Physiology 502 Renal Nephron Segments

renal corpuscle

filtration occurs here

proximal tubule

70-80% of solutes and H2O are reabsorbed here

Secretion of H+ and of inorganic anions and cations occurs here

loop of henle

cortical loops are involved in the reabsorption of filtered Na+ and H2O (reabsorb about 25% of filtered load)

H2O

descending segment of the loop of henle reabsorbs ____

Na+

ascending segment of the loop of henle reabsorbs 25% of filtered load of ____

juxtamedullary loop

due to their longer length and the surrounding vasa recta capillaries, solute builds up in the medulla and creates a unique hypertonic ISF environment

proximal tubule

bulk reabsorber

distal tubule

small amount of reabsorption of solutes (mostly NaCl) without H2O

late distal tubule (connecting tubule)

transition segment - small amount of solutes and water reabsorbed

cortical collecting duct

aldosterone regulates Na+ reabsorption and K+ secretion here

medullary collecting duct

ADH regulates H2O reabsorption here

proximal tubule

65% of filtered load of Na+ reabsorbed here

proximal tubule

70-80% of filtered load of H2O reabsorbed here

distal tubule

5% of filtered load of Na+ reabsorbed here

cortical collecting duct

4-5% of filtered load of Na+ reabsorbed here (regulated by aldo)

(entire) collecting duct

5-10% of filtered load of H2O reabsorbed here (regulated by ADH)

aldosterone

steroid hormone released from the adrenal gland that In late distal tubule/cortical collecting duct cells: increases Na/K pumps on basolateral membrane, increases ENaCs and ROMK channels on apical membrane (which causes Na+ reabsorption and K+ secretion)

Angiotensin II

peptide generated in the plasma that stimulates Na+ reabsorption in the proximal tubule via NHE3 and the Na+/H+ exchanger

BNP

this chemical detects ventricular distention which increases its concentration and therefore causes increased GFR through afferent arteriole dilation and efferent constriction and also decreases plasma aldosterone levels at the adrenal glands (causes decreased reabsorption of Na+ and H2O)

ANP

detects atrial distention which increases its concentration and therefore causes increased GFR through afferent arteriole dilation and efferent constriction and also decreases RAAS to decrease Na+ and H2O reabsorption

K+

98% of total body ___ is intracellular

proximal tubule

55% of filtered load of K+ is reabsorbed here

loop of henle

30% of filtered load of K+ is reabsorbed here

collecting duct

K+ can be secreted in this segment

proximal tubule

80% of HCO3- reabsorbed here

can also metabolize glutamine here

ascending loop of henle

10% of HCO3- reabsorbed here

distal tubule

6% of HCO3- reabsorbed here (able to add new HCO3- to plasma or secrete HCO3- here)

cortical collecting duct

4% of HCO3- reabsorbed here (can also add HCO3- to plasma and in rare cases excrete HCO3- here)