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absorption and secretion in the kidneys (renal tubule (PCT (directly…
absorption and secretion in the kidneys
absorption
from tubular fluid (what will be urine) to tubular epithelial cells to peritubular space and finally to blood
function:
get back things that were filtered in glomerulus that the body needs (only formed elements and things bound to large proteins don't go into tubular fluid)
secretion
from blood to peritubular space, to tubular epithelial cells, and finally to tubular fluid
function:
organic anions/cations such as bile salts or antibiotics that are not filtered in renal corpuscle can be released via peritubular capillary
it also provides a way to regulate fluid, electrolyte, and pH balance
renal tubule
PCT
directly connected to Bowman's capsule
absorbs most of the glucose, amino acids, electrolytes, and H2O (has a lot of transporter proteins and microvilli)
67% of Na absorption happens here
glucose is absorbed using Na+/glucose
cotransport
(
secondary active
: Na+/K+ ATPase pays for it on the basal side)
sodium is absorbed in
early PCT
using a H+/Na+
antiporter
(
secondary active:
Na+/K+ ATPase pays for it on the basal side)
sodium is absorbed in
late PCT
using H+/Na+ antiporter
AND
chloride is absorbed using a Cl-/formate- antiporter
loop of Henle
(25% of NaCL absorb.)
descending limb:
only permeable to water, water moves back to blood (osmosis)
thin ascending limb:
only permeable to solute passively (
NOT WATER
)
thick ascending limb:
secondary active transport of Cl-, Na+, and K+ via Na+/K+/2Cl- cotransporter (
NOT PERMEABLE TO WATER
)
collecting system
NOT part of a nephron
receives tubular fluid from many nephrons
has receptors for
ADH (causes aquaporin2 channels open)
and aldosterone
DCT
opens to the collecting tubule
early DCT:
absorbs Na+ via Na+/Cl- cotransporter (
NOT PERMEABLE TO WATER
)
late DCT:
absorbs Na+
glucose + O2 = ATP
loop diuretics
stops action of the Na-K-2CL transporter in loop of Henle
blocks ~25% of Na+ reabsorption
ex: furosemide
juxtamedullary nephrons
allow for production of
concentrated urine