villus

/vil"euhs/, n., pl. villi /vil"uy/.
1. Anat., Zool. one of the minute, wormlike processes on certain membranes, esp. on the mucous membrane of the small intestine, where they serve in absorbing nutriment.
2. Bot. one of the long, soft, straight hairs covering the fruit, flowers, and other parts of certain plants.
[1695-1705; < L: shaggy hair, thick nap]

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      in anatomy any of the small, slender, vascular projections that increase the surface area of a membrane. Important villous membranes include the placenta and the mucous-membrane coating of the small intestine. The villi of the small intestine project into the intestinal cavity, greatly increasing the surface area for food absorption and adding digestive secretions. The villi number about 6,000 to 25,000 per square inch (10 to 40 per square millimetre) of tissue. They are most prevalent at the beginning of the small intestine and diminish in number toward the end of the tract.

      The large number of villi give the internal intestinal wall a velvety appearance. Each villus has a central core composed of one artery and one vein, a strand of muscle, a centrally located lymphatic capillary (lacteal), and connective tissue that adds support to the structures. The blood vessels are thought to transport proteins and carbohydrates absorbed by the cells of the villi, while the lymphatic capillary removes droplets of emulsified fat ( chyle). The muscle strand allows the villi to contract and expand; it is believed that these contractions empty the contents of the lacteal into larger lymphatic vessels.

      Covering the core of a villus is the surface mucous-membrane layer. This is mainly composed of two cell types: tall, narrow, columnar cells that absorb the substances passed into the blood and lymphatic vessels; and goblet cells, rounded at the end, that secrete mucus into the intestinal cavity. On the surface of each columnar cell there are about 600 very fine projections called microvilli that further increase the absorptive area of each villus.

      Villi of the intestine move in swaying, contracting motions. These movements are believed to increase the flow of blood and lymph and to enhance absorption. The villi of the small intestine absorb about 2 gallons (7.5 litres) of fluid per day, and absorption seems to be indiscriminate.

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Universalium. 2010.

Look at other dictionaries:

  • Villus — (Latin: shaggy hair [http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0035419.html] Tiscali UK Reference encyclopedia] , plural villi) can refer to: * Intestinal villus. This is the most common meaning when not more precisely… …   Wikipedia

  • villus — 1704, pl. villi, from L. villus “tuft of hair, shaggy hair” (see VELVET (Cf. velvet)) …   Etymology dictionary

  • Villus — Vil lus, n.; pl. {Villi}. [L., shaggy hair, a tuft of hair.] 1. (Anat.) One of the minute papillary processes on certain vascular membranes; a villosity; as, villi cover the lining of the small intestines of many animals and serve to increase the …   The Collaborative International Dictionary of English

  • Villus — (lat.), Zotte; daher Villös, zottig, flockig, faserig, rauh. Villosa tunica intestinorum, innere Haut der Gedärme …   Pierer's Universal-Lexikon

  • villus — ► NOUN (pl. villi) Anatomy ▪ any of numerous minute elongated projections set closely together on a surface, especially in the absorbent lining of the small intestine. DERIVATIVES villous adjective. ORIGIN Latin, shaggy hair …   English terms dictionary

  • villus — [vil′əs] n. pl. villi [vil′ī΄] [L, shaggy hair, tuft of hair, var. of vellus, a fleece, WOOL] 1. Anat. any of numerous hairlike or fingerlike vascular processes on certain mucous membranes of the body, as of the small intestine, serving to… …   English World dictionary

  • villus — 1. A projection from the surface, especially of a mucous membrane. If the projection is minute, as from a cell surface, it is termed a microvillus. 2. An elongated dermal papilla projecting into an intraepidermal …   Medical dictionary

  • villus — n.; pl. villi one of many short finger like processes that project from some membranous surfaces. Numerous intestinal villi line the small intestine. Each contains a network of blood capillaries and a lacteal. Their function is to absorb the… …   The new mediacal dictionary

  • villus — UK [ˈvɪlʌs] / US noun [countable] Word forms villus : singular villus plural villi UK [ˈvɪlaɪ] / US biology 1) one of a large number of small parts that stick out from the inner wall of the small intestine 2) a part like a hair that grows on a… …   English dictionary

  • Villus, S. — S. Villus soll nach Migne zu Madrid in Verehrung stehen …   Vollständiges Heiligen-Lexikon

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