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http://www.youtube.com/watch?v=hXysuAt_U9s Excretion removal of metabolic waste Protein and nucleic acid metabolism nitrogen containing compounds does not include feces Excretion is an example of homeostasis Prevent build up of toxic wastes within our body Contribute to water balance in our body Organs Responsible for Excretion Composition of Urine solution of metabolic waste Water (mostly) urea and uric acid salts organic compounds Compounds within asparagus are metabolized Produce a byproducts that contain sulfur fluid for urine comes from filtered blood extracellular fluid (ECF) Forms of Nitrogenous Waste Urea Ammonia Uric Acid deamination – removal of amine group Occurs in the liver Byproducts are sent to the kidneys for further processing Urea product of two other waste molecules ammonia, NH3 (very toxic) carbon dioxide, CO2 Ammonia ammonia released when liver breaks down proteins 0.005 mg NH3 is lethal reacts with CO2 to produce less toxic urea 100 000x less toxic than NH3 Uric Acid product of nucleic acid breakdown specifically of purine bases Role of Kidneys 1. Removal of wastes Urea, uric acid and other materials are filtered through the kidney and excreted 2. Water balance average person loses 2L of liquids a day suggested to consume 2L H2O / day Excretion: Ameoba Ameoba remove waste and excess water through a contractile vacuole. Excretion: Fish Fish can excrete ammonia directly through their gills. Excretion: Birds Birds excrete uric acid directly with feces. Excretion: Earthworms capillary network bladder collection tubule nephrostome nephridiopore AKA The Kidney Role of Kidney 1. 2. 3. 4. 5. blood filtration waste excretion acid / base balance blood pressure regulation hormone secretion Kidney Structure renal cortex – outside of kidney; location of Bowman’s capsule renal medulla (lobes) – middle of kidney; location of loop of Henle renal pelvis – location of the ends of collecting ducts Kidney Blood Flow Blood enters the kidney through the renal artery. renal arteries stem from the aorta Carry oxygenated blood Filtered blood exits the kidney through the renal vein. renal veins flow into the inferior vena cava Carry de-oxygenated blood Nephron Functional unit of the kidney Responsible for the formation of urine A million nephrons make up the kidney Blood and the Nephron Blood from renal artery is filtered through nephrons. Nephrons collect liquid to be excreted Filtered blood is returned to renal vein Renal artery The renal artery is split into afferent arterioles. blood brought to glomerulus; a capillary bed. blood leaves through the efferent arterioles no veins involved Efferent arterioles are the beginning of a network of peritubular capillaries, that wrap around the nephron. Glomerulus and Bowman’s Capsule Efferent Arteriole Afferent Arteriole Filtrate From the bowman’s capsule: fluids to become urine flow to narrow proximal tubule urine flows through loop of Henle urine flows through distal tubule Urine from multiple nephrons flow into the collecting duct. Urine Flow Urine leaves the renal pelvis through the ureters and travels to the bladder. Fluid leaves the body through the urethra. When ~200 mL of urine has collected in the bladder, the walls stretch and signals are sent to the brain. At ~600 mL, urine will involuntarily be released. ureters Nephron Structure efferent arteriole proximal tubule glomerulus Bowman’s capsule distal tubule collucting duct afferent arteriole Loop of Henle Urinary System aorta inferior vena cava renal cortex renal medulla renal artery renal vein kidney ureter bladder renal pelvis nephrons urethra ureter Question Athletes now undergo random urine testing for drugs. Describe the pathway of drugs through the urinary system, from the time they enter the glomerulus until they are excreted in the urine. Homework Quiz Question 1 Homework Quiz Question 2 You are sick and take an antibiotic. Describe the pathway of the drug through the urinary system, starting from the aorta to the toilet! Passive transport. Substances move spontaneously down their concentration gradients, crossing a membrane with no expenditure of energy by the cell. The rate of diffusion can be greatly increased by transport proteins in the membrane. Active transport. Some transport proteins act as pumps, moving substances across a membrane against their concentration gradients. Energy for this work is usually supplied by ATP. ATP Diffusion. Hydrophobic molecules and (at a slow rate) very small uncharged polar molecules can diffuse through the lipid bilayer. Facilitated diffusion. Many hydrophilic substances diffuse through membranes with the assistance of transport proteins, either channel or carrier proteins. Three Functions of Urine Formation 1. 