A power point presentation made with hard work, collecting material from various authentic and reliable sources. Best ppt for under grad as well as for post grad students.

1. Normal epithelium
By: Dr. Ahmad Abubakr
PGT Histopathology

2. Definition:
An epithelium is a type of animal tissue made up
of densely packed cells (called epithelial cells) that rest
on a basement membrane.
Epithelium forms continuous sheets of cells that
line internal surfaces of hollow organs and cover the
external surface of the body.
It is a selective barrier that protects tissues and is
often involved in absorption or secretion.
A basement membrane separates an epithelium
from the underlying connective tissue.

3. Classification of Epithelium
• Can be classified as:
1. Number of cell layers
• Simple (single layer of cells)
• Stratified (more than one layer of cells)
• Pseudostratified
2. Cell shape
• Squamous
• Cuboidal
• Columnar
• Transitional

4. 3. Specialisations:
• Microvilli
• Cilia
• Keratin
• Goblet cells
4. Types:
• Covering epithelium
• Glandular epithelium

5. Simple squamous epithelium:
• Single layer of cells
• cells are flat, width is much greater than height.
• Commonly found in alveoli of lungs, blood
vessels
• Plays role in diffusion

6. Simple cuboidal epithelium:
• Single layer of cells
• cells appear approximately square
• Commonly found in PCT and DCT of
kidneys, thyroid follicles
• Plays role in absorption and secretion

7. Simple columnar epithelium:
• single layer of cells with nuclei at same level
• height is greater than width
• Can be ciliated and non ciliated
• Commonly found in trachea, bronchi, alimentary
canal and uterine tubes
• Plays role in absorption and movement of
mucus

8. Pseudostratified epithelium:
• Single layer of cells but nuclei are at different
levels so apparently looks more than one layer
• All cells rest on basement membrane, but all
cells don't reach the surface
• Located in upper respiratory tract
• Secretes and moves mucus

9. Transitional epithelium:
• A special form of epithelium, in which the cells can
alter their shape.
• When the epithelium is relaxed they appear
cuboidal but when stretched they appear
squamous.
• Found in urinary tract

10. Stratified squamous epithelium:
• Two or more layers of cells
• Located in skin, mouth, esophagus
and vagina
• Protects against abrasions

11. Stratified cuboidal epithelium:
• Two or more layers of cells
• Found in sweat glands and salivary glands

12. Stratified columnar epithelium:
• Two or more layers of cells
• Located in urethra and some glands

13. Microvilli:
• Fine, finger-like projections
which contain a central core of
microfilaments
• Increase the apical surface area
in cells.
• They help absorption (e.g.
intestinal cells).

14. Cilia:
• Long, motile projections of the apical
surface.
• These are longer than microvilli.
• Contain a core of microtubules and
beat synchronously.
• Found on cells lining the upper
respiratory tract
• Their rhythmic beating moves mucus
upwards in the respiratory tract.

15. Keratin:
• It is a filamentous protein
secreted by the epithelial
cells.
• Found in areas susceptible
to abrasion and water loss
(e.g skin)

16. Goblet cells:
• Type of glandular epithelium
• Epithelial cells are specialised
for secretions
• They secrete mucus onto the
apical surface
• Located in GI tract