16.6 role of nephron in osmoregulation

Question 1

describe the movement of blood starting from the renal artery to the renal vein.

Answer 1

renal artery -> Bowman’s capsule -> afferent arteriole -> glomerulus -> efferent arteriole -> renal vein

Question 2

what is in the glomerular filtrate?

Answer 2

H2O, glucose, mineral ions only

Question 3

why are blood cells and proteins not in the glomerular filtrate?

Answer 3

too large & don’t pass into renal capsule

Question 4

what are podocytes?

Answer 4

have spaces and allow filtrate to pass beneath & through gaps

Question 5

what are the 3 adaptations in the proximal convoluted tubules for reabsorption?

Answer 5

• microvilli - large SA
• infolding at basal membrane for large SA & to transfer reabsorbed substances to blood capilliaries
• high density of mitochondria - provide ATP for active transport

Question 6

describe the process of reabsorption. (3)

Answer 6

1) Na+ ions transported out by active transport of the cells lining PCT & into blood capilliaries -> Na+ ion concentration decreases

2) Na+ ions diffuse down conc. gradient in lumen of proximal convoluted tubule into epithelial cells (through facilitated diffusion with specific carrier proteins)
-> co-transport of amino acids/glucoze/Cl- ions

3) the transported molecules diffuse into the blood

Question 7

describe how the Na+ gradient is maintained by the loop of Henle. (6)

Answer 7

1- Na+ & Cl- actively transported out of ascending limb
-> leads to low water potential in medulla between interstitial region
- thick walls (of ascending limb) not permeable to H2O

2- walls of descending limb are permeable to H2O -> filtrate out by osmosis to interstitial space

3- H2O enter blood capilliaries by osmosis

4- filtrate loses H2O as it moves down descending limb & reaches lowest water potential

5- creates water potential gradient at interstitial space: highest at cortex & lower water potential further into medulla

6- varying permeability at collecting duct
- H2O passes out by osmosis into blood vessels
- lower water potential in filtrate & interstitial space at the same time; countercurrent multiplier makes H2O keeps moving out

Question 8

what adaptation does the distal convoluted tubule have that allow materials to be reabsorbed by active transport?

Answer 8

microvilli & many mitochondria

Question 9

how is the countercurrent flow an advantage of the loop of Henle?

Answer 9

steep water potential gradient maintained & water only moves out of the distal convoluted tubule