The Basis Of Classification Of Gland By Nandeshori Devi Konthoujam At Isnare.com Ezine Articles

Gland is the biological term used that signifies one or many associated cells that secrete or excrete one or more specialized substances. The glands are several types in the animal body on different basis for classification. According to the number of cells glands are classified as unicellular, multicellular glands. The multicellular glands are simple, unbranched, and tubular as sweat glands; compound branched tubular as mammary glands of prototherians; simple but branched flasked shaped glands as present along the margins of eyelids; simple flask shaped alveolar as the mucous glands of frog’s skin, alveolar gland or compound succular gland as mammary glands of other mammals.

According to the mode of secretion the glands may be divided as merocrine, holocrine, apocrine and eccrine. In merocrine the cells discharges their secretions causing much damages to the cells and the cells have to undergo a period of rest like the mucous gland of amphibian skin, whereas in holocrine glands the cells when full with capacity die and products are discharged from the epithelial walls like sebaceous glands. In case of the apocrine glands the products are collected at the outer part of the cells like mammalian sweat glands and the eccrine glands are similar to the apocrine glands but the cytoplasm is broken down before the products are discharged like sweat glands.

With respect to the place of discharging their products the glands are divided into exocrine and endocrine glands. The exocrine glands are those which remain connected to the surface of the epithelium by the ducts through which they discharge their secretions onto the epithelial surface. The secretion of the exocrine glands reaches the outside of the body directly or indirectly whereas those of endocrine glands secretes into the blood or lymph vessels. The exocrine glands (duct ness) are further divided into the following groups 0n the basis of the shape of the secretary parts of the glands as:

1. Simple tubular: intestinal crypts of leiberkuhn.

2. Simple coiled tubular: ordinary sweat glands.

3. Simple branched tubular: fundic glands of stomach, deep glands of the duodenum.

4. Simple alveolar: mucous and poison glands of amphibian skin.

5. Simple branched alveolar: meibomian and sebaceous glands.

6. Compound tubular: Brunner’s gland in duodenum.

7. Compound alveolar: lactating mammary gland.

8. Compound tubulo alveolar: sub maxillary gland, pancreas, large glands of the esophagus and respiratory tract.

Endocrine glands are the ductless glands are the organs whose function in the body is to secrete hormones. Common examples of endocrine glands are the pituitary (anterior and posterior pituitary,), the thyroid, the parathyroid, pancreas, pineal, gonads and the adrenals. The endocrine glands secrete their secretions that are the hormones into the blood stream. The functioning of the body is controlled by the hormones secreted by the glands at a greater extend. The hormones are released in the blood and are circulated along with it and transported to the target organs. The glands in the animal body are divided into different types on several criterions.

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