Ureter

In human anatomy, the ureters are the ducts that carry urine from the kidneys to the urinary bladder, passing anterior to the psoas major. The ureters are muscular tubes that can propel urine along by the motions of peristalsis. In the adult, the ureters are usually 25-30cm long.

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In humans, the ureters enter the bladder through the back, running within the wall of the bladder for a few centimetres. The backflow of urine is prevented by valves known as ureterovesical valves, pressure from the filling of the bladder, and the tone of the muscle in the bladder wall.

In the female, the ureters pass through the mesometrium on the way to the urinary bladder.

Histology

  The ureter has a diameter of about 3 millimeters, and the lumen is star-shaped. Like the bladder, it is lined with transitional epithelium, and contains layers of smooth muscle.

The epithelial cells of the ureter are stratified (in many layers), are normally round in shape but become squamous (flat) when stretched. The lamina propria is thick and elastic (as it is important that it is impermeable).

There are two spiral layers of smooth muscle in the ureter wall, an inner loose spiral, and an outer tight spiral. The inner loose spiral is sometimes described as longitudinal, and the outer as circular, (this is the opposite to the situation in the gastrointestinal tract). The distal third of the ureter contains another layer of outer longitudinal muscle.

The adventitia of the ureter, like elsewhere is composed of fibrous connective tissue, that binds it to adjacent tissues.

Diseases and disorders

Medical problems that can affect the ureter include:

• cancer of the ureter
• passage of kidney stones
• ureterocele
• megaureter
• vesico-ureteric reflux
• anatomical abnormalities, such as duplexing and ectopia.

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