Tubular Structure & Function

Question 1

What are the two types of Nephrons? How are they different

Answer 1

Superficial cortical: 85%, short loops of Henle

Juxtaglomerular: 15%, long loops of Henle

Question 2

What are the two main modes of transport for material to move from the Lumen into the Interstitial fluid?

Answer 2

• Paracellular route (between tight junctions)

- Transcellular route

Question 3

What is the tubular maximum rate for glucose?

Answer 3

300 mg / min

Question 4

Where does the drug Furosemide work on in the kidney?

Answer 4

Ascending limb of loop of Henle

Question 5

Where do Thiazide diuretics work on in the kidney?

Answer 5

Distal convoluted tubule

Question 6

Where does the drug Amiloride work on in the kidney?

Answer 6

Collecting duct

Question 7

Which segment of the nephron reabsorbs most of the glomerular filtrate? What proportion?

Answer 7

Proximal Convoluted Tubule, 66%

Question 8

Which SGLT transporters are located in the early proximal tubule and the late proximal tubules?

Answer 8

Early PCT: SGLT2

Late PCT: SGLT1

Question 9

SGLT2 shuttles how many ions with glucose into the tubule lumen?

Answer 9

1Na+ with Glucose

Question 10

SGLT1 shuttles how many ions with glucose into the tubule lumen?

Answer 10

2Na+ with Glucose

Question 11

In the early proximal tubule, state the three transporters involved in Glucose transport

Answer 11

SGLT2
GLUT2
3Na+/2K+ transporter

Question 12

In the late proximal tubule, state the three transporters involved in Glucose transport

Answer 12

SGLT1
GLUT1
3Na+/2K+ transporter

Question 13

Why are polyuria, glucosuria and polydypsia symptoms of Diabetes mellitus?

Answer 13

In DM patients, the plasma glucose exceeds Tm, which leads to glucosuria. Because glucose is osmotically active, water is also moved with it, leading to polyuria. This loss in water leads to polydypsia

Question 14

How are single amino acids handled by the PCT?

Answer 14

99% is reabsorbed by the PCT, the remaining 1% in the late PCT. Multiple amino acid transporters are involved

Question 15

How are small peptides handled by the PCT?

Answer 15

99% are reabsorbed by the PCT via brush border enzymes which hydrolyse >4 amino acid peptides into single AAs. Short peptides (2-4 AAs) are reabsorbed by an oligopeptide co-transporter and then metabolised by peptidases

Question 16

How are large proteins such as albumin / peptides handled by the PCT?

Answer 16

• Taken up by the PCT via clathrin-coated mediated endocytosis
• When inside, will combine with endosome and then lyosome to be degraded into free AAs

Question 17

Describe the permeability of ions / urea / water in the Descending limb Loop of Henle

Answer 17

• Low permeability to ions / urea

- High permeability to water

Question 18

Describe the permeability of ions / urea / water in the Ascending limb Loop of Henle

Answer 18

• Impermeable to water

- Permeable to ions (active transport)

Question 19

What is the DCT mainly responsible for?

Answer 19

Regulation of potassium, sodium, calcium, and pH

Question 20

State four influences which help retain Na+ in the plasma

Answer 20

1. RAAS
2. Renal nerve stimulation
3. Noradrenaline
4. Vasopressin

Question 21

State four influences which help lose Na+ in the plasma

Answer 21

1. Atrial natriuretic peptide
2. Prostaglandins
3. Bradykinin
4. Dopamine

Question 22

A human produces how much urine per day?

Answer 22

1.5 ltr a day

Question 23

What is a normal GFR (Glomerular filtration rate)?

Answer 23

120 ml/min

180l/day

Question 24

In the counter-current multiplier, once H2O moves out of the descending limb - what happens to it to help maintain a gradient?

Answer 24

It is removed by the vasa recta and H2O is returned to circulation

Question 25

Vasopressin binds to what receptors on the basal membrane to help insert aquaporins on the apical membrane?

Answer 25

V2 receptors