Ianowski - theme 5

Question 1

Order of nephron bits:

Answer 1

Glomerulus, proximal tubule, loop of Henle, distal tubule, collecting duct.

Question 2

Glomerulus:

Answer 2

Ultrafiltration. Small plasma molecules and water move from blood to nephron, driven by blood pressure. No cells enter the ultrafiltrate - low protein concentration. Podocytes control passage.

Question 3

Renal corpuscle: components

Answer 3

Glomerulus and glomerular/Bowman’s capsule

Question 4

Glomerular capsule:

Answer 4

Two layers. Outside layer keeps the capsule apart from everything else; inside layer does the actual filtering. Contains basement membrane between endothelial cells and podocytes.

Question 5

Basement membrane:

Answer 5

Involved in filtration. It’s negatively charged so plasma proteins don’t get through. Lets through water, ions, waste, and glucose.

Question 6

Rate of glomerular filtration:

Answer 6

115 mL/min, 7.5 L/hr

Question 7

Proximal convoluted tubule: job

Answer 7

Reabsorption - 65% filtered water, 67% filtered sodium, some glucose and AAs
Secretion - protons for acid/base regulation, some organic molecules

Question 8

Proximal convoluted tubule: how do job

Answer 8

Active transport - carrier mediated glucose and AA transport. Na/K pump produces sodium gradient, which can bring glucose as a +1.

Question 9

Tm:

Answer 9

Tubular maximum. Transporters are saturated; filtered glucose appears in urine.

Question 10

Absorption of protein in proximal tubule:

Answer 10

99% of protein is taken up again from the nephron. 1% may be excreted.

Question 11

Receptor-mediated endocytosis of proteins in proximal tubule:

Answer 11

Proteins are marked for destruction by lysosomes, then AAs can be pushed into interstitial space

Question 12

Loop of Henle: function

Answer 12

Establishes osmotic gradient in medulla. This allows water absorption (another 20%) from the collecting duct.

Question 13

How much water is left in the urine after passing through proximal tubule and the loop of Henle?

Answer 13

15%. 85% has been taken up.

Question 14

How does the loop of Henle establish osmotic gradient?

Answer 14

Descending limb is permeable to water and impermeable to NaCl. Filtrate becomes concentrated.
Ascending limb is impermeable to water. Actively transports Na out (Cl follows passively). Medulla fluid becomes concentrated, allowing the process in the descending limb to occur.

Question 15

What kind of feedback loop is used in the loop of Henle?

Answer 15

Positive feedback. The more Na is pumped out in the ascending limb, the more water can be reabsorbed in the descending limb. The more water reabsorbed in the descending limb, the more stuff for the ascending limb to pump out. ***

Question 16

Urea in the medulla:

Answer 16

Accumulates in the loop of Henle and gets peed out. ***

Question 17

Vasa recta:

Answer 17

Blood vessels! Takes up excess water and solutes with countercurrent exchange.
This is glomerular blood, not reg blood, so it has a high protein concentration and sucks up water cuz proteins are thirsty.

Question 18

Why does the vasa recta loop up instead of exchanging blood at the bottom?

Answer 18

Blood at the bottom has a high ion concentration, which you don’t want to lose. Follow the gradient back up to low concentration before feeding into vein.

Question 19

Distal convoluted tubule: what it do

Answer 19

May dilute filtrate. Regulates Na/K in the blood by aldosterone-controlled Na transport and ADH-controlled water permeability.

Question 20

Distal convoluted tubule: the parts

Answer 20

Collecting duct and interlobular vein

Question 21

Collecting duct:

Answer 21

Concentrates urine using the medulla’s gradient. In high water concentration, ADH blocks water exchange so it can be peed out. In low water concentration, the gradient pulls water out of the urine.

Question 22

I gotta ask again - what’s another name for vasopressin?

Answer 22

ADH, antidiuretic hormone. I KEEP FORGETTING AND I’M SORRY.