Epithelial Tissue -1

Epithelium tissue
# epithelium described by Ruysh.
# ectodermal , mesodermal , endodermal in origin.
# covers the body surface.
# Cilia ,flagella, and demososomes are usually associated with such tissue.

Simple epithelium tissues
Epithelium is one-celled thick they are of four types
1 squamous epithelium 3 Columnar epithelium
2 cuboidal epithelium 4 specialized epithelium

1 squamous epithelium -
* also called as pavement epithelium.
* the cell resembles floor tiles.
* the length and breath of the cells are more than the thickness of the cell.
* Examples are alveolar epithelium , the inner lining of bowman’s capsule , capillary epithelium , eye – lense epithelium.

2 columnar epithelium
* the cells have height or thickness more than length or breadth.
* such epithelium lining have or are grandullar or secretory .
*examples are – lining of Acini of pancreas , lining of all bladder ,stratum germinativum of skin and lining of stomach.

3 cuboidal epithelium
* the cells are cubidal having similar length height and breadth .
* examples are germinal epithelium , follicular ,linin of DCT,ascending limb of Henley.

4 Specialized epitheium
are divided into 4 types
a Pseudostratified epithelium
* epithelium is single cell thick but appears to double layers due to the presence of a different level of height of cells and position of nuclei.
* the tall cells are ciliated where as shorter cells are nonciliated.
* Examples are epithelium of trachea and bronchi
b sensory epithelium
* these are innervated and receive various types of stimuli .
* Examples are retina, schenedarian membreans and labyrinth.
c Brush bordered
* Cells coitntaing microvilli which increase the surface area for proper absorption .
* these microvilli may be small or regular.
* Examples is epididymis
d Ciliated epithelium
* over all surface cells are ciliated.
* these cells help in movement of sperm in vas deferens ,oviduct or movement of muscus from trachea into pharynx.

Transitional epithelium
*it is 2-6 cell thick.basement membrane absent.
*it occers in the area where stretchings is reqired or flexn and extension.
* example are in urinary bladder,ureter and pelvis.

Stratifed epithelium
* the epithelial layer is more than 6 cells thick epithelium.
* basement membrane is present but are single.
* Examples are buccal cavity ,skin,pharynx,oesophagus,vaginal epitheilium .
1 Stratified Squamous epithelium – common stratified ,are squamous ,Examples are buccal cavity
2 Stratified Cuboidal epithelium – present at mammary gland and sweat glands
3 Stratified Colunar epithelium – mainly presnt at embryonic tissue and poorly in developing adults

Reference:

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.