exocrinos

Exocrinos, also known as exocrine glands, are glands that produce secretions released onto an epithelial surface or into a body cavity via ducts. They contrast with endocrine glands, which secrete hormones into the bloodstream. Exocrine secretions include enzymes, mucus, bile, sweat, tears, and digestive juices.

Structure and classification: Exocrine glands consist of secretory units and a duct system. They can be unicellular, such as goblet cells, or multicellular. Multicellular glands are further classified by duct pattern as simple (unbranched) or compound (branched) and by the shape of the secretory unit as tubular, acinar, or tubuloacinar. Secretions are released by different modes of secretion, including merocrine (exocytosis), apocrine (partial loss of cytoplasm), and holocrine (cell disintegration).

Common examples and function: The major exocrine glands include salivary glands (parotid, submandibular, sublingual) that produce saliva; the pancreas (exocrine portion) that delivers digestive enzymes and bicarbonate into the small intestine; and sweat glands that secrete sweat onto the skin. Goblet cells are unicellular exocrine glands that secrete mucus within the respiratory and intestinal tracts. The liver and biliary system contribute bile through ducts, representing exocrine-like secretion from an organ system rather than classic glands.

Clinical relevance: Exocrine function can be impaired by genetic, inflammatory, or obstructive diseases. Cystic fibrosis, for example, affects pancreatic and respiratory exocrine secretions, leading to digestive and lung problems. Sjögren's syndrome involves reduced exocrine secretion from salivary and lacrimal glands, causing dryness. Obstruction or inflammation of ducts can also disrupt exocrine output and organ function.