Squamous non-keratinized
3-Cuboidal.
4-Transitional.
5-Columnar.
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Types of covering epithelium
1-Simple
2-Stratified
3- Pseudostratified
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Types of covering epithelium
Simple Epithelium Patterns
1-Squamous.
2-Cuboidal.
3-Columnar.
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1- Simple Squamous Epithelium
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1 Simple Squamous Epithelium
1Where it’s Located ?
lungs (alveoli).
capillary (endothelium).
lining of pleural cavity, the
pericardium, and the peritoneum.
Bowman's capsule (Kidney).
Blood vessels (endothelium).
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Simple Squamous Epithelium
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Simple Squamous Epithelium
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Simple Squamous Epithelium
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Columnar Simple Epithelium
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2-Simple Cuboidal Epithelium.
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2- Simple Cuboidal Epithelium
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2 Simple Cuboidal Epithelium
2Where it’s Located ?
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follicle of thyroid gland
collecting ducts of kidney
salivary glands.
Pancreas.
Ovary.
Uterus.
Lining of intestine.
gallbladder
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Cuboidal Simple Epithelium
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Cuboidal Simple Epithelium
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Cuboidal Simple Epithelium
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Cuboidal Simple Epithelium
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Types of covering epithelium
3-Simple Columnar Epithelium.
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3- Simple Columnar Epithelium
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3 Simple Columnar Epithelium
3Where it’s Located ?
Gallbladder.
surface epithelium of stomach.
Uterine glands (all phases).
small intestine
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Types of covering epithelium
Type
Cell
Form
Examples of
Distribution
Squamous Lining of vessels
(endothelium).
lining of cavities;
pericardium, pleura,
peritoneum
(mesothelium)
Simple
Cuboidal
Covering the ovary,
thyroid.
Columnar Lining of intestine,
gallbladder.
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Main Function
Facilitates the movement of
the viscera (mesothelium),
active transport by pinocytosis
(mesothelium & endothelium),
secretion of biologically active
molecules (mesothelium)
Covering, secretion.
Protection, lubrication,
absorption, secretion.
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Classification
Number of cell layers
simple
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stratified
Shape of the component cells
squamous
cuboidal
columnar
Presence of surface specialisations
keratin microvilli cilia
stereocilia
Glandular epithelia
exocrine
exo & endo
endocrine
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Types of covering epithelium
1-Simple
2-Stratified
3- Pseudostratified
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Types of covering epithelium
Stratified Epithelium Patterns
1-Squamous keratinized.
2-Squamous non-keratinized
3-Cuboidal.
4- Transitional.
5-Columnar.
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Stratified Squamous keratinized Epithelium
• specialised form of stratified squamous
epithelium ( epithelial surface of the skin )
epidermis
• is adapted to withstand the constant
abrasion , and desiccation
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Stratified Squamous keratinized Epithelium
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Stratified Squamous keratinized Epithelium
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Squamous keratinized
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Squamous keratinized
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Squamous keratinized
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Squamous keratinized
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Stratified Squamous non-keratinized
non keratinized (moist)
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Squamous Non-keratinized
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Squamous Non-keratinized
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Squamous Non-keratinized
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Squamous Stratified Epithelium
• consist of a variable number of cells layers
:
• cuboidal basal layer
• flattened surface layer
• is well adapted to withstand abrasion , and
is poorly adapted to withstand desiccation
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Squamous Stratified Epithelium
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Stratified Squamous non-keratinized
non keratinized (moist)
Where it’s Located ?
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oral mucosa
pharynx
esophagus
anal canal
uterine cervix & vagina
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Squamous Stratified Epithelium
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Transitional Stratified Epithelium
Where it’s Located ?
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Bladder, Ureters, renal calyces.
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Transitional Stratified Epithelium
• form of stratified epithelium
• urinary tract in mammals
• highly specialised : a great degree of stretch
to withstand the toxicity of urine
• it has some features which are intermediate
between stratified cuboidal and stratified
squamous epithelia
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Transitional Stratified Epithelium
• in the relaxed state : 4 – 5 cell layers
• basal cells are cuboidal.
• intermediate cells are polygonal.
• surface cells are large and rounded .
• in the stretched state : 2 – 3 cell layers .
•basal cells are cuboidal .
