Which of the following is the functional unit of the kidney?

Cortical and juxtamedullary nephrons differ in the:

a. Lengths of their nephron loops

b. Structure of the capillaries surrounding them

c. Structure of their renal corpuscles

d. Both a and b are correct

e. Both b and c are correct

Explain why the filtrate becomes hypotonic as it flows through the ascending limb of the nephron loop. Also explain why the filtrate at the bend of the nephron loop (and the interstitial fluid of the deep portions of the medulla) is hypertonic.