Proximal tubule, loop of henle,dct Flashcards
Proximal tubule
Na+IN,
H+ OUT
by Na+/H+ Exchanger (NHE3)
Proximal tubule
H+ + HCO3- = H2CO3 (carbonic acid) → H2O (water) + CO2 (carbon dioxide)
by ___________________ (CA)
carbonic anhydrase
Proximal tubule
CO2 (carbon dioxide) IN by diffusion → H2CO3
Proximal Tubule
3. CO2 IN by diffusion → H2CO3
4. H2CO3 → H+ + HCO3- by Carbonic Anhydrase (CA)
5. Na +, HCO3- IN to Interstitial space
by Na +-HCO3- symporter
(= cotransporter)
Proximal tubule
Glucose and Na+ reabsorption
by _____________________(SGLT2)
Sodium-glucose cotransporter type 2
Proximal tubule
Sodium-glucose cotransporter type 2 expressed on the _________ membrane of the proximal tubule
apical
In PCT
________ of glucose reabsorption, and 5% of Na+
reabsorption
Electrochemical gradient of Na+ provides the free energy to
reabsorb glucose
90%
Glomerulus, PCT,and thin descending limb of loop of Henle has high water permeability
Proximal Tubule
Reabsorption
Water
Highly permeable membrane
→RAPID osmotic movement of
water → equal osmolality
→Reabsorbs Na+ and water in
equal proportions
Proximal Tubule
Glucose, amino acids, lactate,
water-soluble vitamins → ~ 100%
Electrolytes Na+, Cl−,K+, Ca2+, Mg2+ → ~ 65%
HCO3- → ~ 85%
Proximal Tubule
Secretion: H+, drugs, creatinine
Loop of Henle (=Nephron loop)
1.Thin descending limb
2. Thick ascending limb
3. ________________ (TAL) – Diluting segment
* Controlling the concentration of the urine
Thick ascending limb
Renal medulla has a higher renal osmolarity
The Countercurrent Multiplier of the Nephron Loop
Nephron loop multiplies the osmolarity deep in the medulla → “____________”
Fluid in the nephron loop flow in opposite directions in two adjacent tubules (downward in the descending limb and upward in the ascending limb) → “________________”
Multiplier
Countercurrent
Water is drawn from blood by the osmotic gradient during passage down through the medulla. Water then reenters during ascent
Reabsorption of water, driven by the osmotic gradient btwn _________ and interstitium
vasa recta
Countercurrent exchange in the vasa recta
The rate of reabsorption from medullary interstitium into the vasa recta is slower compared to the tubular reabsorption → Maintain medullary ___________ gradient.
osmotic gradent
Vasa recta walls are permeable, allowing solutes to enter and leave passively
In which section of the Loop of
Henle does the reabsorption of
solutes occur primarily?
A. Thin descending limb
B. Thin ascending limb
C. Thick ascending limb (TAL)
The Loop of Henle – Thick Ascending Limb
Low permeability to_______________
water
The Loop of Henle – Thick Ascending Limb
Na+, Cl-, K+, Ca2+, Mg2+ IN
Loop of Henle-Thick Ascending Limb
Na+/K+/2Cl− cotransporter(__________) is the primary transporter in the luminal(apical) membrane.
(NKCC2)
The loop of Henle-Thick Ascending Limb
The positive electrical potential by K+ back diffusion → Ca2+ , Mg2+ via the _____________pathway.
paracellular
Thin Descending limb
High permeability to water H2O IN
Thick Ascending Limb
Low permeability to water
Na+ (25%), Cl-, K+ IN
Ca2+, Mg2 IN
Early distal tubule
Reabsorption: Na+, Cl-, Ca++, Mg++
Tubuloglomerular Feedback in the Juxtaglomerular Apparatus
Mechanism
The glomerulus receives feedback
on the status of the downstream
tubular fluid and adjusts filtration to
regulate its composition, and
compensate for fluctuations in BP
Macula densa cells
At the beginning of the ____
Close to granular cells
Sensing Cl- from Na+/K+/2Cl− cotransporter
Granular cells
-Release ___________.
DCT
renin
Reabsorption: NaCl by Na+/Cl- symporter (_____) in DCT
NCC
