exocrín

Exocrín is a term used in biology to describe glands that secrete substances through ducts onto an epithelial surface. These secretions can be released either onto the surface of the body, such as sweat or oil glands, or into the lumen of organs like the digestive tract. The term "exocrine" comes from the Greek words "exo" meaning outside and "krinein" meaning to secrete. This is in contrast to endocrine glands, which secrete hormones directly into the bloodstream without the use of ducts.

Exocrine glands are diverse and perform a wide range of functions. For example, salivary glands secrete saliva into the mouth to aid in digestion and lubrication. The pancreas has both exocrine and endocrine functions; its exocrine portion produces digestive enzymes that are released into the small intestine. Sebaceous glands in the skin produce sebum, an oily substance that lubricates and waterproofs the skin and hair. Sweat glands produce sweat to help regulate body temperature.

The secretions of exocrine glands can be categorized into three types based on their mode of release. Merocrine secretion involves the release of substances contained within vesicles that fuse with the cell membrane, emptying their contents without damaging the cell. Apocrine secretion involves the shedding of a portion of the apical cytoplasm, which contains the secretory product. Holocrine secretion involves the entire cell rupturing and releasing its contents, with the cell being replaced by a new one. Understanding the mechanisms of exocrine secretion is crucial for comprehending various physiological processes and pathological conditions.