What are the functions of the kidneys, ureters and bladder?
The kidneys are bean-shaped organs, each about the size of a fist. They are located near the middle of the back, just below the rib cage, one on each side of the spine. The kidneys are sophisticated reprocessing machines. Every day, a person’s kidneys process about 200 quarts of blood to filter out about 2 quarts of waste products and extra water. The wastes and extra water become urine, which flows to the bladder through tubes called ureters. The kidneys also produce hormones and are responsible for acid/base balance in the body.
The ureters are narrow tubes that carry urine from the kidneys to the bladder. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters. Muscles in the walls of the ureter continually tighten and relax forcing urine downward, away from the kidneys.
The bladder stores urine until releasing it through urination. The bladder is a triangle-shaped, hollow organ located in the lower abdomen. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder’s walls (detrusor muscle) relax and expand to store urine, and contract and flatten to empty urine through the urethra.
The urethra is a tube which connects the urinary bladder to the outside of the body, and carries semen in men, and urine in women and men. In females, the urethra is shorter and emerges above the vaginal opening.
The external urethral sphincter is a muscle that allows voluntary control over urination.