Transcript Slide 1
Excretory: Disposal & Osmoregulation Excretion: Disposal of nitrogen-containing wastes Osmoregulation: Control of gain and loss of water and solutes Osmoregulation based largely on regulating solutes Water follows the movement of solutes by osmosis Excretion: Aquatic Animals Animals must dispose of nitrogenous waste Metabolism produces nitrogenous wastes from breakdown of proteins and nucleic acids Most aquatic animals dispose of their nitrogenous wastes as ammonia Highly soluble in water Diffuses rapidly across cell membranes Excretory: Saltwater Fish Excretion: Land Animals Land animals convert ammonia to less toxic compounds Can be safely stored and transported in the body Released periodically by excretory system Requires energy for conversion Different adaptations and type of reproduction determine excretion as urea or uric acid Excretory: Disposal & Osmoregulation Urea Excreted by mammals, most amphibians, sharks, and some bony fishes Can be stored in concentrated solution but requires water for disposal Uric acid Excreted by birds, reptiles, insects, some amphibians Excreted as solid paste for water conservation Uses more energy for excretion Excretory Excretory: Waste Protein and nucleic acid breakdown nitrogen-containing wastes toxic byproducts of Ammonia poisonous but soluble and easily disposed of Urea less toxic, easy to store and excrete Some land animals save water by excreting a virtually dry waste Excretory: Waste in Urine Urea – from amino acid breakdown Uric Acid – from nucleic acid breakdown Creatinine – muscle metabolism waste product Excretory System The excretory system expels wastes regulates water and salt balance Two human kidneys each contain ~ million nephrons Urine leaves kidneys via ureters Stored in urinary bladder Excretory Systen Bowman’s capsule Arteriole from renal artery Each nephron: folded tubule and associated blood vessels Nephrons extract filtrate from blood Refine filtrate into much smaller amount of urine 1 Proximal tubule Glomerulus Capillaries Arteriole from glomerulus Branch of renal vein 3 Distal tubule From another nephron Collecting duct 2 Loop of Henle with capillary network D. DETAILED STRUCTURE OF A NEPHRON Figure 25.9D LE 25-11 Blood Filtrate composition H2O NaCI HCO3– H+ Urea Glucose Amino acids Some drugs Proximal tubule Bowman’s capsule Nutrients H2O HCO3– NaCI Some H+ drugs and poisons Distal tubule NaCI H2O HCO3– K+ H+ Cortex Collecting duct Medulla Loop of Henle NaCI NaCI H2O Reabsorption Urea Secretion NaCI H2O Urine (to renal pelvis) Excretory: Filtration Filtration (Bowman’s capsule) Blood pressure forces water and many solutes from blood (glomerulus) into nephron Excretory: Reabsorption / Secretion Controlled secretion of H+ and reabsorption of bicarbonate ions help regulate blood pH Secretion also includes active transport of drugs and poisons Reabsorption of salts and urea allow osmotic reabsorption of water Excretion: Reabsorption / Secretion PROXIMAL TUBULE – always reabsorb glucose and amino acid - sometimes water, sodium, potassium, calcium depending on need Secretion urea, creatinine, ions, drugs and toxins Excretory: Reabsorbing Water - - LOOP OF HENLE - much water reabsorbed via active transport of salt salt concentration in kidney higher in medulla Longer loop – more water conservation (desert animals) Excretory: Reabsorption/Secretion - DISTAL TUBULE specialized “Urine fine tuning” Aldosterone hormone – increases amount of sodium reabsorbed into blood (water follows) Excretory: Water Reabsorption in Collecting Duct Water reabsorbed ADH (antidiuretic hormone) – cause collecting walls to be permeable to water to be reabsorbed Caffeine interferes with ADH (dehydration) Excretory: Regulates Blood Pressure Releases RENIN when blood pressure low - enzyme that causes production of chemical (angiotensin II) to constrict blood vessel - Angiotensin II increase aldosterone production Excretory: Dialysis Homeostasis: Liver It assists the kidneys by making urea from ammonia breaking down toxic chemicals Liver Blood from intestines flows through the liver before distribution to the rest of the body Allows liver to adjust blood’s chemical content