• intermediate and surface cells are flattened
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Transitional Stratified Epithelium
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Transitional Stratified Epithelium
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Transitional Stratified Epithelium
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Cuboidal Stratified Epithelium
Where it’s Located ?
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Ducts of sweat glands,
developing ovarian follicles.
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Cuboidal Epithelium
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Cuboidal Stratified Epithelium
• only two or three layers
• not involved in significant absorptive or
secretory activity but provides a more robust
lining than would be afforded by a simple
epithelium
• lining of the larger secretory ducts of exocrine
glands
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Types of covering epithelium
Type
Cell Form
Examples of
Distribution
Surface layer squamous
keratinized (dry).
Epidermis.
Protection ; prevents
water loss.
Mouth,esophagus,
larynx, vagina,
anal canal
Protection, secretion;
prevents water loss.
Cuboidal
Sweat glands,
developing
ovarian follicles.
Protection, secretion.
Transitional: domelike to
flattened, depending on
the organ.
Bladder, Ureters,
renal calyces.
Protection,
distensibility.
Columnar.
Conjunctiva.
Protection.
Surface layer squamous
Stratified nonkeratinized (moist).
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Main Function
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Ciliated Pseudostratified Epithelium
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Maxillary Sinus
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Pseudostratified columnar Epithelium
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Trachea
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Pseudostratified Epithelium
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Pseudostratified Epithelium
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Pseudostratified Epithelium
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Pseudostratified Epithelium
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Common types of covering epithelia in the human body
Type
Simple
Pseudostratified
Stratified
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Cell Form
Examples of
Distribution
Main Function
Squamous
Lining of vessels (endothelium).
Serous lining of cavities; pericardium,
pleura, peritoneum (mesothelium)
Facilitates the movement of the
viscera (mesothelium), active
transport by pinocytosis
(mesothelium & endothelium),
secretion of biologically active
molecules (mesothelium)
Cuboidal
Covering the ovary, thyroid.
Covering, secretion.
Columnar
Lining of intestine, gallbladder.
Protection, lubrication,
absorption, secretion.
Some columnar
& some cuboidal.
Lining of trachea, bronchi, nasal cavity.
Protection, secretion; ciliamediated transport of particles
trapped in mucus.
Surface layer squamous
keratinized (dry).
Epidermis.
Protection ; prevents water loss.
Surface layer squamous
nonkeratinized (moist).
Mouth, esophagus, larynx, vagina,
anal canal
Protection, secretion; prevents
water loss.
Cuboidal
Sweat glands, developing ovarian
follicles.
Protection, secretion.
Transitional: domelike to
flattened, depending on
the organ.
Bladder, Ureters, renal calyces.
Protection, distensibility.
Columnar.
Conjunctiva.
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Dr.AMAM. AMAM.
Protection.
Glandular Epithelium
1.
2.
3.
Glandular epithelial cells (store &
secrete :
proteins (eg: pancreas)
lipids, ( eg: sebaceous glands)
carbohydrates and proteins,
(eg: salivary glands)
•
•
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Mammary glands do all that.
Secretes substances from the blood,
sweat glands
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Types of glands
1.
2.
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Unicellular: goblet glands.
Multicellular:
Exocrine
Endocrine
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Glandular Epithelium
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Glandular Epithelium, Exocrine glands
The morphology of the gland
Simple glands
• single, unbranched duct, secretory portions.
tubular or acinar , coiled or branched.
Compound glands
• branched duct system
secretory portions have similar morphological
forms to those of simple glands
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The means of discharge of secretory form the cells
‫فارزة‬
• Merocrine secretion ( eccrine ) - salivary glands
َ ‫ ُم ْف َت‬Apocrine secretion - breast , sweat glands
• ‫رزة‬
• ‫ ُم ْن َف ِر َزة‬Holocrine secretion - sebaceous glands
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Stomach
Several tubular secretory portions, single unbranched
duct , is lined by mucus-secreting cells. No goblet cells
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Simple acinar glands
Mucus-secreting glands / Penilee urethra
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Sebaceous glands
Several secretory acini , single
excretory duct - stratified e.
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Brunner’s glands / duodenum
Duct is branched, tubularDr.AMAM.
branched
coiled secretory portions٨٨
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Pancreas
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Submandibular salivary gland
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Endocrine glands
• ductless
• secretory products – HORMONES
• rich network of small blood vessels
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