Exocrine glands produce and release a variety of glandular products. Exocrine glands can be classified into serous, mucous, or mixed types based on their secretory products.
Serous glands produce watery secretions rich in digestive enzymes and proteins. The constituent cells of the serous gland have centrally located nuclei and eosinophilic secretory granules in the cytoplasm. The parotid gland is an example of a serous gland. It secretes saliva, which contains enzymes, such as lipases and amylases that help digest the food.
Mucous glands release viscous products rich in the glycoprotein mucin. The constituent cells of mucous glands are characterized by flattened nuclei located at the basal surface of the cells and cytoplasm filled with secretory granules. Examples of mucous glands include sublingual salivary glands and the submucosal glands of the small intestine.
Mixed exocrine glands contain both serous and mucous glands and release both types of secretions. Submandibular salivary glands are examples of mixed glands.
This text is partially adapted from Openstax, Anatomy and Physiology 2e, Section 4.2: Epithelial Tissues
