Kidney Structure

Question 1

Nephron

Answer 1

Functional unit of the kidney, wall are 1 cell thick

Question 2

How many nephrons are there per kidney?

Answer 2

I million

Question 3

Glomerulus

Answer 3

Capillary bed inside Bowman’s Capsule

Question 4

Vasa Recta

Answer 4

Capillary network surrounding each nephron, important for reabsorption and secretion

Question 5

Diluting

Answer 5

Above 300mOsm

Question 6

Dehydrating

Answer 6

Below 300mOsm

Question 7

Osmolarity of blood

Answer 7

300mOsm

Question 8

What determines how concentrated urine can be?

Answer 8

Loop of Henle length and size of osmotic gradient

Question 9

PCT

Answer 9

Proximal Convoluted Tubule, 2/3s of initial filtrate reabsorbed

Question 10

Descending Loop of Henle

Answer 10

Water reabsorption continues, osmolarity of pre-urine at bottom is 1200

Question 11

Ascending Loop of Henle

Answer 11

Salt reabsorption occurs here, not permeable to water

Question 12

Diluting Segment

Answer 12

Thick part of the ascending loop of henle, osmolarity at the end of the DS is 100mOsm

Question 13

Distal Convoluted Tubule and Cortical Collecting Duct

Answer 13

Action depends on hormones and acid-base balance, aldosterone stimulates Na+ reabsorption and K+ secretion, H+ can be secreted into pre-urine, permeable to H2O only when ADH is high

Question 14

ADH

Answer 14

Causes insertion of H2O channels through membrane, aquaporines, allows pre-urine to equilibrate with hi extracellular osmolarity of medulla

Question 15

Medullary Collecting Ducts

Answer 15

H2O reabsorption, permeable to H2O only when ADH is high, very permeable to urea

Question 16

Urea

Answer 16

A toxic nitrogenous waste product of protein metabolism, becomes concentrated approx 65x in the nephron, diffuses down its concentration gradient into the extracellular fluid and is passively transported

Question 17

Low ADH

Answer 17

Urine is approx 100mOsm

Question 18

High ADH

Answer 18

Urine is approx 1200mOsm

Question 19

Ethanol (ETDH)

Answer 19

Dehydrates by inhibiting ADH so there is no insertion of aquaporines

Question 20

3 Steps of Urine Formation

Answer 20

Filtration, reabsorption, and secretion

Question 21

Filtration

Answer 21

Driven by blood pressure in glomerulus, non-selective, 15-25% of water and solutes passing through glomerulus are filtered

Question 22

Reabsorption

Answer 22

99% of filtered H2O and salts are reabsorbed before kidney produces final urine, approx 100% of important cmpds like glucose, vitamins, and AAs are reabsorbed