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.

Gland

A cell,tissue or organ which
secretes a useful chemical material is known as gland

Glandular epithelium are specialized for secretory activity.A cell,tissue or organ which secretes a useful chemical material is known as gland.Glands are made up of cuboidal epithelial cells which are more secretory.All glands arise as folding of epithelia. The golgi body in gland cells are larger and more secretory.Most of the glands of body are merocrine types.It originate from all three germinal layers.(ecto,meso and endoderm). Liver is the largest gland of the body and lined by glandular epithelium.

Types of glands:

(A) On the basis of number of cells

(i) Unicellular gland:

It consists of unicellular gland cells which are called as goblet cells

It consist of unicellular gland cells which are called as goblet cells or chalice cells. They secrete mucous and found in mucosa of intestine and stomach.Mucous lubricates the food for easy peristalsis. Their life span is about 2-3 days.

(ii)Multicellular gland:

It consist of many cells and are generally located  in unerlying  connective tissue

It consist of many cells and are generally located in unerlying connective tissue. e.g.,gastric and intestinal glands.


(B) On the basis of presence or absence of ducts:

(i) Exocrine gland:

(ii)Multicellular gland:

These are those glands which discharge their secretory  products into  ducts.

These are those glands which discharge their secretory products into ducts.It is also called ducted glands or glands of external secretion. e.g.,Salivary glands,Mammary glands and Tear glands.

(ii)Endocrine gland:

They are often called ductless gland,because they discharge their secretory products(Hormone)
directly into the blood

They are often called ductless gland,because they discharge their secretory products(Hormone) directly into the blood.e.g.,Pituitary gland,thyroid ,parathyroid and adrenal glands.

(iii)Heterocrine gland:

These are those glands which are partly endocrine and partly exocrine in function

These are those glands which are partly endocrine and partly exocrine in function. e.g.,Pancreas.


Structural classification of exocrine glands: