CBM self tests

Question 1

The transitional epithelium:

Answer 1

Lines the ureters and the bladder.
The transitional epithelium (aka urothelium) is a 3-layered epithelium lining the ureters and the bladder. It contains low-permeability luminal cells, preventing the dissipation of the urine-plasma gradient.

Question 2

A raised plasma concentration of which of the following substances would provide the best indication of a lowered GFR ?

Answer 2

Creatinine
Creatinine (not creatine) clearance provides a reasonable (not precise) measurement of GFR because it is freely filtered and there is little reabsorption or secretion thereafter. To maintain an excretion rate that matches its rate of production will require a rise in plasma concentration when GFR falls. Urea is a much less accurate marker. inine

Question 3

For which of the following will the concentration in tubular fluid at the end of the proximal tubule be markedly higher than the plasma concentration ?

Answer 3

Creatinine

Question 4

In which of the following nephron segments is the triple co-transporter (Na+K+2Cl-) particularly important?

Answer 4

Thick ascending limb of the loop of Henle

Question 5

In which of the following nephron segments is there believed to be little or no active Na+ transport across the wall of the tubule ?

Answer 5

Descending limb of the loop of Henle

Question 6

In which of the following nephron segments is the main route by which Na+ enters the cell via Na+ channels?

Answer 6

There are sodium channels elsewhere but in the earlier segments of the nephron other routes of entry are more important.

Cortical collecting duct principal cells

Question 7

Vasopressin:

Answer 7

This is achieved through the insertion of aquaporins in the luminal membranes of the principal cells of the collecting duct.
Lecture on water.

Question 8

Diabetes insipidus:

Answer 8

Cranial refers to a problem in ADH release, and nephrogenic refers to a problem in the ADH receptor.

Can be cranial or nephrogenic

Question 9

During a water diuresis, in which of the following nephron segments will the tubular fluid osmolarity be highest?

Answer 9

Countercurrent multiplication ensures a high osmolarity at the tip of the loop even during a maximal water diuresis .

Question 10

During a water diuresis, in which of the following nephron segments will the tubular fluid osmolarity be lowest?

Answer 10

The medullary collecting duct

The fluid emerging from the loop will be hypo-osmolar but since the water permeability of all later segments of the nephron will be very low, further solute reabsorption will lower osmolarity still further as the tubular fluid passes along the distal convoluted tubule and collecting duct.

Question 11

During a maximal antidiuresis (i.e. the production of the most concentrated possible urine), in which of the following nephron segments will the tubular fluid osmolarity be lowest?

Answer 11

Even during a maximal antidiuresis the fluid emerging from the loop will be hypo-osmolar. As the fluid passes through the water permeable collecting ducts tubular fluid osmolarity will rise as water is reabsorbed.