In how many groups are body glands classified?

The body glands are classified into two main groups:
(a) 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.
(b) 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.