The characters of glands based on the type of release of secretion
Glands may also be classified into three categories based on the mode of releasing the secretion. These are exocrine, endocrine, and heterocrine. The exocrine glands send their secretions through the ducts to the sites of action. These include salivary glands, gastric glands, intestinal glands, tear glands, mammary glands etc.,
The endocrine glands are often called ductless glands because they discharge their secretions directly into the blood stream and they are carried to the sight of action along with the blood. The secretions of endocrine glands are usually called hormones. Examples of endocrine glands are thyroid glands, parathyroid, adrenals, pituitary, thymus etc. The heterocrine glands have the combined characteristics of both endocrine and exocrine in that the secretion is first re
leased by way of duct and the product then is directly carried into the blood. Pancreas may be said to be a heterocrine gland.