SM_192a: Functions of the Renal Tubule II Flashcards
Cortical nephrons have _____ loops of Henle, while medullary nephrons have _____ loops of Henle
Cortical nephrons have short loops of Henle, while medullary nephrons have longth loops of Henle
______ is near the thick ascending limb of the loop of Henle the past the vascular pole
Macula densa is near the thick ascending limb of the loop of Henle the past the vascular pole
Describe the difference in histology between the outer stripe of the outer medulla, inner stripe of the outer medulla, and inner medulla
Histology
- Outer stripe of outer medulla: homogeneous in cellular composition
- Inner stripe of outer medulla: see thin walled segments
- Inner medulla: only see collecting ducts with cellular heterogeneity and thin segments
Thick ascending limb of loop of Henle is thicker due to presence of more ______
Thick ascending limb of loop of Henle is thicker due to presence of more mitochondria
Juxtaglomerular appratus includes _____, _____, and _____
Juxtalgomerular apparatus includes macula densa, extraglomerular mesangial cells, and granular cells in wall of afferent arteriole
In apical membrane of thick ascending limb of the loop of Henle, ______ is the main transporter to get Na+ into the cell
In apical membrane of thick ascending limb of the loop of Henle, Na+/K+/Cl- symporter is the main transporter to get Na+ into the cell
(blocked by furosemide)
Describe Na+ reabsorption in the thick ascending limb of the loop of Henle
Na+ reabsorption in the thick ascending limb of the loop of Henle
- Enters cell from lumen by crossing apical membrane through Na+/K+/2Cl- symporter
- Pumped out into interstitium by Na+/K+ ATPase
In thick ascending limb of loop of Henle, ____ leaks back out into lumen from cells and is recycled
In thick ascending limb of loop of Henle, K+ leaks back out into lumen from cells and is recycled
Thick ascending limb of loop of Henle has no _____ channels so _____ permeability is low
Thick ascending limb of loop of Henle has no H2O channels so H2O permeability is low
(asymmetry between descending and ascending loop of Henle is important for countercurrent multiplier)
In the thick ascending limb of loop of Henle, ______ can cross into the interstitium do to unpaired negative charge on the interstitial side and K+ on the lumen side
In the thick ascending limb of loop of Henle, divalent cations (Ca2+, Mg2+) can cross into the interstitium do to unpaired negative charge on the interstitial side and K+ on the lumen side
(paracellin-1)
Ca2+ sensing receptor _____ sodium reabsorption
Ca2+ sensing receptor dampens sodium reabsorption
(balances calcium reabsorption - if impaired, unrestricted Ca2+ reabsorption so familial hypercalcemia w/ hypocalcuria)
The purpose of the countercurrent multiplier is to _______
The purpose of the countercurrent multiplier is to create a gradient of osmolality from cortex to medulla which creates a driving force for water to be absorbed in the collecting duct
(hyperosmotic interstitium in inner medulla)
(important for water absorption and concentration of urine)
Water permeability is high in the _______ and _______ of the nephron
Water permeability is high in the proximal tubule and descending limb of loop of Henle of the nephron
(in presence of ADH, collecting duct converted to high water permeability)
Describe the countercurrent multiplier
Countercurrent multiplier
- Active transport of NaCl from ascending limb to interstitial space
- Water moves from descending limb into interstitial space due to osmotic gradient
- Occurs iteratively until steady state is reached
- Hyperosmotic interstitium is produced in inner medulla
- Can extract water from the collecting duct
_____ and _____ are main contributers of osmolality in countercurrent multiplication
NaCl and urea are main contributers of osmolality in countercurrent multiplication
Role of the peritubular capillaries (vasa recta) in countercurrent multiplication is to ______
Role of the peritubular capillaries (vasa recta) in countercurrent multiplication is to passively uptake solute and release water
