Lecture 38

Question 1

Function of glmoerular filtration is where…

Answer 1

Selected components of the plasma are allowed to enter the bowman caopsule to the nephron (first step in urine formation)

Question 2

Which portion of the nephron contributes most to the reclaiming of useful substances

Answer 2

Proximal convoluted tubule

Question 3

Tubular reabsorbtion

Answer 3

Water and other useful substances are reclaimed by the kidneys tubules

Question 4

Specialisations of the PCT

Answer 4

Microvilli - ↑ surface area

Fenestrated capillaries around PCT to aid exchange of substance

Question 5

Reabsorbed molecules and how

Answer 5

Water - conc gradients
Urea - passive diffusion
Glucose- Glut2 transporters- facilitated diffusion trans cellular
Glucose also has SGLT-1+2 receptors (Sodium conc gradient)- active transport
Potassium sodium- primary active transport

Question 6

SGLT1 and 2 relationship to GLUT1 and 2

Answer 6

SGLT1+2 move glucose across from filtrate into tubular cell

Glut1+2 move glucose from cell to blood

Question 7

What limits the transport of glucose?

SGLT1 GLUT1

Answer 7

Too much glucose to reabsorbed through transporters = glucosuria eg diabetes

Disfunction of the SGLT1/2 receptors, due to drug inhibition

ONLY IN PCT

Question 8

AMINO ACID REABSORPTION

Answer 8

PCT
Carried out by SLC (solute carrier proteins)

Aminoaciduria caused by

• high plasma AA (metabolic disease)
• disfunction of receptors (hartnup disease)

Question 9

Reabsorption of sodium

Answer 9

Active transport transcellular
Secondary active transport (with glucose, AA or H+)
PCT initially
Further reabsorption in ascending loop via co transporters
DCT via co transporters

Question 10

Benefit of sodium wasting and how

Answer 10

In times of hypertension or HF, this can ↓ BP by ↓ water levels in the blood
Sodium excretion = water loss via urine

Diuretics
- spironolactone =
prevents the effects of aldosterone ↓ sodium pump ↓ reabsorbtion

• loop diuretics
  = inhibit co transporters in the ascending loop
• thiazides
  = inhibit co transporter in the DCT

Question 11

Spironolactone use

Answer 11

Prevents sodium reabsorbtion by ↓ the effects of aldosterone on Na+/K+ pump expression which helps reabsorb sodium

Question 12

Loop diuretics use

Answer 12

Inhibits the Na/Cl/K transporter in ascending loop

Question 13

Thiazide Duirrtics use

Answer 13

Inhibits Na+/Cl- transporter in DCT

Question 14

Water reabsorption

Answer 14

Movement across and through membranes as a result of the gradient produced by sodium

Question 15

What facilitates water reabsorption

Answer 15

Aquapourins

Question 16

H2O reabsorption in loop of henle

Answer 16

Counter multiplier

Sodium pumped out of ascending limb into the vasa recta
Blood very concentrated
Makes its way to the water permeable descending limb
Water drawn out into the vasa recta by conc gradients

Leads to v concentrated filtrate, keeping the process going

Question 17

Production of urea

Answer 17

Protein metabolism

Question 18

Reabsorption of urea

Answer 18

1. Through bowman capsule
2. Reabsorbed in the PCT (50%)
3. Facilitated diffusion in ascending limb urea INTO THE FILTRATE
4. Further reabsorption in the collecting ducts
5. 20% excreted

Question 19

Uraemia is a sign of…

Answer 19

Renal failure as it is the only pathway for urea out of the body
Most likely have other conditions too.

Question 20

Why is reabsorption of urea so important in collecting ducts?

Answer 20

Adds to the hyper-osmolarity which allows for the osmotic uptake of water.

Question 21

Secretion in the kidneys

Answer 21

Movement from the blood plasma into the filtrate

Useful in excretion of toxins like… creatinine, uremic toxins, drug clearance, antibiotics NSAID and statins.