Stratified Epithelial Tissue | Biology for Grade 11 PDF Download

Stratified Epithelial Tissue

Stratified epithelium possess many layer of epithelial cells, the deepest layers is made up of cuboidal/columnar cells.

On the basis of shape of the cells of outermost layer it is of four types:

(1)  Stratified Squamous Epithelium 

(2)  Stratified Cubical Epithelium 

(3)  Stratified Columnar Epithelium  

(4) Stratified Ciliated Columnar Epithelium

(1) Stratified Squamous Epithelium

• Innermost layer of cells are of cuboidal or columnar shaped.  
• These cells have high Mitotic index.
• They divide to form layer of Stratified epithelium so this layer is called as Germinativum layer. 
• Middle layers are made up of polygonal cells.
• These cells are interconnected with Desmosomes which provide rigidity or mechanical support.
• Cells of outermost layer are scale like flat cells.

On the basis of presence or absence of Keratin protein in the outer most cells this epithelium is of two types:

A. Keratinized Stratified Squamous Epithelium

Hard water proof keratin protein is present in scaly cells and cells become non nucleated dead cells.

eg., Epidermis of skin, Scale, Horn, Nails, Feathers

B. Non Keratinized Stratified Squamous Epithelium  

(2) Stratified Cubical Epithelium

• Outermost layer of cells are cube like & cells are nucleated & living. 
• Middle layer – polygonal shaped cells.
• E.g. Secretory duct of sweat glands, mammary glands and sebaceous gland.

(3) Stratified Columnar Epithelium

• It consists of columnar cells in both superficial as well as in basal layers. 
• Cells are nucleated. 
• Cilia absent on free end.
• E.g., Distal part of male urethra, Epiglottis

(4) Stratified Ciliated Columnar Epithelium 

eg., Larynx, upper part of soft palate, uterus, buccal cavity of frog.

Functional Classification of Epithelial Tissue

Functionally epithelial tissues can be classified as follows :

(a)  Germinal Epithelium : It is present in testis and ovaries. Its cells produce Sperms and Ova.

(b)  Pigmented Epithelium : It is present in retina of eye. It possess pigment which give colour to the retina.

(c)  Sensory Epithelium : It is found in retina of eye, internal ear, nasal chamber and tongue. It perceives stimuli and conducts impulses.

(d)  Glandular Epithelium : It is present in glands and secrete fluid (Secretion)

(e)  Absorptive Epithelium : It is found in nephron of kidneys, stomach, intestine, It helps in absorption of food in stomach and intestine and liquid materials in nephron.