Osmoregulation Animal Renal Systems Animal Renal Systems Water Solute Osmosis Osmotic pressure of the solution Water movement Selectively permeable membrane A selectively permeable membrane allows movement of water but not solutes Water moves by osmosis from a region of lower to higher solute concentration Net movement of water stops when osmotic pressure equals hydrostatic pressure due to gravity Water moves by osmosis from a region of lower to higher solute concentration A selectively permeable membrane allows movement of water but not solutes Net movement of water stops when osmotic pressure equals hydrostatic pressure due to gravity Osmoregulation Water Homeostasis Osmoregulation in animals Maintain constant osmotic pressure via Water Drink CLEAN water Food has water Cellular respiration Lost via sweat urine Electrolytes NaCl Diet Lost via sweat Lost via urination defecation Excretion Elimination of Water Soluble Waste toxins Kidneys osmoregulate and eliminate water soluble waste Amphibian Freshwater fish Bird Human Kidney Reptile Blood flow Flow of filtrate Excretory tubule Urine Filtration Reabsorption and Secretion Capillary Filtration produces a filtrate of the blood Reabsorption removes useful solutes from the filtrate and returns them to the blood 1 2 1 3 Secretion adds solutes to the filtrate Filtration produces a filtrate of the blood Reabsorption removes useful solutes from the filtrate and returns them to the blood Secretion adds solutes to the filtrate Vertebrate Kidney and Nephron Kidney Ureter Bladder Glomerulus Filtrate Collectin g duct Tubule Nephron Mammalian Nephron Nephron Glomerulus Peritubular capillaries Vasa recta Renal cortex Renal medulla To renal pelvis Collecting duct Mammalian Glomerulus and Bowman s Capsule Blood is filtered under pressure into the extracellular space formed by Bowman s capsule through a filtration barrier Nephrons Capillary endothelial cell Podocyte Filtration slit Glomerulus Podocyte Movement of filtrate Tubule Fenestra Blood flow Afferent arteriole Efferent arteriole Basal lamina Bowman s space Bowman s capsule Blood is filtered under pressure into the extracellular space formed by Bowman s capsule through a filtration barrier Proximal convoluted tubule Distal convoluted tubule Loop of Henle Collecting duct Renal pyramid Ureter Renal Tubules and Collecting Duct Cortex Medulla Kidney Na K pump Active transport in the proximal tubule Loop of Henle Functions Reabsorb water Descending limb only permeable to water water limb and urea Water can not be actively pumped out Makes the medulla hypertonic Ascending limb actively pumps salts Na K Cl salty limb creating a concentration gradient Medulla is hypertonic to the filtrate facilitating water reabsorption 300 300 300 100 100 CORTEX 400 200 H2O H2O H2O H2O H2O H2O H2O NaCl NaCl NaCl NaCl NaCl NaCl NaCl 1 200 OUTER MEDULLA 600 400 900 700 Key Active transport Passive transport INNER MEDULLA Osmolarity of interstitial fluid mOsm L 300 400 600 900 1 200 Urea Recycling Urea is water soluble hydrophilic and small Can diffuse across a lipid bilayer barely Urea transport proteins facilitated diffusion upregulated in response to ADH Urea can also cross via SOME aquaporins Desc limb is permeable to urea Asc limb is NOT permeable Collecting duct is always permeable but more so when ADH is present 300 300 300 100 100 Osmolarity of interstitial fluid mOsm L 300 300 CORTEX 400 200 400 400 H2O H2O H2O H2O H2O H2O H2O NaCl NaCl NaCl NaCl NaCl NaCl NaCl 1 200 H2O H2O NaCl H2O NaCl H2O H2O Urea H2O Urea H2O Urea OUTER MEDULLA 600 400 600 600 Key Active transport Passive transport INNER MEDULLA 900 700 900 1 200 1 200 Hormonal Control of Urine Concentration Collecting duct Collecting duct Cortex Cortex Outer medulla Outer medulla ADH H2O H2O ADH H2O ADH H2O ADH H2O ADH H2O H2O ADH ADH ADH H2O H2O H2O Inner medulla Inner medulla Concentrated urine Dilute urine ADH released from the posterior pituitary gland increases the collecting ducts permeability to water allowing water to diffuse out of the filtrate with the gradient created by the loop of Henle In the absence of ADH the collecting duct is less permeable to water resulting in dilute urine In the absence of ADH the collecting duct is less permeable to water resulting in dilute urine ADH released from the posterior pituitary gland increases the collecting ducts permeability to water allowing water to diffuse out of the filtrate with the gradient created by the loop of Henle Transmembrane protein Impermeable to ion flow sometimes 13 unique AQPs discovered in humans so far AQ 1 3 4 7 have been found in the nephron 3 4 and 7 allow urea to pass Aquaporins AQP when Osmosis alone just won t do Giant Kangaroo Rat Animal Physiology Recap The body s solutions to all of multicellularity s problems via homeostasis neg feedback Communicating quickly Sensing understanding and responding Delivering and removing Acquiring energy and nutrients Osmoregulating and Detoxifying Form vs Function Be curious Trust skeptical Use your platform Hydrate Sleep Thank you Lecture Learning Objectives 1 Know why renal organs eliminate nitrogenous wastes and regulate water and electrolyte levels 2 Understand the role of the Glomerulus how it filters and what comes through 3 Explain the role of the convoluted tubules what comes out and what stays in the filtrate 4 Analyze the loop of Henle in the nephron and understand how water NaCl are retained via the countercurrent structure 5 Know where urea recycling occurs and why it is necessary 6 Know when how antidiuretic hormone and aquaporins are employed to save water and create concentrated urine