EPITHELIUM

By Dr. Jagdish S. Chaudhari

Assistant professor,

Department of Anatomy.

Histological organization �from cell to organ system

• Histology :-
• Cell :-
• Tissue :- 4 basic types
• Organ :-
• System :-

Four basic types of tissues

• EPI = UPON
• THELIA = NIPPLE LIKE

BASEMENT MEMBRANE

CELLS

Epithelium is a upward projection over basement membrane

Lamina propria

Epithelium :-

Outer surface of body & Luminal surface of cavity within

the body are lined by the cells arranged in the form of

continuous sheet in either single or multiple layer that

completely cover them, such layer of cell are called…..

What are Epithelioid tissue ?

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At certain places of the body , Cells are found aggregated

in close apposition with one another like epithelial tissue

but do not present a free surface, called ……

e.g. Leydig cells of testes , Luteal cell in ovary ,

Parenchyma of adrenal gland.

Epithelial tissue is AVASCULAR TISSUE.

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Epithelial tissue is supplied by NERVE.

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Constant Wear & Tear –High capability to regenerate

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Glands are epithelial in origin.

Function of Epithelium :-

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Protective :– Epithelium of Skin & Body Cavity.

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Absorptive :- Epithelium of kidney & intestine.

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As Barrier :- Epithelium of Skin & urinary bladder.

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Excretion :- Epithelium of certain part of nephron of kidney.

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Secretory :- Epithelium of intestine ,Goblet cell, Gastric & intestinal gland.

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Special organ of sense :- Hearing, Smell, Vision.

Epithelial tissue

Surface / lining epithelium

Glandular epithelium

Protection

absrption

myoepithelium

contraction

Neuro-epithelium

secretion

CLASSIFICATION OF Epithelial tissue

secretion

CLASSIFICATION OF surface / lining EPITHELIUM

SIMPLE SQUAMOUS ( pavement ) EPITHELIUM

SQUAMOUS = SCALE LIKE

diffusion

:Examples of SIMPLE SQUAMOUS (pavement) EPITHELIUM:

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• Endothelium :

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lining epithelium of Heart , blood vessels, & lymphatics.

:Examples of SIMPLE SQUAMOUS (pavement) EPITHELIUM:

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• Mesothelium:-

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lining epithelium of serous membrane of body cavity like, pleura , pericardium & peritoneum.

:Examples of SIMPLE SQUAMOUS (pavement) EPITHELIUM:

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3. Lining epithelium of alveolus of lungs:

Lining epithelium

:Examples of SIMPLE SQUAMOUS (pavement) EPITHELIUM:

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4. Lining epithelium of Loop of henle of renal tubules

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renal corpuscles. . . .

Loop of henle

Functions of SIMPLE SQUAMOUS EPITHELIUM :-

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1. Help in rapid transport of substance ,

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2. filtration of fluid ,

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3. diffusion of gases and osmosis.

SIMPLE CUBOIDAL ( cubical ) EPITHELIUM

CUBOIDAL

Secretion & Absorption

Hexagonal

: examples of SIMPLE CUBOIDAL ( cubical ) EPITHELIUM:

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• Follicles of thyroid gland.

Follicles of thyroid gland

Simple squamous epithelium when gland is

inactive stage

simple columnar epithelium when gland is

highly active stage

Simple Cuboidal epithelium

when gland is

average active stage

examples of SIMPLE CUBOIDAL( cubical ) EPITHELIUM:-

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• Germinal epithelium = lining epithelium of ovary

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• Choroid plexus

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• inner surface of lens

: examples of SIMPLE CUBOIDAL(cubical) EPITHELIUM:-

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• pigment layer of retina.

examples of SIMPLE CUBOIDAL(cubical) EPITHELIUM with brush border:-

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• Proximal convoluted tubules of kidneys

Proximal convoluted tubules

SIMPLE COLUMNAR EPITHELIUM.

COLUMNAR

Absorption

Secretion

transport

SIMPLE COLUMNAR EPITHELIUM

1. WITHOUT SURFACE SPECIALIZATION

2. CILIATED

3. GLANDULAR

4. WITH MICROVILLI

BRUSH BORDER/STRAITED BORDER

examples of SIMPLE columnar EPITHELIUM without surface specialization :-

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• Mucous membrane of stomach

examples of SIMPLE columnar EPITHELIUM without surface speicalization :-

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2. mucous membrane of large intestine

examples of SIMPLE columnar EPITHELIUM with striated border:-

3. mucous membrane of small intestine.

examples of SIMPLE columnar EPITHELIUM with brush border:

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• mucous membrane of gall bladder

Examples of ciliated columnar EPITHELIUM :-

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• Respiratory tract

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• Uterus

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• Uterine tube

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• Efferent ductules of testis

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• Auditory tube

examples of secretory columnar EPITHELIUM:-

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• Mucosa of stomach & intestines .

Goblet cells

Functions of SIMPLE COLUMNAR EPITHELIUM.

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• Acts as a protective barrier.

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• concerned with secretion , absorption

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• When cilliated - propulsion of mucus.

