Kidney Anatomy
Human kidneys are paired, reddish brown, bean shapped structures about 11 cm (4.4 in) long and function as excretory system . They are located in back of the body cavity, one on each side of the spine just above the waist. The kidneys are loosely held in place by a mass of fat and by fibrous tissue. The outer margin is convex, the inner border concave. On the inner surface is a slit, the hilus, through which pass the arteries, veins, nerves and the renal pelvis, a funnellike structure. Urine from each kidney is collected in the renal pelvis and passes into the hollow tube, the ureter, which extends downward, emptying into the urinary bladder. A shorter, single tube, the urethra, eliminates urine the bladder. The cut surface of the kidney reveals two distinct areas; the cortex - a dark band along the outer border, about 1 cm (0.4 in) thickness, and the inner medulla. The medulla is divided into 8 to 18 conical tissues termed renal pyramids (cortical arches) and extends down between e