The Human Body

Urinary System

Urinary System, system of organs that produces and excretes urine from the body. Urine is a transparent yellow fluid containing unwanted wastes, mostly excess water, salts, and nitrogen compounds. The major organs of the urinary system are the kidneys, a pair of bean-shaped organs that continuously filter substances from the blood and produce urine. Urine flows from the kidneys through two long, thin tubes called ureters. With the aid of gravity and wavelike contractions, the ureters transport the urine to the bladder, a muscular vessel. The normal adult bladder can store up to about 0.5 liter (1 pt) of urine, which it excretes through the tubelike urethra.

An average adult produces about 1.5 liters (3 pt) of urine each day, and the body needs, at a minimum, to excrete about 0.5 liter (1 pint) of urine daily to get rid of its waste products. Excessive or inadequate production of urine may indicate illness and doctors often use urinalysis (examination of a patient’s urine) as part of diagnosing disease. For instance, the presence of glucose, or blood sugar, in the urine is a sign of diabetes mellitus; bacteria in the urine signal an infection of the urinary system; and red blood cells in the urine may indicate cancer of the urinary tract.

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Related topic: Urinary System of the Animals