Which best describes the blood flowing in an artery?
a. it contains no red blood cells.
b. it is oxygen poor.
c. it moves away from the heart.
d. it contains no white blood cells.

Nephrons, the functional unit of kidneys, are responsible for formation of urine. the sentences describe situations that are the result of problems in the urine formation process. for the nephron shown below, match each situation to the step in the urine formation process where the problem lies.