Dept. of Physiology. ZJU School of Medicine.

Transcription

1 Urinary System Dr. ZHANG Xiong Dept. of Physiology ZJU School of Medicine =view&coursetype=0&courseid=26519 QUESTION 6 How is the filtrate reabsorbed in tubular system? stem? 1

2 Composition of extracellular fluid compartment: Water, proteins, glucose, amino acids, electrolytes (Na +, K +, Ca 2+, Cl -, HCO - 3, Pi), urea and uric acids Composition of renal filtrate in proximal tubules: Water, glucose, amino acids, electrolytes (Na +, K +, Ca 2+, Cl -, HCO 3-, Pi), urea and uric acids Urine: Water, electrolytes l t (Na +, K +, Ca 2+, Cl -, HCO 3-, Pi), urea and uric acids 2

3 Ways with which h the kidney reabsorbs a substance Pathways which h the substances are reabsorbed Paracellular path Transcellular path Active reabsorption Passive reabsorption 3

4 Reabsorption in proximal tubule: Na +, glucose, Amino Acids, bicarbonate, Cl -, water. Reabsorption in thin Henle s loop: Only water is allowed dto reabsorbed b in thin descending limb and Na + is reabsorbed in thin ascending limb. Reabsorption in thick ascending limb of Henle s loop: Na +, K +, Cl - (in the ratio 1:1:2) are actively transported by Na + /K + /Cl - cotransporter. Reabsorption in distal convoluted tubule and collecting duct: Reabsorption of Na + is regulated by aldosterone. Reabsorption of water is regulated by antidiuretic hormone(adh). Reabsorption of sodium ion Co-transport: Na + glucose and Na + amino acids symport Counter-transport: Na + H + antiport 4

5 Co-transport of Glucose or amino acids with sodium ion Glucose threshold diabetes mellitus Reabsorption of bicarbonate It is important to keep acid-base balance. Per ritubu ular capil lary 5

6 Reabsorption of water diffuse through tight junction between the adjacent tubule cells Reabsorption of Chloride Ion Passive reabsorption: With water is reabsorbed, the concentration of Cl - in filtrate is increased and produces a concentration-drived ed diffusion. More Na + than substances with negative charge is reabsorbed and produced a potential-drived ti di ddiffusion. i The main pathway is paracellular pathway. 6

7 QUESTION 7 How to keep acid-base balance in body by kidney? Our body is an acid producer 1. Volatile acid CO +H = ~ 000mM O H 2 CO 3 10,000mM of H 2. Non-volatile or fixed acid mm H + H 3PO 4 - breakdown product of phosphoprotein, p p phospholipid, phosphoglyceride & cysteine H 2 SO 4 - breakdown product of methionine and cysteine 7

8 Conseqences of acid-base imbalance Acidosis (ph < 7.4) : depression of CNS disorientation coma death Alkalosis (ph > 7.4) : hyper-excitability excitability of nerve and muscle convulsion tetany Responses to acid-base disturbance 1. Buffer system in blood plasma H + + HCO 3- = H 2 CO 3 The most important buffer in the body 2. Respiratory defense 3. Renal defense Secretion of H + and Reabsorption of HCO 3 - Secretion of NH 3 and Production of NH + 4 Secretion of H + and HPO / H 2 PO 4 buffer 8

9 Secretion of H + and Reabsorption of HCO 3 - Na + H + exchanger in proximal and distal tubule Intercalated cell in late distal and collecting tubules: H + -ATPase Secretion of NH 3 and Production of NH 4 + Proximal ltubule Distal tubule Glutamine 9

10 Acidosis and hyperkalaemia In the distal tubule: Secretion of K + by Na + K + exchange is compete with secretion of H +. Acidosis enhances the secretion of H + and inhibits secretion of K +, to cause hyperkalaemia. H + Secretion of H + and dhpo 2-4 /HPO 2 4- buffer 10

11 Tubular Secretion of Other Substances Para-aminohippuric aminohippuric acid (PAH) Some foreign substances, such as penicillin and phenol red. 11

12 References 1. Guyton and Hall Textbook of Medical Physiology 10th Edition 2. Datta, Mirpuri and Patel Crash Course Renal and urinary Systems, 2nd edition 3. Vander s Human Physiology h 10 th Edition Thank you! 12