Q 01/05

Roughly how long is an adult human kidney?

A) 6 cm

B) 12 cm

C) 20 cm

D) 25 cm

Answer · why

B) 12 cm

About the length of a smartphone; a Danish study measured a median of 11.2 cm on the left and 10.9 cm on the right.

Q 02/05

Which tube carries urine from each kidney to the bladder?

A) Ureter

B) Renal vein

C) Urethra

D) Collecting duct

Answer · why

A) Ureter

The urethra is the exit tube from the bladder; the two ureters feed it from above.

Q 03/05

What is the structural and functional unit of the kidney called?

A) Nephron

B) Alveolus

C) Neuron

D) Islet

Answer · why

A) Nephron

Each adult human kidney has around a million of them; a mouse kidney gets by with about 12,500.

Q 04/05

Approximately how many nephrons does each adult human kidney contain?

A) 10,000

B) 100,000

C) 1 million

D) 100 million

Answer · why

C) 1 million

By early chronic kidney disease that number is roughly halved, similar to the loss between young adulthood and one's seventies.

Q 05/05

What share of the heart's output flows through the kidneys in an adult?

A) About 5%

B) About 10%

C) About 20-25%

D) About 50%

Answer · why

C) About 20-25%

That is a huge share for two organs weighing a few hundred grams between them, which is why blood-pressure problems hit the kidneys hard.