The major function of the urinary system is elimination of excess water, excess chemicals and waste products.
The kidneys are situated in the area of the middle back on either side of the spine. Each kidney is bean shaped and is about 4 inches (10 cm) long. The right kidney sits a little lower than the left.
The function of the kidneys is to eliminate wastes and to keep a certain level of water and chemicals in the body constant. If the water level is too high, such as after you drink a lot, the kidneys will excrete a lot of urine, and it will look pale and diluted. If the water level is too low, when you don't drink enough, the kidneys will excrete less water causing the urine to be darker and more concentrated.
Blood enters the kidneys through the renal artery after the body has taken what it needs for energy and repair and is filtered through units called nephrons. Each kidney contains about a million nephrons, where waste materials, both solid and liquid are eliminated from the blood before it returns to the rest of the body.
The ureters are narrow muscular tubes, about 10 inches (25 cm) long, which drain the urine into the bladder from the kidneys.
The bladder is a muscular sac that serves as a reservoir for the urine. A muscular ring called the sphincter surrounds the exit from the bladder into the urethra and it prevents urine from flowing out of the bladder when contracted.
The urethra is a muscular tube about an inch and-a-half long (in men it is about 8 inches long). It leads from the bladder to the exterior and it is along this tube that urine leaves the body.
The average person passes about a liter and a half of urine a day and about half that amount nightly. The volume varies depending on the fluids and foods consumed.
Urine and urination are among the best ways to diagnose disorders, not just in the urinary system but in the whole body. Changes in quantity, frequency, the inability to restrain or control, pain, or other unusual sensations related to urination may need the attention of a doctor.
Characteristics of urine that may call for a doctor's attention are change in color, odor, cloudiness, or content. But these characteristics can also appear in healthy urine due to reasons such as drinking too many liquids, eating certain foods (beets, for example, cause urine to be reddish in color), or from medicines that discolor or cloud it.
In any case, if you have the slightest suspicion that you might have a urinary problem, play it safe and consult your doctor immediately.
The prevalence of urinary disorders increases with age. Every part of the urinary system can be affected by aging:
Common urinary disorders among women baby boomers include: