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Note on Epithelial Tissue -1

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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.

  1. epithelium described by Ruysh andectodermal , mesodermal , endodermal in origin 
  2. the cells have height or thinckness more than length or breadth 
  3. epithelium is single cell thick but appears to doublar layers due to presence of different level of height of celss and postion of nuclei
  4. Cells coitntaing microvilli which increase the surface area for proper absorption 
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