1. EPITHELIUM
CAPT DR POONAM SINGH
DEPT OF ANATOMY

2. SEQUENCE OF PPT
1.
2.
3.
4.
5.
6.
7.
8.
INTRODUCTION
DEVELOPMENT
CLASSIFICATION
HISTOLOGICAL APPEARANCE
APICAL DOMAIN & ITS MODIFICATIONS
LATERAL DOMAIN & ITS SPECIALIZATIONS
BASAL DOMAIN
GLANDS & ITS TYPES

3. TISSUES
4 Basic types

4. DEVELOPMENT

5. 5 – 6 DAY

6. 6th DAY
Implantation of the Blastocyst

7. 9TH DAY

9. DEVELOPMENT

10. DEVELOPMENT OF EPITHELIUM
1. Ectoderm:- skin, hair follicles, mammary glands,
cornea, conjunctiva, some parts of mouth & anal
canal.
2. Endoderm:- GIT ( except part of mouth &anal canal),
resp tract, glands.
3. Mesoderm:-body cavities (Mesothelium),
endothelium.

11. EPITHELIUM
• Avascular tissue composed of cells,
1. Covers the exterior of body surfaces
2. Lines internal body cavities & body tubes
3. Forms parenchyma of glands their ducts
4. Specialized epi cells fxn as receptors for the
special senses.
•
•
Nourished by connective tissue
Regenerate & repair quickly

12. FUNCTIONS
1.
2.
3.
4.
5.
6.
Protection
Absorption
Secretion
lubrication
Transportation
Receptor fxn ( sensory)

13. Characteristics
1. Cell junctions:- specific cell-to-cell adhesion
molecules.
2. Exhibit functional & morphological polarity
a) Apical domain
b) lateral domain
c) basal domain
3. Rest on basement membrane
- anchors epithelial cells to underlying connective tissue

14. CLASSIFICATION
• Based on 2 factors:1. Simple / Unilaminar
2. Compound / Stratified /
Multilaminar

15. Based on the shape of surface cells:-
W>H
W=H
H>W

16. EPITHELIUM
UNILAMINAR/ SIMPLE
MULTILAMINAR/ SRTATIFIED
SQUAMOUS
STRATIFIED SQUAMOUS
CUBOIDAL
COLUMNAR
KERATINIZED
WITHOUT SPECIALIZATION
NON-KERATINIZED
WITH SPECIALIZATIONS
STRATIFIED CUBOIDAL
MICROVILLI
STRATIFIED COLUMNAR
PSEUDOSTRATIFIED
NONCILIATED
SENSORY CELLS
GLANDULAR CELLS
CILIATED
MYOEPITHELIAL CILIA
CILIA
TRANSITIONAL
STEREOCILIA

17. Classification of Epithelial Tissue

18. Simple Squamous Epithelium
• Structure
– Single Layer of flattened cells
• Function
– Diffusion and filtration
– Not effective protection – single
layer of cells.
• Location
– Endothelium
– Mesothelium
– Lung alveolus

19. Simple Cuboidal Epithelium
• Structure
– Single layer of cube shaped
cells
• Function
– Secretion and
transportation in glands,
filtration in kidneys
• Location
– Glands and ducts (pancreas
& salivary), kidney tubules,
germinal layer ofovaries

20. Simple Columnar Epithelium
• Structure
– Elongated layer of
cells with nuclei at
same level
• Function
-- Absorption, Protection
& Secretion
• Location
-- GIT

21. Simple Columnar Epithelium with
specializations
1. Ciliated columnar epithelium:-cell surface bears cilia.
-lines the resp tract, uterus, uterine
tubes.
2. Simple columnar epithelium with
microvilli:-visible only under EM.
-striated border:- small intestine
- brush border:- GB
- increase surface area & absorption
rate

22. Simple Columnar Epithelium with
specializations
3. With secretory
function: Goblet cells
- scattered in the
mucosa of stomach &
small intestines
- single cell glands,
produce protective
mucus.

23. Stratified Squamous Epithelium
• Structure
Many layers (usually Cuboidal/columnar at base & squamous
at surface)
 Found in those surfaces subject to friction.
• Function
– Protection
– Keratin (protein) accumulates in older cells near the
surface
• waterproofs and toughens skin
• Keratinized/ Non-keratinized

24. Stratified squamous
keratinized
• Loc:- skin
• Superficial cell die &
lose their nuclei
• Keratin (+)

25. Stratified squamous non-keratinised
• Loc:Mouth, tongue,
pharynx, esophagus,
vagina & cornea.

26. Stratified squamous epithelium
• Eg..
vagina

27. Stratified Cuboidal epithelium
• Loc:-large ducts of
sweat glands, salivary
glands, pancreas.

28. Stratified columnar epithelium
• Loc:- palpebral
conjunctiva

29. Special classification of epithelium
1. PSEUDOSTRATIFIED
EPITHELIUM
• Structure
– Irregularly shaped cells with nuclei at
different levels – appear stratified, but
aren’t.
– All cells reach basement membrane
• Function
– Absorption and Secretion
– Goblet cells produce mucus
– Cilia (larger than microvilli) sweep mucus
• Location
– Respiratory Linings & Reproductive tract

