Three Functions of Urine Formation • Filtration – movement of fluids from the glomerular blood to the Bowman’s capsule • Reabsorption – transfer of fluids from nephron back into peritubular capillaries • Secretion – transfer of fluids peritubular capillaries into nephron

Filtration Nutrients flow from glomerulus into Bowman’s capsule due to high blood pressure flow (of the artery)

Nutrient Flow of the following nutrients, which ones will flow out of the blood into the filtrate? Solute Glomerulus  Bowman’s Capsule? water NaCl H+ ions amino acids glucose plasma proteins red blood cells (erythrocytes) platelets

Reabsorption Reabsorption saves us from having to continuously replenish our body with fluid. 20% of fluid flowing into kidney is filtered into nephrons less than 1% of nephron fluid is used to make urine

Reabsorption vs. Secretion carrier/channel proteins move nutrients into interstitial fluid and then back into blood kidney tissue will only reabsorb a certain level of nutrients carrier/channel proteins move wastes from blood to interstitial fluid to nephron

1. Bowman’s Capsule water and dissolved solutes leave glomerulus; enter Bowman’s capsule water Na+ H+ Cl- glucose amino acids vitamins minerals urea uric acid

selective reabsorption of nutrients (need transporters) 2. Proximal Tubule HCO3-, K+ Na+, Cl- H2O amino acids glucose vitamins selective reabsorption of nutrients (need transporters) Urine pH determined by HCO3- reabsorption and H+ secretion H+ NH3

3. Loop of Henle – Descending Limb only permeable to H2O (osmosis) impermeable to salt solutions in tube are being concentrated H2O

4. Loop of Henle – Ascending Limb only permeable to salt (need ionic transporters) impermeable to water NaCl

5. Distal Tubule selective reabsorption of nutrients (need transporters) urine pH determined by HCO3- reabsorption and H+ secretion HCO3- Na+, Cl- H2O H+ K+

6. Collecting Duct urine formation by concentration nephron fluid any urea and urine that is reabsorbed is less than that was filtered into nephron NaCl urea water

Kidney Stones crystallization of some urine solutes a 2 – 3 mm stone can obstruct flow to the ureter Treatment: increased water consumption surgery

HOMEWORK Practice Pg 454 #3,10 Pg 461 #32,33,34 Pg 462 # 54, 57