According to David Howes, M.D., writing in "Tintinalli's Emergency Medicine," urinary tract infections are the second most common type of infection in the United States. A healthy urinary tract has several important functions. It helps maintain a normal blood pressure and blood volume, saves nutrients and minerals, and eliminates waste products.
Renal Pelvis
As the kidneys make urine, it collects within the kidneys in structures called the calices. The urine then drains from the calices to the renal pelvis. According to "Smith's General Urology," the renal pelvis in some people is completely within the kidney. But in others, only some of the pelvis lies within the kidney; the rest is partially outside of the kidney. In either case, the pelvis narrows and becomes the ureter.
Ureters
Urine passes from the renal pelvis to the ureters. As explained by "Current Diagnosis & Treatment: Surgery," the ureter is a muscular tube that connects the renal pelvis (of each kidney) to the bladder. Each ureter is actually composed of three layers. The middle layer has smooth muscle. Approximately every 30 seconds, the muscle contracts and then relaxes to push the urine from the renal pelvis to the urinary bladder.
Urinary Bladder
The urinary bladder is the organ that temporarily stores the urine. "Fundamentals of Anatomy & Physiology" states that the bladder can store approximately 35 oz. of urine. In the lower part of the bladder, there is a triangular area called the trigone. Each ureter drains into the bladder in this trigone area. Urine leaves the bladder from the trigone area through the urethra. The opening to the urethra is in the trigone. Like the ureters, the bladder has three layers. One of the layers is smooth muscle. The muscle is very strong, and when it contracts, the whole bladder is compressed and the urine leaves through the urethra.
Urethra
The urethra is the final component of the urinary tract. Urine enters the urethra at the trigone area of the bladder, then passes through the urethra to exit the body. Its length is much shorter in a woman than in a man. The female urethra is approximately 1 to 2 inches long; the male urethra is 7 to 8 inches, because it starts at the trigone of the urinary bladder and ends at the tip of the penis.
References
- "Current Diagnosis & Treatment: Surgery"; Gerard Doherty, M.D.; 2010
- "Fundamentals of Anatomy & Physiology"; Frederic Martini, Ph.D.; 1995
- "Smith's General Urology"; Emil Tanagho, M.D., Jack McAninch, M.D.; 2008
- "Tintinalli's Emergency Medicine: A Comprehensive Study Guide"; Judith Tintinalli, M.D., Gabor Kelen, M.D., et al.; 2004
