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