Your Body - Anatomy of the Urinary System
How does the urinary system work?
The body takes nutrients from food and converts them to energy. After the body has taken the food that it needs, waste products are left behind in the bowel and in the blood.
The urinary system keeps chemicals, such as potassium and sodium, and water in balance, and removes a type of waste, called urea, from the blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys, where it is removed.
Urinary system parts and their functions:
- two kidneys - a pair of purplish-brown organs located below the ribs toward the middle of the back. Their function is to:
- remove liquid waste from the blood in the form of urine.
- keep a stable balance of salts and other substances in the blood.
- produce erythropoietin, a hormone that aids the formation of red blood cells.
- regulate blood pressure.
- two ureters - narrow tubes that carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.
- bladder - 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 relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours.
- two sphincter muscles - circular muscles that help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder.
- nerves in the bladder - alert a person when it is time to urinate, or empty the bladder.
- urethra - the tube that allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs.
Facts about urine:
- Adults pass about a quart and a half of urine each day, depending on the fluids and foods consumed.
- The volume of urine formed at night is about half that formed in the daytime.
- Normal urine is sterile. It contains fluids, salts and waste products, but it is free of bacteria, viruses and fungi.
- The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.
Click here to view the
Online Resources of Women's Center
Disclaimer - This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional evaluation, advice, diagnosis or treatment by a healthcare professional. © 2009 Staywell Custom Communications.