Chapter 44-A Balancing ActOsmoregulation: regulates solute concentrations and balances the gain and loss of waterExcretion: Gets rid of nitrogenous metabolites and other waste products-Concept 44.1 Osmoregulation balances the uptake and loss of water and solutes-Osmosis and OsmolarityOsmolarity: the solute concentrations of a solution determine the movement of water across a selectively permeable membrane.Isosmotic: water is equal in and outHyposmotic: fat with water, less solutes, water flow is outHyperosmotic: Skinny with water, more solutes, water flow is in-Land AnimalsLand animals maintain water balance by eating moist food and producing water metabolically-Concept 44.2: Animal’s nitrogenous wastes reflect its phylogeny and habitatMost animals convert ammonium to less toxic compounds prior to excretion-Forms of Nitrogenous WasteAmmoniaNeed access to lots of waterrelease across whole body or through gillsUreaAmmonia is converted to urea (less toxic)Taken to kidneys where it is excretedUric AcidInsects, snails, reptiles and birdsPaste, wastes little water-Concept 44.3: Diverse excretory systems are variations on a tubular themeExcretory system regulates:1) Water2) Ions3) pH-Excretory ProcessMost excretory systems produce urine by refining a filtrate derived from bodily fluidsKey functions1) Filtration2) Re-absorption of valuable solutes3) Secretion of nonessential solutes and waste from the body fluids tothe filtrate4) Excretion: Processed filtrate (POOP)-KidneysKidneys: Excretory Organs of vertebrates function in both excretion and osmoregulationEach Kidneys is supplied with blood by a renal artery and drained by a renal vein.Urine exits each kidney through a duct called the ureter both ureters drain into a common urinary bladder that stores urine until it is expelled through the urethra-The NephronNephron is the function unit of the vertebrate kidney, it consists of a singlelong tubule (renal tubule) and a ball of capillaries called the glomerulus (capillary network that is branched from the renal artery)Bowman’s capsule is located at the blind end of the renal tubule and surrounds and receives filtrate from the glomerulusRenal tubule extends from the Bowman’s capsule into the proximal tubule, loop of Henle, distal tubule and collecting duct-Urine formation1) Filtration of BloodFiltrate occurs as blood pressure forces fluid from blood in the glomerulus (capillaries) into the lumen of the bowman’s capsuleNon-SelectiveThe filtrate produced in Bowman’s capsule contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small moleculesCells and large molecules (proteins) are unable to pass though the glomerular capillary wall and are not present in filtrate2) Reabsorption Most filtered Water ions , molecules are reabsorbed from the renal tubule back into the peritubular capillariesreabsorption of water ions, all amino acids, and all glucose occurs in the proximal tubuleReabsorption of water occurs in the descending limp of the loop of Henle while absorption of sodium and chloride ions occurs in the ascending limb of the loop of Henle.Reabsorption of water also occurs in the distal tubule and collectingduct. (HCO3- reabsorption in the distal tubule)ADH increases H20 absorption in the distal tubule by increasing aquaporins and concentrate urine3) SecretionToxic substances and excess ions (such as H+, K+) are secreted from the peritubular capillaries into the renal tubuleH+ and NH3 are secreted into the proximal tubuleH+ and K+ are secreted into the distal tubuleControlled movement of H+ ions contributes to pH regulation-Urine TransportSubstances that are not reabsorbed are transported into the collecting ductwhich leads to the interior of the KidneyUrine is hyperosmotic to body fluids (lots of solutes, less water)Leaves Kidneys to the urinary bladder through the ureters, urine is stored in the
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