11 05 07 Osmoregulation and the Excretory System

11 05 07 Osmoregulation and the Excretory System - Chapter...

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Chapter 20 – The Excretory System and Osmoregulation Intermediate mesoderm- gives rise to the excretory and urogenital system Located in dorsolateral coelem The kidneys are the primary excretory organs of the vertebrate body - eliminate wastes and toxins, water, salts Generalized Structure Kidneys are made of 2 parts, which are separated in early vertebrates but continuous in others: the glomerulus filters blood producing filtrate, and the nephric (renal) tubules collect filtrate. - Filtrate is modified by reabsorption or secretion - Excretory system second system to form - Glomerulus= capillary Plasma= liquid part of blood, not cells These two components make up a nephron , a single functional unit of urine formation. Functional unit of the kidneys Urine is collected from the nephric tubules into a pair of nephric ducts that carry it to the cloaca (or bladder) Found on either side of the body and it is segmented The glomerulus is surrounded by 2 layers of the nephric tubule, called the renal capsule - 1 layer lies on top of, and surrounding the glomerulus - podocytes - the 2 nd layer surrounds the glomerulus and the podocytes - the space between the 2 layers receives filtrate from the plasma and is continuous with the lumen of the nephric tubule Development of the kidneys Development is an example of Haeckel’s principle, “ontogeny recapitulates (is a reflection of) phylogeny” A series of progressively more advanced kidneys develop over the course of development 3 parts of kidneys of vertebrate embryos: a. Pronephros : Anteriorly, in a position dorsal to the heart, the paired intermediate mesoderm begins to segment, forming the pronephros. The tubules fuse at their ends and form a pronephric
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This note was uploaded on 08/16/2008 for the course BIOL 276 taught by Professor Johnson during the Spring '07 term at UNC.

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11 05 07 Osmoregulation and the Excretory System - Chapter...

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