(13) - Urine Concentration and Dilution

Question 1

(Key Points)

1. Generation of a medullary concentration gradient is essential for doing what?
2. The reabsorption of sodium in the thick ascending limbs of the loop of Henle where the tubules are impermeable to water is of primary importance in generating what?

Answer 1

1. altering urine concentration
2. concentrated or dilute urine

Question 2

(Key Points)

1. separation of solute and water, continuous flow of fluid through the loop of Henle, and the relationship between the ascending and descending limbs of the loop of Henle allow for generation of what?
2. Movement of fluid in opposite directions in Henle’s loops “mutliplies” changes in tubule osmolaltiy, thus doing what?

Answer 2

1. the medullary concentration gradient
2. increasing the concentration gradient

Question 3

(Key Points)

1. ADH influences urine concentration by inducing insertion of what in to what? thus allowing what?

Answer 3

1. insertion of aquaporin-2 into portions of the distal nephron; equilibration between the tubular lumens and concentration gradient

Question 4

purpose of vascular structures is to supply nutrients and to get waste products extracted - but vasa recta has to do it without taking fluid out - vasa recta designed not to pick up salt and take it back into the body

Answer 4

Question 5

(Constituents and MEchanisms)

(medullary solutes)

1. salt
2. urea

(how do the solutes get there?)

3-4. what two ways?

Answer 5

3. countercurrent multiplication (loops of Henle, deposits salt in medullary gradient)
4. urea recycling (inner medullary collecting ducts)

Question 6

(Medullary Osmotic Gradient)

(Three major components)

1. Active reabsorption of Na from the ascending limb of the LH in to what?
2. Recycling of urea between what and what?
3. Vasa recta structure with close appostion between what and what? high or low flow rates?

Answer 6

1. the medullary intersitium
2. MCD and deep medullary portions of the LH
3. descending and ascending vessels; low

Question 7

(Countercurrent multiplication)

1. occurs where?
2. bulids up osmolaltiy gradient in what?

3-4. Two step process - what are they?

Answer 7

1. in loops of Henle
2. interstitial fluid
3. single effect
4. flow of tubular fluid

Question 8

(Single Effect)

1. Removes salt from thick ascending limb of the loop of Henle (TAL) and delivers it to what?

what reabsorbs salt?

driven by what?

2. TAL epitehlium impermeable to what?
3. what does this mean?

Answer 8

1. the interstitium

Na-K-2Cl cotransporter

Na-K ATPase

2. water
3. water cannot follow solute (separates salt and water)

Question 9

Answer 9

(Single Effect)