Classification according nature of secretion

Secretory units may be mucous, serous or mixed.

Mucous glands secrete mucinogens, large proteins. Examples of mucous glands include goblet cells and the minor salivary glands of the tongue and palate.

Serous glands such as pancreas secrete an enzyme-rich watery fluid.

Mixed glands contain acini that produce mucous secretions as well as acini that produce serous secretions.

According to the mode of secretion:

In other words, according to how the secretory cells release their secretion.

A) Merocrine glands;

In this type, the membranes of the secretory vesicles fuse with the cell
membrane releasing their contents of secretion by exocytosis, without
loss of any of the glandular cytoplasm. Nearly, all exocrine glands are
of this type.

B) Holocrine glands;

In this type, the whole of the cell, together with its accumulated
secretion, is shed and liberated out of the secretory unit. A good example
of this type is the sebaceous gland of the skin.

C) Apocrine glands:

The secretory granules are liberated with some of the cytoplasm of the apical part of the secretor cell. Examples of these glands are the mammary glands and the special types of sweat glands.

Blood

Blood is a fluid connective tissue that circulates through the cardiovascular system.

Blood consists of formed elements, cells and their derivatives and a protein-rich matrix called plasma.

Дата добавления: 2015-07-25