• SIMPLE EPITHELIUM = SINGLE LAYERED

SQUAMOUS

CUBOIDAL

COLUMNAR

STRATIFIED EPITHeLIUM = MULTI-LAYERED

SQUAMOUS

CUBOIDAL

COLUMNAR

TRANSITIONAL

• STRATIFIED squamous EPITHLIUM

keratinized

Non -keratinized

• STRATIFIED squamous Keratinized EPITHeLIUM .

Epidermis of skin .

• Protection of deeper

structure.

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• Prevent absorption of

water.

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• Keratin prevent

dehydration of

underlying tissue.

2. non-Keratinized STRATIFIED squamous EPITHeLIUM

it lines wet cavity ,subject to abrasion like; oral cavity, Tongue ,Pharynx.Part of epiglottis, Oesophagus, vegina, cornea.

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Function:- protection of deeper tissue.

Stratified cuboidal epithelium .

present in :-

duct of salivary gland

& sweat gland.

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Function :- limited absorption

& protection

Stratified columnar epithelium .

present in :-

fornix of conjuctiva &

cavernous urethra.

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Function :-

Provide passage to the

secretion And act as barrier.

pseudo-stratified columnar epithelium

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• May be ciliated or noncilited.
• May contain goblet cell.

Columnar epithelium

pseudo-stratified non ciliaed epithelium .

• Auditory tube.

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• Ductus deferens.

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• Male urethra . (membranous part & penile part).

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• Large excretory duct.

pseudo-stratified ciliaed epithelium .

• Upper respiratory tract.

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examples of pseudo-stratified ciliated columnar epithelium .

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• Trachea

Pseudo stratified ciliated columnar epithelium

Basal lamina

examples of psudo-stratified ciliated coulmnar epithelium .

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2. Large bronchi.

Transitional EPITHeLIUM = urothelium

Dome / umbrella shaped surface cell .

Transitional EPITHeLIUM = urothelium

Dome / umbrella shaped surface cell .

Transitional EPITHeLIUM= urothelium

PRESENT IN EPITHELIUM LINING THE URINARY TRACT.

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FUNCTION:-

• ACT AS A BARRIER ,
• TO PREVENT ABSORPTION OF TOXIC SUBSTANCE OF URINE.
• DISTENTION OF BLADDER.

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The Basement membrane.

Basal lamina.

Reticular lamina.

Not clearly seen in H & E,

but it seen well defined magenta colour in PAS .

Function of The Basement membrane.

• it provides support to the epithelium.

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• it provides selective filtrarion barrier.

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• It help epithelium to attached to underlying tissue.

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• It help in regeneration of peripheral nerves.

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• Basal lamina of glomerular capillaries are

thick in certain disease of kidney.

INTER CELLULAR CONTACTS.

FUNCTIONS OF TIGHT JUNCTION.

Act as barrier.

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Prevent passage of large & small molecule between cell.

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Prevent leaking of content of organ into blood / surrounding tissue.

Commonly seen in Kidney tubules , intestine , urinary - bladder.

ZONULA ADHERANCE.

FUNCTIONS :-

It provide strong adhesion between adjucent cell.

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It gives stability to the terminal web of the cell.

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Terminal web of the cell are interconnected.

DESMOSOMES / MECULA ADHERANCE.

FUNCTIONS :-

It present in epithelia that are subjected to abresion or physical stress , Epidermis.

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It gives stability to epithelium as a whole by linking cytoskeleton of adjucent cell.

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It provide strong adhesion between cells.

Gap junction ( Nexus)

FUNCTIONS :-

It coordinates the activity of cell in epithelium.

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It help nerve / muscle impulse to spread rapidly between cell.

Specialization of free surface of epithelial cell.

3. Surface projection over epithelial cells :-

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• Microvilli.

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• Cilia.

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• stereocilia.

Microvilli :- cytoplasmic finger like protrusion of

apical surface of cell …

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1-2 micrometer length, 80-90nm in dm.

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Regularly arranged microvilli –striated border (GIT )

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i rRegularly arranged microvilli –brush border

(Gall bladder , pct of kidney. )

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cilia :- short, fine, hair like structure arranged in raw on apical surface of cell…

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10 micrometer length, 0.3 micrometer in dm.

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Wave like movement - help to move mucous toward pharynx.

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Help in Movement of ova in oviduct.

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stereocilia :-

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Found on apical surface of the epithelium lining epididymis and on sensory cell of ear.

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stereocilia have long cytoplasmic process

5 - 10 micrometer length, large microvili.

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Lack of actin filament.

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Serve as absorptive device.

Thank you.

Pecularities of surface epithelium

4. epithelial cells contain pigment:-

• skin
• Retina
• Iris

Pecularities of surface epithelium

• Epithelia devoid of blood vessels except stria vascularis of cochlea.

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Pecularities of surface epithelium

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• Epithelial cells look alike have different function

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• Glandular epithelium

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• Epithelial cells contains proteins - cytokeratin

Fuctions of epithlium

• protection
• secretion
• absorption
• lubrication

Mucous membrane

Tumours arising from the epithelium

• carcinoma