Welcome to Zoology World

balindrakumar033@gmail.com   25/11/2017,Saturday

WELCOME TO ZOOLOGY WORLD

The science or study of animal life. Together with botany, the study of plant life, it forms the science of biology. Zoology is such a vast subject that most zoologists specialize or focus on the study of particular organisms or taxonomic groups. tion of animals.

What is compound Epithelium:

It is complex in structure and basically formed by  two or more than  two layers of cells.

It is complex in structure and basically formed by two or more than two layers of cells.


(i) Stratified squamous keratinized epithelium:

It has multicellular layer of cells

Stratified squamous epithelium is characterized by multiple layers of cells with typical flattened squamous cells at the free or outer surface of the sheet.The presence of keratin in these cells contributes to the protective qualities of skin covering the body surface.Keratin is dead and waterproof so it protects the underlying tissues from abrasion and infection e.g.,epidermis of the skin of land vertebrates.


(ii)Stratified squamous non keratinised epithelium:

Its free surface is moist ,and the outer epithelial cells,unlike those found in the skin, do not contain keratin.This type of epithelium serves a protective function.It is found lining the oral cavity(buccal cavity), pharynx,oesophagous,anal canal,lowerpart of urethra, vocal cords,vagina ,cervix(lower part of uterus) and cornea of eyes.


(iii)Stratified cuboidal epithelium:

It consists of two or more rows of low cuboidal
-shaped cells

It consists of two or more rows of low cuboidal-shaped cells which are arranged randomly over a basement membrane.It is found in the sweat gland ducts,large salivary and pancreatic ducts.


(iv) Stratified columnar epithelium:

It is protective  epithelium having multiple layers of  columnar cells

It is protective epithelium having multiple layers of columnar cells,only the most superficial cells are truly columnar in appearance.Epithelium of this type is rare.It is found in male urethra and in the mucous layer near the anus.It also lines mammary gland ducts and epiglottis.


(v) Stratified columnar ciliated epithelium:

It lines the larynx and upper part of the soft palate.


(3) Specialized epithelium:

This type of epithelium are specialized to perform specific activity hence,specialized in structure also.They are as follows:-


(i)Transitional epithelium (Urothelium):

It  is often ten or more layers thick.It lacks germinative layer

It is often ten or more layers thick.It lacks germinative layer,basement membrane. Stratified transitional epithelium is typically found in the body areas such as the wall of urinary bladder ,ureter and renal pelvis.It is located in all the hollow viscera subjected to stress and protects organ wall from tearing.


(ii) Neurosensory epithelium:

Olfactory mucos,called Schneiderian membrane,lining of internal nares,retina of eyes