exokriner

Exokriner, commonly rendered in English as exocrine, refers to glands, tissues, or secretions that discharge their products through ducts onto an epithelial surface or into a body cavity, rather than releasing them into the bloodstream. The term comes from Greek exo- “outside” and krinein “to secrete.” Exocrine secretions serve local functions, in contrast to endocrine secretions, which act as hormones within the circulatory system.

An exocrine gland consists of secretory units and a duct system. Secretions can include enzymes, mucus, electrolytes, and antimicrobial agents. Common examples are the salivary glands delivering saliva into the mouth, lacrimal glands to the eye, gastric glands to the stomach, sweat glands to the skin, and the exocrine part of the pancreas releasing digestive enzymes into the duodenum.

Glandular secretory mechanisms include merocrine, apocrine, and holocrine modes. In merocrine secretion, secretory products are released by vesicle fusion with the cell membrane. In apocrine secretion, a portion of the cell membrane and cytoplasm is shed with the product. In holocrine secretion, the entire secretory cell disintegrates to release its product. Exocrine glands can be classified by duct structure as simple or compound and by the shape of the secretory units as tubular, acinar, or tubuloacinar. Secretions may be serous, mucous, or mixed.

Clinical relevance includes conditions affecting exocrine function, such as pancreatic exocrine insufficiency seen in cystic fibrosis or chronic pancreatitis, and exocrine-derived tumors like pancreatic ductal adenocarcinoma. Understanding exocrine biology aids in comprehending digestion, lubrication, and local tissue homeostasis.