1. Genitourinary System

2. Functions of the Kidney Excretion – Removal from the body of the waste products of metabolic pathways Osmoregulation – Is the control of the water balance of the blood, tissue, or cytoplasm of a living organism.

3. Kidney Structure

4. Nephron – the functional unit of the kidney

5. Ultrafiltration in the glomerulus

6. Ultrafiltration specifics Production of filtrate from blood 20% of blood plasma passes through walls of glomerulus; higher than any other cap. bed. Why? 1. bp is very high due to diameter differences of the efferent and afferent arterioles 2. glomerular capillaries are fenestrated Pores large : all substances can pass through But basement membrane acts as a filter

7. The Urinary System Plasma, Filtrate, and Urine ComparisonsTable. Average Composition of Blood Plasma, Glomerular Filtrate, and Urine Blood PlasmaGlomerular FiltrateUrine Substance (total amount)(amount per day) (amount per day) Water 3 L 180 L 1-2 L Urea 4.8 g 53 g 25.0 g Chloride 10.7 g 639 g 6.3 g Sodium 9.7 g 580 g 4.6 g Potassium 0.5 g 30 g 2.0 g Creatinine 0.03 g 1.6 g 1.6 g Uric acid 0.15 g 8.5 g 0.8 g Protein 200.0 g 2.0 g 0.1 g Bicarbonate 4.6 g 275.0 g 0.0 g Glucose 3.0 g 180.0 g 0.0 g

8. Selective Reabsorption in the PCT Filtrate at this point contains waste and substances the body needs PCT consists of a single layer of cuboidal epithelial cells with microvilli = increased SA

9. PCT cont’d IMPs all cell over surfaces for AT Mitochondria in large numbers producing ATP to drive AT

10. What’s Re-absorbed? 100% of glucose 80% of mineral ions (including Na) AT of solutes makes cell hypertonic which cause water to follow. 80% of water is re-absorbed; 20% of water remains in the renal tubule and heads towards the LOH

11. Role of the LOH Descending and acsending limbs differ in permeability. Major role? To create an area of high solute conc. in the medulla (hypertonic interstitial fluid)

12. Osmoregulation in the CD Water conc. in blood too low = ADH release from pituitary gland in brain = Increase in aquaporin production in CD cells CD passes through zone of high solute conc created earlier by the LOH Hypertonic urine is produced

13. If water conc in blood is too high (hypotonic blood) = ADH is not secreted = Aquaporins are broken down = CD becomes less permeable to water Dilute, hypotonic urine is produced