Conservation of Water—Guggino
a. Daily Excretion: 700ml thru skin, lungs, etc; 900ml thru kidney (urine)
b. Daily Intake: 300ml from metabolism; => NEED 1300ml drinking!
c. Urine entering glomerulus is isotonic (300mOsm/L) w/ plasma
d. Ability of the loop of Henle to concentrate urine is directly related to the length of
the long loops (relative thickness of the medulla)
II. Countercurrent exchange
a. Vasa Recta—capillary system composed of long loops that extend down into the
medulla & ascend (the two vessels are closely adhered); freely permeable to H2O
b. As vasa recta descends, it loses H2O and absorbs salt; as it ascends, it gains H2O
and loses salt
c. H2O returns to vasa recta & salts remain in interstitum => body has way to supply
nutrients & O2 w/o upsetting gradient!
III. How does Loop of Henle transport salt & H2O?
* Nephron segments within henle’s loop have different functional characteristics
a. Different passive permeabilities—TDL is permeable to H2O not salt, etc
b. Active transport—thick ascending limb (TALH) is only segment to actively
transport NaCl (via cotransport) => provides