Renal structure and function of the renal tubule

Question 1

What are the juxtamedullary nephrons key to?

Answer 1

The juxtamedullary nephrons are key to the maintenance of counter-current mechanism

Question 2

What are the 2 types of nephrons?

Answer 2

-Cortical nephron
-Juxtamedullary nephron

Question 3

What is the function of cortical nephrons?

Answer 3

Cortical nephrons (85% of all nephrons) mainly perform excretory and regulatory functions

Question 4

What are the tubules responsible for and what does this maintain?

Answer 4

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

Question 5

What is the equation for total urine?

Answer 5

Glomerular filtration 180L + Tubular reabsorption 178L secretion = Urine 2L

Question 6

Which tubule does majority of reabsorption take place?

Answer 6

Majority of the reabsorption including 65% of water occurs at the proximal convoluted tubule

Question 7

What type of cells are in the proximal convoluted tubule?

Answer 7

Tall cells with numerous
microvilli and mitochondria

Question 8

What does malfunction of the proximal convoluted tubule cause?

Answer 8

Malfunction causes acidosis and
“fanconi syndrome”

Question 9

What is the descending limb of loop of henle permeable to?

Answer 9

The descending limb of loop of Henle is permeable to water

Question 10

What type of cells does the ascending limb of henle have and what does it transport out of the tubule?

Answer 10

The ascending limb has thicker cells with mitochondria, transports electrolytes out of the tubule

Question 11

What mechanism is the loop of henle responsible for?

Answer 11

The loop is responsible for counter current mechanism

Question 12

What diuretics work at the loop of henle?

Answer 12

“Loop diuretics” work here

Question 13

What are the distal convoluted tubule responsible for?

Answer 13

Responsible for more
reabsorption of electrolytes and
water

Question 14

What type of cells are present in the distal convoluted tubule?

Answer 14

Tall cells with numerous
mitochondria

Question 15

What apparatus does the distal convoluted tubule include?

Answer 15

Includes the juxtaglomerular
apparatus

Question 16

What diuretics work at the distal convoluted tubule?

Answer 16

The thiazide diuretics work here

Question 17

What is the collecting duct responsible for?

Answer 17

Responsible for water
absorption

Question 18

What are the 2 major types of cells in the collecting duct?

Answer 18

-Principal cells
-Intercalated cells

Question 19

What is the structure and responsibility of principal cells?

Answer 19

tall, responsible for sodium absorption and
vasopressin action

Question 20

What is the structure and responsibility of intercalated cells?

Answer 20

Intercalated cells – more microvilli, numerous
mitochondrion and responsible for
acid secretion

Question 21

Where is majority of sodium absorbed and by what channel ?

Answer 21

Majority absorbed in proximal tubule by a Na-H exchanger

Question 22

At what site is sodium absorbed in thick ascending loop of henley?

Answer 22

Na-2Cl-K

Question 23

What channel is sodium absorbed in distal tubule?

Answer 23

Na-Cl cotransporter

Question 24

What channel is sodium absorbed in distal convoluted tubule?

Answer 24

Epithelial Na channel

Question 25

What is the total daily osmotic load to be excreted?

Answer 25

The total daily osmotic load to be excreted is 700 mOsm

Question 26

What do vasopressin or antidiuretic hormones regulate from daily osmotic load?

Answer 26

The vasopressin or anti-diuretic hormone [ADH] regulates the volume of urine to excrete the daily osmotic load.

Question 27

What happens when there is an increase in salt and water delivery at the distal tubule?

Answer 27

Tubulo-glomerular feedback -Afferent artery vasoconstriction -Decrease in filtration pressure -Decrease in GFR

Question 28

What is TGF with SGLT2i associated with and what has it shown improvement with?

Answer 28

TGF with SGLT2i is associated with slowing CKD & improvement in HF hospitalisations and mortality

Question 29

What is the countercurrent mechanism in the loop of henle responsible for?

Answer 29

Mechanism by which the osmotic gradient is generated in the medulla

Question 30

What is the countercurrent mechanism generated by in the loop of henle?

Answer 30

Generated by differential movement of water in 2 limbs of loop of Henle

Question 31

How is the counter current formed in the loop of henle?

Answer 31

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

Question 32

What is the countercurrent mechanism created by the vasa-recta?

Answer 32

Created by movement of water and electrolytes between the descending and ascending vasa-recta

Question 33

What is the process by which the countercurrent mechanism is generated in vasa-recta?

Answer 33

water moves out and NaCl moves in the descending and vice versa in ascending