Urine passes through the body from the kidneys to the bladder, which empties through the urethra, according to the National Institutes of Health. The kidneys filter up to 150 quarts of blood to produce 1 to 2 quarts of urine each day.
The urinary tract drains the body of wastes and extra fluid. The kidneys are two bean-shaped organs located on each side of the spine, just below the rib cage, states the National Institutes of Health. Urine passes from the kidneys through two thin tubes of muscle located on each side of the bladder, called ureters.
The bladder, located between the pelvic bones, expands as it fills with urine. A normal bladder can hold 1.5 to 2 cups of urine, explains the National Institutes of Health. As it fills, the bladder sends a signal to the brain saying it is time to urinate. During urination, the brain signals the muscles in the bladder wall to tighten and squeeze the urine out. Muscles surrounding the urethra, known as internal and external sphincters, relax at the same time, allowing the urine to exit from the bladder through the urethra.
Urinary tract infections, or UTIs, occur when bacteria travels up the urethra, into the bladder and the kidneys, notes WebMD. Women are especially vulnerable to UTIs because they have shorter urethras. Urinating after sex and wiping from front to back can help minimize the risk of UTIs, which are treated with antibiotics.