The urinary system eliminates waste products from the body and helps regulate the body’s water and chemical balance. The organs of the urinary system include two oval-shaped kidneys, each with a long, slender tube, called the ureter, that connects to the bladder. Another tubular vessel, the urethra, extends from the bladder to an opening out of the body.
The kidneys are the major excretory organs of the body. As the body’s blood flows through the kidneys, microscopic tubules called nephrons remove urea, salts, and other poisonous waste products formed during metabolism. The kidneys produce urine to carry away these waste products.
Nephrons also selectively absorb proteins, salts, sugar, calcium, and other nutrients. The kidneys return these life-sustaining substances to the bloodstream to maintain a healthy blood composition. The kidneys also secrete hormones that regulate body functions such as blood pressure and the production of red blood cells.
Urine is produced in the kidneys and travels through the ureters to the bladder, a muscular sac that stores the urine. When the bladder is full, nerves signal the bladder to contract and expel urine from the body through the urethra.