Exocrine glands are glands of the exocrine system that secrete their essential product by way of a duct to some environment external to itself, either inside the body or on a surface of the body. Exocrine glands are one of two types of glands in the human body, the other being endocrine glands, which secrete their products directly into the bloodstream. Examples of exocrine glands include the sweat glands, salivary glands, mammary glands, and liver.
Serous cells excrete proteins, often enzymes. Examples include chief cells and Paneth cells
Mucous cells excrete mucus. Examples include Brunner's glands, esophageal glands, and pyloric glands
Mixed glands excrete both protein and mucus. Examples include the salivary glands, although the parotid gland is predominantly serous, the sublingual gland is predominantly mucous, and the submandibular gland is both serous and mucous.