Sekretion

Sekretion is the biological process by which cells and tissues produce and release substances for use within an organism or for the exterior environment. It encompasses a wide range of products, including enzymes, hormones, mucus, bile, and milk, and occurs in many animal organs as well as in plants.

Glands and secretory tissues are commonly categorized by destination: exocrine secretion, which releases products through ducts to surfaces or body cavities, and endocrine secretion, which releases hormones directly into the bloodstream. Subtypes of secretion describe how cells discharge their products: merocrine secretion involves vesicles fusing with the cell membrane to release contents by exocytosis; apocrine secretion releases a portion of the cell’s apex along with its contents; holocrine secretion results from the complete destruction of the secretory cell, releasing its accumulated material.

The secretory pathway typically starts with synthesis in the rough endoplasmic reticulum, followed by processing and packaging in the Golgi apparatus, and transport to the cell membrane for release via vesicles. Secretion is often regulated by hormones, neural input, or other signals, allowing rapid or sustained release as needed.

Examples include saliva and digestive enzymes from salivary and pancreatic glands, mucus from goblet cells, insulin from pancreatic beta cells, bile produced by the liver, and milk from mammary glands. In plants, sekretion also occurs in nectar production, resin exudation, and latex release.

Secretion is distinct from excretion; secretion involves producing and releasing functional substances, while excretion refers to the elimination of waste products. The term sekretion is commonly used in German and related languages, with secretion serving as the English equivalent.