(in sick cell, blood cells clog up vasa recta in inner medulla -> microinfarctions -> attenuates number of long loops of Henle that can concentrate urine)
Distal convoluted tubule has a _____ wall and many _____
Distal convoluted tubule has a thick wall and many mitochondria
Describe reabsorption in the distal convoluted tubule
Reabsorption in the distal convoluted tubule
- Amount of reabsorption lower than preceding portions (lower fraction of reabsorbed NaCl)
- NaCl transporter to transport Na+ into cell and Na+/K+ ATPase to transport Na+ into interstitium
- Ca2+ exits cells through the Ca2+/3Na+ antiporter (if stop sodium reabsorption, potentiate calcium entry)
- Water cannot cross apical membrane
(if high calcium, more prone to form kidney stones)
_____ target the Na+/Cl- symporter in the apical membrane of the distal convoluted tubule
Thiazides target the Na+/Cl- symporter in the apical membrane of the distal convoluted tubule
Describe the functions of the cortical and medullary collecting duct
- Cortical collecting duct: reabsorbs Na+, secretes and reabsorbs acid/bicarbonate, reabsorbs water in presence of ADH
- Medullary collecting duct: reabsorbs Na+, secretes and reabsorbs acid/bicarbonate, reabsorbs water in presence of ADH, reabsorbs urea
_____ collecting duct reabsorbs urea
Medullary collecting duct reabsorbs urea
_____ is formed by collecting ducts of adjacent nephrons
Early collecting duct is formed by collecting ducts of adjacent nephrons
Cortical collecting duct is comprised of _____ cells and _____ cells
Cortical collecting duct is comprised of principal cells and intercalated cells
- Principal cells: Na+ reabsorption (contains Na+/K+ ATPase pumps in basolateral membrane)
- Intercalated cells: H+, bicarbonate secretion, and reabsorption
Collecting duct has _____ epithelia
Collecting duct has tight epithelia (high resistance)
(can withstand steep gradients of charge and pH)
Principal cells allow reabsorption of ____ and secretion of ____
Principal cells allow reabsorption of Na+ and secretion of K+
(impermeable to water)
_____ blocks Na+ in the cortical collecting duct
Amiloride blocks Na+ in the cortical collecting duct
Aldosterone binds to the _____ receptor which upregulates the _____ and _____, promoting _____ from the principal cells of the cortical collecting duct
Aldosterone binds to the intracellular mineralocorticoid receptor which upregulates the Na+ channel in the apical membrane and Na+/K+ ATPase in the basolateral membrane, promoting Na+ reabsorption from the principal cells of the cortical collecting duct
____ mediates aldosterone action in the principal cells of the cortical collecting duct by promoting placement of more ____ channels in the membrane
SGK1 mediates aldosterone action in the principal cells of the cortical collecting duct by promoting placement of more Na+ channels in the apical membrane
(phosphorylates NED4-2 -> prevents ubiquitin-mediated degradation of Na+ channels -> more Na+ channels in apical membrane)
_____ receptors increase water permeability in the principal cells of the cortical collecting duct
Vasopressin receptors increase water permeability in the principal cells of the cortical collecting duct
(promote reabsorption of water)
Intercalated cells of the cortical collecting duct regulate _____
Intercalated cells of the cortical collecting duct regulate acid-base
_____ intercalated cells of the cortical collecting duct secrete acid
Type A intercalated cells of the cortical collecting duct secrete acid
- Vaculoar pump is used forn transepithelial proton secretion
- Carbonic anhydrase eventually generates bicarb
______ intercalated cells of the cortical collecting dudct secrete base
Type B intercalated cells of the cortical collecting duct secrete base
Describe the important transporters in the inner medullary collecting duct
Inner medullary collecting duct
- ANP receptor on basolateral membrane causes natriuresis (inhibition of Na+ reabsorption) by inhibiting cGMP
- Urea transporters allow urea to enter collecting duct cells and then leave to be concentrated in the interstitium
- Vasopressin receptors allow reabsorption of water
