Nephron segment | Major functions |
Glomerulus | Forms an ultrafiltrate of plasma |
Proximal tubule | Reabsorbs isosmotically 60 to 65 percent of the filtered NaCl and H2O Reabsorbs 90 percent of the filtered HCO3- Major site of ammonia production in the nephron Reabsorbs almost all of filtered glucose and amino acids Reabsorbs K+, phosphate, calcium, magnesium, urea, and uric acid Secretes organic anions (such as urate) and cations (such as creatine); this pathway is also used for excretion of protein-bound drugs and toxins |
Loop of Henle | Reabsorbs 25 to 35 percent of filtered NaCl Countercurrent multiplier as NaCl reabsorbed in excess of water Major site of active regulation of magnesium excretion |
Distal tubule | Reabsorbs about 5 percent of filtered NaCl but almost no water Major site, with connecting segment, of active regulation of calcium excretion |
Connecting segment and cortical collecting tubule | Principal cells reabsorb Na+ and Cl- and secrete K+ under the influence of aldosterone Intercalated cells secrete H+, reabsorb K+, and, in metabolic alkalosis, secrete HCO3- Reabsorb water in the presence of antidiuretic hormone |
Medullary collecting tubule | Site of final modification of the urine Reabsorb NaCl, the concentration of which can be reduced to less than 1 meq/L Reabsorb water and urea relative to the amount of antidiuretic hormone present, allowing a concentrated or dilute urine to be excreted Secrete H+ and NH3; urine pH can be reduced to as low as 4.5 to 5.0 Can contribute to potassium balance by reabsorption or secretion of K+ |
آیا می خواهید مدیلیب را به صفحه اصلی خود اضافه کنید؟