2. Professors of Hisology and Cell Biology
The epithelium By
Dr. Ibtehag El Ghazzawy
&
Dr. Nahed Zohdy
Professors of Hisology and Cell Biology

3. 4 Basic Types of Tissues Connective tissue Muscular tissue
Epithelial tissue
Nervous tissue

4. Epithelial Tissue
(The epithelium)

5. General features of epithelium
Closely aggregated cells
Very little intercellular substances
Regular shaped cells bind together by junctional complexes
Basal lamina (basement membrane)
Avascular
Rich in nerve supply
High renewal rate

6. Classification of epithelium
-Covering and lining epithelium
-Glandular (secretory) epithelium

7. Classification of covering &lining epithelium
Number of layers
Shape of cells
Squamous
Cuboidal
Columnar
Simple
Stratified

8. 1- Simple Squamous Epithelium
LM:
Surface view

9. Simple Squamous Epithelium (Bowman’s capsule- kidney)
LM:
Side view
Function: Filtration of blood

10. Simple Squamous Epithelium (Lung alveoli)
Function: gas exchange

11. 2- Simple cuboidal Epithelium Site:Thyroid gland- kidney tubules
(ion exchange)

12. 3- Simple Columnar Epithelium
Types:
a. Non ciliated
b. Ciliated

13. a. Simple columnar epithelium (non ciliated)LM
Sites: ducts of glands- digestive tract
(secretion or absorption)

14. b. Simple columnar epithelium ciliated
Sites: uterus, oviduct & bronchiole of the lung
(movement of luminal contents)

15. 4- Pseudostratified columnar epithelium
False

16. a- Pseudostratified columnar epithelium non ciliated
Sites: Male genital tract – large ducts of glands: (secretion)

17. b. Pseudostratified columnar epithelium ciliated
Sites: Nose- Trachea (protection)

18. 2- Stratified Epithelium
What cell is on the top layer?
Stratified sqamous epithelium
Stratified cuboidal epithelium
Stratified columnar epithelium
Transitional epithelium

19. Stratified Squamous Epithelium

20. Non Keratinized Keratinized
Stratified squamous epithelium
Non Keratinized Keratinized
Oesophagus- vagina skin
(Physical protection)

21. Stratified cuboidal Epithelium (Rare)

22. Stratified Cuboidal Epithelium (Ducts of sweat glands: secretion)

23. Stratified Columnar Epithelium (Rare)
- ciliated: penile urethra
- Non ciliated: conjunctiva
(protection)

24. Transitional epithelium
(urinary bladder - empty)

25. Transitional Epithelium Empty urinary bladder

26. Transitional Epithelium Full urinary bladder

27. Transitional epithelium

28. Transitional epithelium
Adaptation of Transitional epithelium to its function:
Thin corrugated basement membrane
Abundant mucoid intercellular substance to allow gliding of cells on each other.
Cuticular border at the free surface.

29. Glandular Epithelium
Origin
differentiation

30. Types of glandular epithelium
It is classified according to:
1- Number of cells
2- Presence or absence of a duct system
3- Mode of secretion (mechanism)
4- Nature of secretion
5- Shape of the secretory portion

31. Unicellular(goblet cell)
1-Number of cells
Unicellular(goblet cell)
Multicellular
(Salivary glands) 31

32. Goblet cells EM

33. 2-Mechanism (Mode) of Glandular secretions
a. Merocrine glands
The secretions are released through exocytosis
Pancreas

34. b. Apocrine glands
The secretion involves the loss of both product and apical cytoplasm
Mammary glands

35. c. Holocrine gland
The secretion destroys the cell
Sebaceous glands

36. 3- Presence or absence of a duct system Exocrine Endocrine mixed36

37. Mode of secretion
(apocrine)

38. 4- Nature of Glandular secretions sebaceous gland (oily secretion)
Serous glands: parotid gland
Mucous glands: sublingual gland
Mixed glands: submandibular gland
Glands with special secretion:
sebaceous gland (oily secretion)

39. 5- The shape of secretory portion

40. Classification of Tubular Glands simple: unbranched duct
Intestinal glands Sweat glands Fundic glands

41. Classification of Alveolar Glands
Sebaceous glands Tarsal glands

42. Classification of Compound Glands
Compound: branched duct
branched secretory portion
Liver mammary glands salivary glands

43. Special types of epithelium (Taste buds: dorsal surface of the tongue)
1-Neuroepithelium
(Taste buds: dorsal surface of the tongue)

44. 2. Germinal epithelium
Testis: sperm
Ovary: ovum

45. Functions of epithelium
Protection
Secretory
Absorption
Filtration and gas diffusion
Sensation (neuroepithelium)
Reproduction (germinal epithelium)