16.6 role of the nephron in osmoregulation

Question 1

describe ultrafiltration and the production of glomerular filtrate

Answer 1

• afferent arteriole has diameter greater than efferent arteriole
• build up of hydrostatic pressure
• water, glucose, mineral ions are squeezed out
• proteins too large to leave
• endothelium of glomerular filtrate
• podocytes in the inner layer of the renal capsule

Question 2

adaptations of the proximal convoluted tubule

Answer 2

• microvilli to provide large surface area
• infolding’s to provide large surface area
• high density of mitochondria to provide ATP for active transport

Question 3

explain reabsorption of water by the proximal convoluted tubule

Answer 3

• Na⁺ are actively transported out of PCT
• Na+ concentration decreases
• Na+ diffuse down gradient from lumen of PCT into epithelial cells by facilitated diffusion
• co-transport of other molecules too
• molecules diffuse into the blood

Question 4

explain how a gradient of Na+ in the medulla of the loop of Henle is maintained

Answer 4

• ascending limb of the Loop of Henle is permeable to water
• Na+ actively transported out of ascending limb
• lowers the concentration as tubular fluid rises up ascending limb
• Na+ diffuse into descending limb
• raising concentration of tubular fluid as it passes down the descending limb

Question 5

explain the role of the distal convoluted tubule and the collecting duct in the reabsorption of water

Answer 5

• reabsorbed of material by active transport

- make final adjustment to the H₂O

Question 6

adaptations of the distal convoluted tubule to make final adjustments

Answer 6

• microvilli for a large surface area
• many mitochondria for ATP to actively transport material
• changes permeability