MCDB 1B Lecture 6: Excretory Systems
6 Mar 2018
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Characteristics of cells engaged in absorption (high surface area/volume ratio) Blood carries nutrients and waste --> requires filtration to remove garbage. Maintain osmotic balance of cells and ecf to prevent extreme volume changes. Requirements and mechanisms vary depending on animals environment. Live in fresh water - need to excrete water, conserve solutes. Live in terrestrial/dry environment - need to conserve water, excrete solutes. Live in ocean - equilibrate extracellular fluid with ocean (osmoconformers) or conserve water, excrete salts (osmoregulators) Ammonotelic animals (aquatic invertebrates and most boney fishes) The nephron is the functional unit of the vertebrate kidney. Renal tubule - site of tubular secretion and absorption, surrounded by capillaries. An arteriole supplies blood to the glomerulus under pressure. The glomerulus, a knot of capillaries, is the site of blood filtration. An efferent arteriole carries blood from the glomerulus. Renal tubule cells alter composition of glomerular filtrate through reabsorption and secretion of solutes.
