a. Urine is formed by the kidneys in millions of tiny filtration plants called
nephrons. The nephrons receive and filter all the blood in the body about once every 12
b. Each nephron (figure 2-3) is composed of 3 parts: the glomerulus, the
capsule, and the tubule. Each part is essential in the filtration, re-absorption, and
Figure 2-3. The kidney nephron.