The body glands are classified into two main groups:
(i) Exocrine glands: The secretions of these glands are carried by ducts to a particular organ for some metabolic activity. e.g., salivary glands, liver etc.
(ii) Endocrine glands: These glands have no ducts and their secretions get absorbed into the immediate surrounding blood circulation to reach specific organs to initiate a particular metabolic change. e.g. pituitary, thyroid.