nephridium
nephridial, adj.
/neuh frid"ee euhm/, n., pl. nephridia /-frid"ee euh/. Zool.
the excretory organ of many invertebrates, consisting of a tubule with one end opening into the body cavity and the other opening into a pore at the body surface.
[1875-80; < NL; see NEPHR-, -IDIUM]

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      unit of the excretory system in many primitive invertebrates and also in the amphioxus; it expels wastes from the body cavity to the (usually aquatic) exterior. The evolution of nephridia encouraged tissue specialization by eliminating the need for all cells of an organism to be in contact with seawater for diffusion of metabolic wastes.

      Nephridia occur in two forms. The simpler, more primitive protonephridia, found in flatworms, ribbon worms, and rotifers, are usually scattered among the other body cells. More advanced, segmented invertebrates, such as earthworms, possess the more complex metanephridia, usually arranged in pairs.

      The protonephridium consists of a hollow cell located in the body cavity and a duct leading from it to an exterior opening, called a nephridiopore. Fluid in the body cavity filters into the hollow cell, called a flame bulb (or flame cell) if it possesses cilia, or a solenocyte if it has a flagellum. In either form, the cilia or the flagellum wave filtered urine down the tube to the outside.

      The metanephridium tubule lacks a flame cell and opens directly into the body cavity. Cilia lining the tubule draw up cavity fluids and conduct them to the exterior; tubule cells actively reabsorb useful nutrients as they pass. Analogous structures, the renette and the lateral canal are characteristic of nematodes.

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Universalium. 2010.

Look at other dictionaries:

  • Nephridium — Ne*phrid i*um, n.; pl. {Nephridia}. [NL., fr. Gr. ? of the kidneys.] (Zo[ o]l. & Anat.) A segmental tubule; one of the tubules of the primitive urinogenital organs; a segmental organ. See Illust. under {Loeven s larva}. [1913 Webster] …   The Collaborative International Dictionary of English

  • nephridium — (n.) (pl. nephridia), 1877, Modern Latin, from Greek dim. of nephros kidney (see NEPHRON (Cf. nephron)) …   Etymology dictionary

  • nephridium — [nə frid′ē əm] n. pl. nephridia [nē frid′ēə, ni frid′ēə, ne frid′ēə] [ModL < Gr nephridion, dim. of nephros, kidney: see NEPHRO ] 1. a waste discharging tubule with an external excretory pore, found in many invertebrates, as in worms, mollusks …   English World dictionary

  • Nephridium — A Nephridium (plural nephridia) is an invertebrate organ which occurs in pairs and function similar to kidneys. Nephridia remove metabolic wastes from an animal s body. They are present in many different invertebrate lines. There are two basic… …   Wikipedia

  • Nephridium — Als Nephridium (gr. nephros – Niere) bezeichnet man ein Organ zur Ausscheidung giftiger Abbauprodukte. Im Tierreich gibt es mehrere Typen von Nephridien: Protonephridien: Sie sind die einfachsten Ausscheidungsorgane und kommen hauptsächlich bei… …   Deutsch Wikipedia

  • nephridium — noun (plural nephridia) Etymology: New Latin Date: 1877 a tubular glandular excretory organ characteristic of various invertebrates • nephridial adjective …   New Collegiate Dictionary

  • nephridium — small excretory organs with flame cells found in invertebrates and Amphioxi …   Dictionary of ichthyology

  • nephridium — n.; pl. ia [Gr. dim. nephros, kidney; L. ium, nature of] 1. In various invertebrates, simple or branched, tubular structures that function in excretion, opening to the outside through a nephridiopore; see protonephridium, metanephridium. 2.… …   Dictionary of invertebrate zoology

  • nephridium — noun a) A tubular excretory organ in some invertebrates b) The embryonic excretory organ that developes into the kidney …   Wiktionary

  • nephridium — One of the paired, segmentally arranged excretory tubules of invertebrates such as the annelids. [G. nephros, kidney, + Mod. L. idium, dim. suffix, fr. G. idion] * * * ne·phrid·i·um ni frid ē əm n, pl ia ē ə an excretory organ that is… …   Medical dictionary

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