Introduction to the Urinary Tract
The urinary tract, or system, consists of the kidneys, ureters, bladder,
and urethra. The kidneys are two bean-shaped organs located below
the ribs toward the middle of the back. The kidneys remove extra water
and wastes from the blood, converting it to urine. They also keep a
stable balance of salts and other substances in the blood.
The kidneys produce hormones that help build strong bones and help
form red blood cells.
Narrow tubes called ureters carry urine from the kidneys to the bladder,
an oval-shaped chamber in the lower abdomen. Like a balloon, the
bladder's elastic walls stretch and expand to store urine. They flatten
together when urine is emptied through the urethra to outside the body.
What is a kidney stone?
A kidney stone is a hard mass developed from crystals that separate from the urine and build up on the inner surfaces of the kidney. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. These inhibitors do not seem to work for everyone, however, so some people form stones. If the crystals remain tiny enough, they will travel through the urinary tract and pass out of the body in the urine without being noticed.
Kidney stones may contain various combinations of chemicals. The most common type of stone contains calcium in combination with either oxalate or phosphate. These chemicals are part of a person's normal diet and make up important parts of the body, such as bones and muscles.