30. 2. TRANSITIONAL
EPITHELIUM
• Structure
– Many layers / Stratified epithelium
– Very specialized
• cells at base are cuboidal or
columnar, at surface will vary.
– Change between stratified & simple
as tissue is stretched out.
• Function
– Allows stretching (change size)
– Impermeable to salts
• Location
– Urinary bladder, ureters & urethra

31. URINARY
BLADDER

32. Apical domain and its
modifications
-exhibits special structural surface
modifications to carry out specific
fxns.

33. 1.
Microvilli
- fingerlike cytoplasmic projections
- increase surface area for absorption
- length= 5 µm
- vary
a) short, irregular, bleb-like (transepithelial transport is less).
b) tall, closely-packed, uniform ( transport fluid & absorb metabolites).

34. 2. STEREOCILIA
• Extremely long,
immotile microvilli.
• length= 5-10 µm
Limited to:• Epididymis
• Proximal part of
ductus deferens
• Sensory cells of the
inner ear
In EM:- hairs of a paint
brush

35. 3. Cilia
- hair like extensions of apical plasma membrane containing anoxeme.
- motile extensions
 Moves mucus, etc. over epithelial surface
 5-10 µm : length
 0.2 µm : diameter

36. 3 Types of cilia
1. Motile:- large no. (+)nt on the apical domain of many epithelial
cells.
2. Primary / Monocilia:- solitary projections, Immotile
- single cilium per cell (+)nt
fxn:- Chemosensors mediate light sensation
Osmosensors Odorant
Mechanosensors sound perception in
multiple organs in the body
3. Nodal cilia:-Found in the embryo on the bilaminar germ disc
-Concentrated in the area that surrounds the primitive node.

38. Lateral domain & its
specializations
• Characterized by the presence of  CAMs

39. Classification of cell contacts
• Unspecialized contacts
-Cell adhesion molecule
- Each CAM is in contact with
intermediate protein.
-Force is transmitted from
cytoskeleton of one cell to
another.
-TEM:- bead-like

40. Specialized junctional structures
• Forms the barrier & attachment device junctional
complex responsible for joining cell together.
• Three types:1. Anchoring jxns
2. Occluding jxns/ tight
cell to cell contact:
jxns / Zonula occludens
(a). Macula adherens
(Desmosomes)
(b). Zonula adherens
3. communicating jxns/ Gap
(Adhesive belts)
jxns
Cell to extracellular matrix :
(a) Focal adhesions / Adhesive strips
(b) Hemidesmosomes / Focal spots

41. Desmosomes

43. Zonula adherens

44. ANCHORING
JUNCTIONS
DESMOSOME
ZONULA ADHERENS

45. Fascia adherens

46. Hemidesmosomes

48. Occluding junctions

49. Gap junctions

51. TYPES OF CELL JUNCTIONS

52. TYPES OF CELL JUNCTIONS

53. Basal domain
BASEMENT MEMBRANE
• Amorphous, dense layer of
variable thickness at the
basal surfaces of epithelia.
• Consists of:
1. Basal lamina
a). Lamina densa
b). Lamina Lucida
2. Reticular lamina
• Visible under LM

54. BASEMENT MEMBRANE
• Functions:
1. Adhesion
2. Act as barriers
3. Cell organization
4. Regeneration of
peripheral nerves
after injury

55. GLANDS
EXOCRINE GLANDS
ENDOCRINE GLANDS
-Consists of duct
- Lacks duct system
-Secretes their product into the
- Secrete their product into the CT
surface directly / thru the duct
 enter bloodstream  reach
target cells
-Secretion: Unaltered, concentrated -product called as HORMONES
- Sweat, Oil glands, Salivary glands,
- Thyroid, adrenal and pituitary
Mammary glands.
glands

56. Classification of Exocrine glands
1. Unicellular
- simplest, single cell
- Unbranched duct
2. Multicellular / compound
- > one cell
- Branched duct

57. 1. Tubular:- tube like
2. Alveolar/ Acinar:- flask shaped
3. Tubuloalveolar:- tube ends in sac like dilation
** Tubular secretory portions:- straight,
branched, coiled
** Alveolar portions:- single / branched

59. Modes of Secretion
1. Merocrine Glands:•
secretory products del
in membrane bounded
vesicles apical surface of
cells extrude by exocytosis
•
Eg.. Pancreatic acinar cells,
sweat gland, salivary glands

60. Modes of Secretion
2. Apocrine Glands:• Secretory product
released in apical
portion of cell
surrounded by a thin
layer of cytoplasm
within an envelope of
plasma membrane.
•
Eg.. Mammary gland,
ceruminous gland of
ext auditory meatus

61. Modes of Secretion
3. Holocrine Glands:• Secretory product
accumulates within the
cell programmed cell
death
• Sec products & cell
debris discharged into
lumen
• Eg.. Sebaceous gland of
skin, meibomian glands

62. PARACRINE GLANDS
• Secretory material reaches
the target cells by diffusion
through the extracellular
space / subjacent CT.
ENDOCRINE GLANDS
• Eg… Pituitary gland, ovaries,
testes, pancreas
Thyroid gland, Adrenal
gland

63. DISCUSSION