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.

Structural classification of exocrine glands:

Multicellular exocrine glands are classified by structure ,using the shape of their ducts and the complexity(branching) of their ducts system as distinguishing characteristics. Shape include tubular and aveolar(Sac like).Simple exocrine glands e.g.,intestinal gland, mammalian sweat glands,cutaneous glands of frog etc.have only one duct leading to surface .Compound exocrine glands have two or more ducts e.g.,liver,salivary glands etc.

Type Example
Simple tubular Intestinal glands,crypts of Lieberkuhn in ileum.
Simple coiled tubular Sweat glands in man.
Simple branched tubular. Gastric (stomach) gland,and Uterine gland.
Simple alveolar Mucous gland in skin of frog,Poison gland of toad and seminal vesicle.
Compound tubular Brunner's gland ,bulbourethral gland and liver.
Compound alveolar. Sublingual and submandibular salivary gland.
Compound tubulo alveolar. Parotid salivary glands,Mammary gland and Pancreas.

Classification of glands on the basis of their mode of secretion

Classification of glands on the basis of their mode of secretion

(i)Apocrine gland:

Apocrine glands collect their secretory products near the apex or tip,of the cell
and then release it into a duct by pinching off the distended end.

Apocrine glands collect their secretory products near the apex or tip,of the cell and then release it into a duct by pinching off the distended end.This process results in some loss of cytoplasm and damage to the cell.e.g.,Mammary glands.(Modified sweat gland)

(ii)Holocrine gland:

Holocrine glands collect their secretory products inside the cell and then rupture
completely to release it.

Holocrine glands collect their secretory products inside the cell and then rupture completely to release it.These cells self destruct to complete their functions.e.g., Sebaceous gland.In case of rabbit sebaceous glands are found in dermis of skin.Pineal body and thymus can also be considered as holocrine gland.

(iii)Merocrine gland:

Merocrine glands(Eccrine or Epicrine gland) discharge their secretory product
directly through the cell or plasma membrane

Merocrine glands(Eccrine or Epicrine gland) discharge their secretory product directly through the cell or plasma membrane,without injury to the cell wall and without loss of cytoplasm.e.g.,Sweat glands,exocrine region of vertebrate pancreas,salivary glands and intestinal glands etc.


Classification of glands on the basis of nature of product

Mucous gland:

Secret slimy mucous e.g.,goblet cells,palatine gland,gland of uterus,some gastric gland
and gland of colon.

Secret slimy mucous e.g.,goblet cells,palatine gland,gland of uterus,some gastric gland and gland of colon.

(ii)Serous gland:

Produce watery secretion.e.g., pancreas,parotid,salivary gland,sweat gland and intestinal gland.

(iii)Seromucous gland:

Secrete mixed liquid.e.g.,Most gastric gland,sublingual, submaxillary salivary gland, pancreas.

(iv)Cytogenic gland:

They produce cells e.g., Testes and ovary.

Connective tissue

It connects and support all the other tissues,the intercellular element predominating.
 The cellular element is usually scanty.