七年制医学课件 病理生理 4 k.ppt

Disorders of Potassium Metabolism Distribution of potassium between ICF ECF Factors influencing K+ balance in the body losses ICF K+ due to vomiting (150~160 mmol/L) Absorption K+ in foods GI tract Plasma K+ Sweat (100 mmol/d) (5-10 mmol/d) (3.5-5.5 mmol/L) Secretion losses by by ADS from diarrhea alkalosis / acidosis Urinary losses (90--95 mmol/d) K+ Intake Excretion Route of excretion of K+ Kidneys( 90 %), feces sweat. K+ is : a. filtered --- at the glomerulus. b. reabsorbed --- by an active process in the proximal portions c. secreted --- distally appears in the urine Changes in the amount of K+ excreted in the urine are mainly due to changes in the distal K+ secretion. Mechanisms regulated distribution of K+ between ICF ECF ( l ) Functioning of the Na+ - K+ pump. e.g., anoxia --- impairing ~ --- loss of K+ from the cells. Na+ - K+ ion exchange pumps in the cell membrane.--- maintenance of high intracellular K+