This document provides information on epithelial tissue. It begins by defining epithelium as sheets of cells that cover outer surfaces of the body and line internal organs. Epithelial tissue is classified based on the number of cell layers and cell shapes. There are simple, stratified, pseudostratified and transitional epithelia. The document also describes basement membranes, intercellular junctions, and specializations of the free cell surface like microvilli, cilia and stereocilia. Glandular epithelia are discussed, including exocrine and endocrine glands and their classifications.

1. EPITHELIAL TISSUE
DR. DEVI5/28/2019 1

2. CONTENTS
EPITHELIAL TISSUE
CHARACTERISTIC FEATURES
CL ASSIFICATION
BASEMENT MEMBRANE
INTERCELLUL AR CONTACTS
SPECIALIZATION OF FREE
SURFACE OF CELL
GL ANDUL AR EPITHELIA
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3. EPITHELIUM
• Basic tissue of the body
• Cells arranged as continuous sheets
• Single or multiple layers
• Covers the outer surface of the body or line the
luminal surface of tubular structures and cavities of
the body
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4. • Cell junctions
• Basement membrane : thin , continuous supporting
layer , basal lamina
• Epithelioid tissues
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5. CHARACTERISTICS OF EPITHELIAL
TISSUE
• Epithelium consists of tightly packed cells- very
cellular with little intercellular space 20um
• Usually avascular- They lack a blood supply, instead
they receive nutrients by diffusion from capillaries in ct
• Epithelium readily divide, so they are continually
replaced = rapid healing- high capability to regenerate
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6. • Cells rest on basement membrane
• Cells shows polarity
• Cells may display surface
modification
• Supplied by nerves
• Secretory portion of glands and
cells lining the ducts are epithelial
in nature (glands are epithelial in
origin)5/28/2019 6

7. FUNCTIONS
• Protection - skin , body cavities
• Absorption – kidney, intestine
• Secretion – gastric, intestinal glands
• Exchange – renal tubules
• Barrier- skin, urinary bladder
• Excretion – nephron of kidney
• Combine with nervous tissue- special organs
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8. CLASSIFICATION
1. Simple (squamous / cuboidal / columnar)
2. Stratified (St. squamous / St. cuboidal / St. columnar)
3. Pseudostratified
4. Transitional
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Shape/arrangement/specialization of their free
surface
Keratinized/ non-
keratinized

9. SIMPLE EPITHELIUM
• Unilayered
• Single layer of cells resting on basement membrane
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10. 1.squamous = scale-like
2.cuboidal = cube-like shape
3.Columnar = tall cells
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11. SIMPLE
SQUAMOUS
• Single layer of flattened cells
• Functions include diffusion,
filtration, and secretion
 Locations include:
• air sacs of lungs (alveoli)
• lining of capillaries and the walls
of blood vessels, glomerulus of
kidneys, endocardium, internal
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12. S I M P L E
S Q UA M O U S
• Polygonal outlines
• Height less as compared with
width
• Thin layer
• Nucleus –oval/flat, Nuclei
forms bulging of cell surface
• Endothelium
• Mesothelium
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13. 5/28/2019 13

14. SIMPLE CUBOIDAL EPITHELIUM
• Height is same as that
of width
• Round nuclei
• Sectional view-
cuboidal in shape
• Surface view-
hexagonal in shape
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15. SIMPLE
CUBOIDAL
• Single layer of cube-shaped
cells
• Functions include secretion
and absorption
• Locations include
• Follicles of thyroid
• the lining and the ducts of
some glands
• Surface of ovary
• tubules within kidneys
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16. SIMPLE
COLUMNAR• Cells –taller
• Elongated nuclei-located at the
lower half
• All nuclei at same level
• Vertical section- rectangular ,
surface view- polygonal
• Cilia/ microvilli
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17. SIMPLE
COLUMNAR• Location: stomach & large
intestine, Brush border- gall
bladder, ciliated columnar
epithelium-respiratory tract,
uterus, central canal of spinal
cord, ventricles of brain
• Function: secretion, absorption
Goblet cells
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18. STRATIFIED EPITHELIUM
STRATIFIED SQUAMOUS
(NON-KERATINIZED)
• Many layers
• Basal layer-
cuboidal/round,
intermediate- polyhedral,
superficial layer- flattened
• Location- lining oral cavity,
tongue, part of epiglottis,
oesophagus , vagina
• Function- protection of
STRATIFIED SQUAMOUS
(KERATINIZED)
• Dead, dehydrated, non-
nucleated like scales
• Location- skin
• Function- protection,
prevents absorption of
water, prevents
dehydration of underlying
tissues
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19. KERATINIZED STRATIFIED SQUAMOUS
EPITHELIUM OF EPIDERMIS
NON KERATINIZED STRATIFIED
SQUAMOUS EPITHELIUM
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20. 5/28/2019 20

