Salt gland

Salt gland

The salt gland is an organ for excreting excess salt. It is found in elasmobranchs, marine birds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in the skull, in the area of the eyes or nostrils. Such glands work by active transport via sodium-potassium pump that moves salt from the blood into the gland, where it can be excreted as a concentrated solution. Salt glands function to keep salt balance, and allow marine reptiles to drink seawater.cite web |url=http://www.cartage.org.lb/en/themes/sciences/Zoology/AnimalPhysiology/Osmoregulation/Osmoregulation.htm |title=Osmoregulation and Excretion |accessdate=2007-07-06 |last=O’Driscoll |first=K.J. |coauthors=Staniels, L.K.; and Facey, D.E. ]

The need for salt glands in reptiles and birds stems from the fact that their kidneys are much less efficient than those of mammals. Unlike the skin of amphibians, reptile and bird skin is impermeable to salt, meaning that the transition to a tougher skin meant a loss in salt-releasing ability. The evolution of a salt gland would have allowed early reptiles and birds to eat aquatic plants and animals, who have high salt concentrations. This does not, however, explain the evolution of the gland in the elasmobranchs, suggesting convergent evolution.

Some theories suggest that mammalian tear ducts and sweat glands may be evolutionarily related to salt glands. Human tears are high in potassium, lending support to this theory, however most phylogenists disagree with this idea.

External links

* [http://www.aquaticape.org/saltglands.html Salt Glands]

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • salt gland — salt′ gland n. anat. zool. one of a pair of glands located near the eyes of seabirds and various marine mammals and reptiles that secretes excess salt imbibed or ingested • Etymology: 1945–50 …   From formal English to slang

  • salt gland — a gland, located in the head of seabirds and various marine mammals and reptiles, that secretes into the nasal passages the excess salt imbibed or ingested. [1945 50] * * * salt gland, a gland found in various animals, especially aquatic birds,… …   Useful english dictionary

  • salt gland — noun a specialized gland, located near the eyes or nose of certain marine animals that secretes a liquid having a high salt content; it enables the animal to drink seawater without having to eliminate the excess salt through the kidneys …   Wiktionary

  • salt gland — noun Date: 1950 a gland (as of a marine bird or a plant) capable of excreting a concentrated salt solution …   New Collegiate Dictionary

  • salt gland — a gland, located in the head of seabirds and various marine mammals and reptiles, that secretes into the nasal passages the excess salt imbibed or ingested. [1945 50] * * * …   Universalium

  • Salt — This article is about common table salt. For other uses, see Salt (disambiguation). Table salt (NaCl) crystal …   Wikipedia

  • salt — salt1 saltlike, adj. /sawlt/, n. 1. a crystalline compound, sodium chloride, NaCl, occurring as a mineral, a constituent of seawater, etc., and used for seasoning food, as a preservative, etc. 2. table salt mixed with a particular herb or… …   Universalium

  • SALT — /sawlt/, n. See Strategic Arms Limitation Talks. * * * I Chemical compound formed when the hydrogen of an acid is replaced by a metal or its equivalent, such as ammonium (NH4). Typically, an acid and a base react to form a salt and water. Most… …   Universalium

  • Gland, thyroid — The thyroid gland is located in the lower part of the neck below the Adam s apple. It is wrapped around the windpipe (the trachea) and has the shape of a butterfly, since it is formed by two wings (lobes) which are attached by a middle part.… …   Medical dictionary

  • Supraorbital gland — The supraorbital gland is a type of lateral nasal gland found in some species of marine birds, particularly penguins, which removes sodium chloride from the bloodstream. The gland s function is similar to that of the kidneys, though it is much… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”