Identify the role of the urinary system in acid-base balance: 1. The kidneys can
ID: 3517500 • Letter: I
Question
Identify the role of the urinary system in acid-base balance:
1. The kidneys can secrete bicarbonate ions when the pH of the blood rises.
2. The kidneys contribute to acid-base balance by excreting fixed acids that the lungs cannot excrete.
3. The kidneys can manufacture new bicarbonate ions when the pH of the blood falls.
4. The kidneys contribute to acid-base balance by controlling the concentration of bicarbonate ions in the blood.
a. 1, 2, 3, but not 4
b. 2, 3, 4, but not 1
c. 1, 3, 4, but not 2
d. 1, 2, 3, and 4
Explanation / Answer
d : 1, 2 , 3 , 4
If urine pH < 6, the concentration of HC0
3- in the urine is very low (e.g.< 0.1 mEq/L). The glomerular ultrafiltrate has 24 mM. Thus, most HC03- filtered (4500 mEq/day) is reabsorbed, mostly (90%) along the proximal tubules.