21. STRATIFIED CUBOIDAL
• Many layers
• Ducts of sweat glands
• Provides passage to the
secretion and act as a
barrier
STRATIFIED COLUMNAR
• Many layers
• Epithelium lining large
ducts of glands
• Fornix of conjunctiva,
urethra
• Provides passage to the
secretion and acts as
barrier
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22. PSEUDOSTRATIFIED EPITHELIUM
• Not a true stratified epithelium
• Appears to be stratified
• All cells are attached to the basement membrane but
are of different heights
• hence not all reach the apical surface
• Nuclei at different levels
• Ciliated/non-ciliated , goblet cells
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23. Location :
• Non- ciliated – auditory tube, ductus deferens, male urethra
• Ciliated –trachea & large bronchi
• Pseu stra col epi with sterocilia- epididymis
Function:
• Tall columnary- Secretory
• Short, basal cells are stem cells- replace tall cells
• Cilia help in clearance of mucous
• Stereocilia help in absorption
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24. • Pseudostratified ciliated
columnar epithelium lining the human trachea
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26. 5/28/2019 26

27. TRANSITIONAL EPITHELIUM
• Mutilayered 4-6 cells thick
• Differs from stratified squamous epithelium , surface
cells are not squamous
• Deepest cells- columnar/ cuboidal
• Middle layer-polyhedral/pear-shaped
• Surface layer- umbrella shaped
• Can be stretched without losing heir integrity-
becomes thinner and flattened
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28. • Location :
Renal pelvis, calyces, ureter, urinary bladder, part of
urethra
Urothelium
• Function :
The presence of occluding junctions and
intramembranous plaques forms an effective barrier,
prevents absorption of toxic substances of urine
Distention
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29. 5/28/2019 29

30. BASEMENT MEMBRANE
• thin supporting layer placed between basal surface of
epithelium and under line connective tissue
• Epithelium cells rest on the basement membrane
• Under EM – appears by layers , basal lamina and
reticular lamina
Functions: provides adhesion on one side to epithelial
cells , other side connective tissue ,
• Act as barrier of diffusion
• Influence regeneration of peripheral nerves
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31. INTERCELLULAR CONTACTS
• Zonula occludens ( tight junctions)
• Zonula adherens
• Desmosomes (macula adherens)
• Gap junction
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32. SPECIALIZATION OF THE FREE
SURFACE OF THE CELL
a. Microvilli
b. Stereocilia
c. Cilia
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33. Cilia :
• Hair like projections
• Free part of the each cilia- shaft
• Region of attachment of shaft to cell- base
• Outer covering- extension of cell membrane, inner
core- microtubules
• Functions : wave-like movements on the surface of
tracheal and bronchial epithelium help to move the
mucous in one direction , movement of ova in oviduct
•
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34. Micro villi:
• Fine vertical striations / finger like projections
• Closely packed
• 1-2 um , 75-90 um
• Plasma membrane/ cytoplasmic core/ microfilaments/
actin filaments
• Brush border
• Function : non-motile process, increase the surface
area, active absorption
• Location : intestine, proximal convoluted tubule of
kidney5/28/2019 34

35. Stereocilia:
• Long cytoplasmic
process, 5-10um
• Non motile
• Increase SA
• Location :lining
epithelium of
epididymis, sensory cells
of ear
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36. GLANDULAR
EPITHELIA
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37. • Glands – specialized secretory cells
• Epithelial in origin
• Unicellular or multicellular
• Exocrine glands : epithelial layer
invaginates in deeper tissue to
form a diverticulum. The proximal
end of this forms duct while distal
end forms secretory units. These
type of glands remain in contact
with surface epithelium by the
duct and pour their secretions on
its surface5/28/2019 37

38. • Endocrine glands: some glands
lose contact with the epithelial
surface. They pour their
secretions directly in the blood.
(internally secreting glands/
duct less glands)
• Paracrine : similar to endocrine,
but secretion diffuses directly
into target cells eg : bronchus
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39. EXOCRINE GLANDS
Classification
Branching ducts
• Simple gland – unbranched eg: gastric , sweat glands
• Compound gland – branched eg: parotid gland
Shape of the secretory unit
• Tubular- tubular shape eg; gastric glands
• Acinar- oval shape eg; salivary glands
• Alveolar- flask shaped eg: sebaceous glands
• Saccular – sac shaped eg: mammary glands
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40. Nature of secretion :
• Mucous
• Serous
• Mixed
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41. Simple glands
• Simple tubular- large intestine
• Simple alveolar – sebaceous gland
• Simple acinar-salivary gland
Compound glands
• Compound alveolar- pancreas, parotid
• Compound tubular- brunner’s gland
• Tubulo alveolar- salivary gland
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43. THANK YOU !
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