Renal Functions, Basic Processes, and Anatomy
Chloride reabsorption parallels sodium reabsorption mainly because
a. chloride is almost always transported via a symporter with sodium.
b. chloride is the most abundant negatively charged species available to balance the reabsorption of the positive charge on sodium.
c. chloride has such a high passive permeability.
d. chloride and sodium are both part of the sodium chloride molecule and cannot be separated.
(b) Reabsorbed sodium must be balanced by reabsorbed anions. Once most of the bicarbonate is reabsorbed, only chloride exists in high enough concentration to match the continued reabsorption of sodium.
The obligatory water loss in the kidney
a. is another name for insensible loss of water.
b. occurs because there is always at least some excretion of waste solutes.
c. occurs because there is an upper limit to how fast aquaporins can reabsorb water.
d. is the amount of water that accompanies salt excretion.
(b) So long as there is filtration there is excretion of organic waste, which obligates water to be excreted also.
Which region of the tubule secretes water?
a. The descending thin limb.
b. The cortical collecting duct.
c. The medullary collecting duct (when ADH is absent).
d. No region secretes water.
(d) Osmotic conditions in all tubule regions favor water reabsorption.
If the thick ascending limb stopped reabsorbing sodium, then the final urine would be
a. iso-osmotic with plasma in all conditions.
d. dilute or concentrated, depending on ADH.
(a) The tubular fluid entering the medulla is iso-osmotic. If the tubules did not separate salt from water, the medullary interstitium would remain iso-osmotic. The luminal fluid would also remain iso-osmotic because there would be no tendency to either dilute it or concentrate it.
If a healthy young person drinks a large amount of water, which of the following is unlikely to happen?
a. An increase in medullary blood ...