3. Capillary 1 Excretory tubule Filtration. Filtrate 2. Filtration – movement of fluids from the blood in the glomerulus to the Bowman’s capsule Reabsorption – transfer of fluids from nephron into peritubular capillaries Reabsorption. 3 Secretion. interstitial fluid Urine Secretion – transfer of fluids from peritubular capillaries into nephron 2 4 Excretion. Filtration Water and solutes flow from 1 Excretory tubule Filtration. Filtrate the glomerulus into Bowman’s capsule due to high blood pressure flow Capillary 65 mmHg vs. normall ~ 25 2 Reabsorption. mmHg 3 Secretion. Urine Semi-permeable membrane Red blood cells, platelettes and some blood proteins are too large to fit through the filtration slits and pores. 4 Excretion. Nutrient Flow Solute Glomerulus Bowman’s Capsule? water NaCl H+ ions yes yes yes amino acids glucose yes yes plasma proteins no red blood cells (erythrocytes) no platelets no Reabsorption Capillary 1 Reabsorption reclaims Filtration. Filtrate Excretory tubule valuable substances from the filtrate and returns them to the body fluids. Water, salt and nutrients saves us from having to Reabsorption 3 Secretion. 20% of fluid flowing into kidney is filtered into nephrons; however less than 1% of the fluid in the nephron is used to 4 Excretion. make urine. Urine continuously replenish our body with fluid. 2 A LOT OF REABSORPTION! Secretion Capillary 1 Filtration. Filtrate Other substances are Excretory tubule extracted from body fluids and added to the contents of the nephron 2 Reabsorption. toxins and excess ions 3 Secretion. Urine 4 Excretion. Capillary 1 Reabsorption Filtration. Filtrate Excretory tubule protein transporters Secretion. 4 Excretion. Secretion protein transporters move Diffusion. Hydrophobic wastes from blood to interstitial fluid to nephron molecules and (at a slow rate) very small uncharged polar molecules can diffuse through the lipid bilayer. Reabsorption. 3 Urine move nutrients into interstitial fluid and blood kidney tissue will only reabsorb a certain level of nutrients – threshold level 2 Facilitated diffusion. Many hydrophilic substances diffuse through membranes with the assistance of transport proteins, either channel or carrier proteins. ATP The Details… 1. Bowman’s Capsule High pressure filter water and dissolved solutes leave glomerulus; enter Bowman’s capsule water Na+ H+ Clglucose amino acids vitamins minerals urea uric acid 2. Proximal Tubule HCO3-, K+ Na+, ClH2O amino acids glucose vitamins Selective reabsorption of nutrients (need transporters) Secretion of H+ and ammonia pH determined by HCO3- reabsorption and H+ secretion H+ NH3 3. Loop of Henle – Descending Limb Nephron membrane only permeable to H2O (osmosis) and impermeable to salt Reabsorption of water As fluids travel down the loop of henle, the fluids within the tube become more concentrated. H2O 4. Loop of Henle – Ascending Limb only permeable to salt (need ionic transporters) and not permeable to water Reabsorption of salt As fluids travel up the loop of henle the fluid is becoming less concentrated NaCl 5. Distal Tubule HCO3Na+, ClH2O Selective reabsorption of nutrients (need transporters) Secretion of H+, ammonia and K+ pH determined by HCO3- reabsorption and H+ secretion H+ NH3 K+ 6. Collecting Duct Urine formation by concentration of nephron fluid Any urea and urine that is reabsorbed is less than that was filtered into nephron Why is some urea reabsorbed? Contributes to the formation of a hypertonic interstitial fluid causes water to be reabsorbed CONCENTRATING THE URINE NaCl urea water 1 Proximal tubule NaCl HCO3 Nutrients H2O K+ H+ NH3 4 Distal tubule H2O NaCl HCO3 K+ H+ CORTEX 2 Descending limb of loop of Henle Filtrate H2O Salts (NaCl and others) HCO3– H+ Urea Glucose; amino acids Some drugs 3 Thick segment of ascending limb NaCl H2O OUTER MEDULLA NaCl 3 Thin segment of ascending limb Key Urea NaCl Active transport Passive transport 5 Collecting duct INNER MEDULLA H2O Osmolarity of interstitial fluid (mosm/L) 300 300 100 300 100 CORTEX NaCl H2O Active transport 200 400 300 300 400 400 600 600 H2O H2O NaCl H2O H2O NaCl H2O Passive transport OUTER MEDULLA NaCl H2O 400 600 H2O NaCl H2O NaCl H2O H2O Urea 700 900 INNER MEDULLA H2O NaCl 900 H2O Urea H2O 1200 Urea 1200 1200 Osmolarity – concentration of solutes in a solution, the higher the Osmolarity, the more concentrated the solution, the better it is able to pull water towards it. http://www.biologymad.com/resources/kidney.swf Diabetes (Type II) Not enough insulin released from pancrease High levels of glucose in the blood Why do you think that individuals with Type II Diabetes (untreated) (a) Excrete a large amount of gluose in the urine? (b) Excrete large amounts of urine? Kidney Stones crystallization of some urine solutes a 2 – 3 mm stone can obstruct flow to the ureter Treatment: increased water consumption surgery Homework/Classwork 7.3 – Pg. 345 #1-4,6 7.4 – Pg. 348 #1-3 7.5 – Pg. 352 #2-8 Homework Quiz next class!