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Excretory System! New Song! https://www.youtube.com/watch?v=K3Z-Lt58H0s Homeostasis Excretory system maintains homeostasis by balancing the amount of water, salt, and metabolite concentrations within the blood. Not just the Kidney’s! Lungs: Remove CO2 Skin: Removes heat Liver: Removes metabolic wastes and creates bile and urea Kidney: Removes metabolic wastes Mammalian Kidney inferior vena cava aorta adrenal gland kidney nephron ureter bladder urethra renal vein & artery microvilli on epithelial cells http://handsonscience.jimdo.com/online-games-andactivities/unit-4-breathing-circulation-and-excretion/ Mastering biology http://www.youtube.com/watch?v=8UVlXX-9x7Q Mammalian System blood filtrate Filter solutes out of blood & reabsorb H2O + desirable solutes Key functions filtration fluids (water & solutes) filtered out of blood reabsorption selectively reabsorb (diffusion) needed water + solutes back to blood secretion pump out any other unwanted solutes to urine excretion expel concentrated urine (N waste + solutes + toxins) from body concentrated urine Nephron Functional units of kidney 1 million nephrons per kidney Function filter out urea & other solutes (salt, sugar…) blood plasma filtered into nephron high pressure flow selective reabsorption of valuable solutes & H2O back into bloodstream greater flexibility & control why selective reabsorption & not selective filtration? “counter current exchange system” How can different sections allow the diffusion of different molecules? Mammalian kidney Interaction of circulatory & excretory systems Circulatory system Bowman’s glomerulus = ball of capillaries capsule Proximal tubule Distal tubule Glomerulus Excretory system nephron Bowman’s capsule loop of Henle proximal tubule descending limb ascending limb distal tubule collecting duct Glucose Amino acids H2O Mg++ Ca++ H2O Na+ ClH2O H2O Na+ Cl- H2O H2O Loop of Henle Collecting duct Nephron: Filtration At glomerulus filtered out of blood H2O & solutes H2O glucose salts / ions (Na+ / Cl–) urea not filtered out cells & large molecules cells proteins high blood pressure in kidneys force to push (filter) H2O & solutes out of blood vessel BIG problems when you start out with high blood pressure in system hypertension = kidney damage Nephron: Re-absorption Proximal tubule reabsorbed back into blood NaCl active transport of Na+ Cl– follows by diffusion H2O glucose HCO3- bicarbonate buffer for blood pH Nephron: Re-absorption Loop of Henle descending limb reabsorbed H2O structure many aquaporins in cell membranes high permeability to H2O no Na+ or Cl– channels impermeable to salt structure fits function! Nephron: Re-absorption Loop of Henle ascending limb reabsorbed Na+ & Cl– structure many Na+ / Cl– channels in cell membranes high permeability to Na+ & Cl– no aquaporins impermeable to H2O structure fits function! Nephron: Re-absorption Distal tubule reabsorbed salts H2 O bicarbonate HCO3 regulate blood pH Nephron: Reabsorption & Excretion Collecting duct reabsorbed H2O = through aquaporins excretion concentrated urine to bladder impermeable lining = no channels in cell membranes Osmotic control in nephron How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion use diffusion instead of active transport wherever possible the value of a counter current exchange system why selective reabsorption & not selective filtration? Summary Not filtered out of blood cells proteins remain in blood (too big) Reabsorbed back to blood: active transport Na+ glucose amino acids Reabsorbed back to blood: diffusion H2O Cl– Excreted out of body urea excess H2O excess solutes (glucose, salts) toxins, drugs, “unknowns”