Part 1 of Essay
In vertebrates, are the two major organs of excretion. Excess water, toxic waste products of metabolism such as urea, uric acid, and inorganic salts are disposed of by in the form of urine. are also largely responsible for maintaining the water balance of the body and the pH of the blood. Kidneys play important roles ....

Part 2 of Essay
.... cut surface of the kidney reveals two distinct areas: the cortex- a dark band along the outer border, about one centimeter in thickness, and the inner medulla. The medulla is divided into 8 to 18 cone-shaped masses of tissue named renal pyramids. The apex of each pyramid, the papilla, extends into the renal pelvis, through which urine is released from the kidney tissue. The cortex arches over the bases of the pyramids (cortical arches) and extends down between each pyramid as the renal columns. Urine passes t ....