Sweat gland

It is one of the skin glands in the subcutaneous tissue that secretes sweat. It is an exocrine gland, and its ducts are called sweat ducts. They are long and cylindrical, and ascend in a slight spiral shape through the subcutaneous tissue and dermis, enter the epidermis between the dermal papillae, and finally open at the top of the skin ridge, which is the highest part of the integument surface. The opening is called a sweat pore. Sweat glands are divided into eccrine glands (small sweat glands) and apocrine glands (large sweat glands), which are morphologically and physiologically different. Special types include the eyelash glands near the base of the eyelashes, as well as the perianal glands and ear canal glands (ear wax glands), but all of them belong to the apocrine gland. Eccrine glands are sweat glands that secrete large amounts of moisture and are involved in thermoregulation, and are distributed independently of hair, whereas apocrine glands in humans have degenerated and are localized with hair in the armpits and are not involved in thermoregulation. There is no fundamental difference between the two in terms of anatomy or secretory physiology, and it is recognized that the two are a series of changes that occurred along the evolutionary process from apocrine glands to eccrine glands.

[Kimiko Saito]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

皮下組織内にある皮膚腺の一つで、汗を分泌する。外分泌腺で、その導管は汗管とよばれ、細長い円筒形で、皮下組織と真皮の中を軽く螺旋(らせん)状に曲がりながら上行し、真皮乳頭の間から表皮に入り、最後には外皮表面の最高部である皮膚小稜(しょうりょう)の頂に開口する。その開口部を汗孔（汗口）という。汗腺は形態的、生理的に異なるエクリン腺（小汗腺）とアポクリン腺（大汗腺）に分けられる。特殊型としてまつげの根部近くにある睫毛腺(しょうもうせん)をはじめ、肛門周囲腺(こうもんしゅういせん)（肛囲腺）や耳道腺（耳垢腺(じこうせん)）があるが、いずれもアポクリン腺に属する。エクリン腺は大量の水分を分泌して体温調節に関与する汗腺で、毛とは関係なく分布するが、アポクリン腺はヒトの場合、退化してわきの下などの毛とともに局在し、体温調節には関与しない。両者は解剖学的にも分泌生理学的にも根本的な差はなく、アポクリン腺からエクリン腺への進化過程に沿った一連の変化であることが認められている。

［齋藤公子］

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