Renal structure and function of the renal tubule Flashcards
What are the juxtamedullary nephrons key to?
The juxtamedullary nephrons are key to the maintenance of counter-current mechanism
What are the 2 types of nephrons?
-Cortical nephron
-Juxtamedullary nephron
What is the function of cortical nephrons?
Cortical nephrons (85% of all nephrons) mainly perform excretory and regulatory functions
What are the tubules responsible for and what does this maintain?
The tubules are responsible to convert the 180 litres of crude glomerular filtrate into high
quality “fit-for-purpose” urine, to maintain body’s salt-water-electrolyte balance
What is the equation for total urine?
Glomerular filtration 180L + Tubular reabsorption 178L secretion = Urine 2L
Which tubule does majority of reabsorption take place?
Majority of the reabsorption including 65% of water occurs at the proximal convoluted tubule
What type of cells are in the proximal convoluted tubule?
Tall cells with numerous
microvilli and mitochondria
What does malfunction of the proximal convoluted tubule cause?
Malfunction causes acidosis and
“fanconi syndrome”
What is the descending limb of loop of henle permeable to?
The descending limb of loop of Henle is permeable to water
What type of cells does the ascending limb of henle have and what does it transport out of the tubule?
The ascending limb has thicker cells with mitochondria, transports electrolytes out of the tubule
What mechanism is the loop of henle responsible for?
The loop is responsible for counter current mechanism
What diuretics work at the loop of henle?
“Loop diuretics” work here
What are the distal convoluted tubule responsible for?
Responsible for more
reabsorption of electrolytes and
water
What type of cells are present in the distal convoluted tubule?
Tall cells with numerous
mitochondria
What apparatus does the distal convoluted tubule include?
Includes the juxtaglomerular
apparatus
What diuretics work at the distal convoluted tubule?
The thiazide diuretics work here
What is the collecting duct responsible for?
Responsible for water
absorption
What are the 2 major types of cells in the collecting duct?
-Principal cells
-Intercalated cells
What is the structure and responsibility of principal cells?
tall, responsible for sodium absorption and
vasopressin action
What is the structure and responsibility of intercalated cells?
Intercalated cells – more microvilli, numerous
mitochondrion and responsible for
acid secretion
Where is majority of sodium absorbed and by what channel ?
Majority absorbed in proximal tubule by a Na-H exchanger
At what site is sodium absorbed in thick ascending loop of henley?
Na-2Cl-K
What channel is sodium absorbed in distal tubule?
Na-Cl cotransporter
What channel is sodium absorbed in distal convoluted tubule?
Epithelial Na channel
What is the total daily osmotic load to be excreted?
The total daily osmotic load to be excreted is 700 mOsm
What do vasopressin or antidiuretic hormones regulate from daily osmotic load?
The vasopressin or anti-diuretic hormone [ADH] regulates the volume of urine to excrete the daily osmotic load.
What happens when there is an increase in salt and water delivery at the distal tubule?
Tubulo-glomerular feedback
-Afferent artery vasoconstriction
-Decrease in filtration pressure
-Decrease in GFR
What is TGF with SGLT2i associated with and what has it shown improvement with?
TGF with SGLT2i is associated with slowing CKD
& improvement in HF hospitalisations and mortality
What is the countercurrent mechanism in the loop of henle responsible for?
Mechanism by which the osmotic gradient is generated in the medulla
What is the countercurrent mechanism generated by in the loop of henle?
Generated by differential movement of water in 2 limbs of loop of Henle
How is the counter current formed in the loop of henle?
The osmotically active molecules [Na,Cl,K] are pumped out from the ascending limb of loop of Henle generating hyperosmolar medulla which drives water out along osmotic gradient in descending limb
What is the countercurrent mechanism created by the vasa-recta?
Created by movement of water and electrolytes between the descending and ascending vasa-recta
What is the process by which the countercurrent mechanism is generated in vasa-recta?
water moves out and NaCl moves in the descending and vice versa in ascending
