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(yo͝orē`tər), thick-walled tube that conveys urine from the kidneykidney, artificial,
mechanical device capable of assuming the functions ordinarily performed by the kidneys. In treating cases of kidney failure a tube is inserted into an artery in the patient's arm and blood is channeled through semipermeable tubes immersed in a bath
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 to the urinary bladder. It is approximately 10 in. (25.4 cm) long, with the upper half located in the abdomen and the lower half in the pelvic region. Urine is transported down this tube under the impetus of gravity assisted by contractions of the smooth muscles that line the ureteral walls. A blocked ureter can result from congenital abnormality, a tumor, or the formation of kidney stones. Blockage may require surgery to prevent loss of urinary function and eventual urea poisoning. See urinary systemurinary system,
group of organs of the body concerned with excretion of urine, that is, water and the waste products of metabolism. In humans, the kidneys are two small organs situated near the vertebral column at the small of the back, the left lying somewhat higher than the
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the efferent duct that serves to remove the urine from the kidney.

During the embryonic development of many vertebrates, the excretory function is fulfilled by three successive forms of kidney: the pronephros (also called the primordial kidney or the forekidney), the mesonephros (also called the middle kidney), and the metanephros—the definitive, permanent kidney. Correspondingly, three types of ureter arise: the pronephric duct, the mesonephric duct (also called Wolffian duct), and the metanephric duct—the definitive, permanent ureter.

The pronephric ducts continue to function past the embryonic stage only in cyclostomes, in which the ducts open into the urogenital sinus. In fish and amphibians, the Wolffian ducts continue to function as ureters throughout postembryonic life. In certain fish—dipnoans, chondrosteans, and holosteans—and in male amphibians, the ureters also function as the deferent ducts. The mesonephric ducts of fish open to the exterior of the body either directly through the urinary orifice (in all female teleosts and in the males of a few teleost species), through the urogenital sinus (in elasmobranchs, holocephalans, chondrosteans, holosteans, Polypterus, and most male teleosts), or through the cloaca (in chondrichthians and dipnoans). In most teleosts, the ureters empty into the urinary bladder. The metanephric ducts are the postembryonic ureters of reptiles, birds, mammals, and man; in all these, the sole function of the ureter is to conduct urine. In birds, monotremes, and most reptiles, the ureters empty into the cloaca, while in metatherians, viviparous mammals, certain reptiles, and man, they empty into the urinary bladder.

In man the two ureters are tubular organs through which urine flows from the kidneys into the urinary bladder. The ureters are situated on the posterior wall of the abdominal cavity on both sides of the spinal column. On the average, each ureter is 30–35 cm long and 7–9 mm at its widest diameter. The ureters are internally lined with mucosa. Smooth muscles in the walls of the ureters ensure the flow of urine to the urinary bladder, regardless of the position the body is in.

Urethritis—inflammation of the ureteral mucosa—is the commonest disease of the ureters. Kidney stones can pass through the ureters, causing injury to the ureteral linings. Occasionally, one or both ureters can be congenitally bifurcated at the site of emergence from the kidney; complete doubling of one or both ureters is also possible. Other developmental anomalies include prolapse of the ureter into the vagina (in women) or into the seminal vesicles (in men).


A long tube conveying urine from the renal pelvis to the urinary bladder or cloaca in vertebrates.


the tube that conveys urine from the kidney to the urinary bladder or cloaca
References in periodicals archive ?
Case Report: a Clinical Approach in a Dog with Unilateral and Intramural Ectopic Ureter with Combined Surgical Techniques
1) Ectopic ureter draining into the genital system is a rare entity and results from a more cranial origin of the ureteral bud from the mesonephric duct with resultant ureteral stump opening in the mesonephric duct derivatives (seminal vesicles, ejaculatory ducts, or vas deferens).
Primary large cell neuroendocrine carcinoma of the ureter.
sup][1] An anastomosis of allograft pelvis to native ureter has been reported to be a treatment for donor kidney with UPJO at initial transplantation;[sup][2] however, few studies focused on the surgical option for urinary tract reconstruction of donor kidney with UPJO in re-transplantation.
An attempt was made to select the left internal iliac artery, and then contrast was injected which demonstrated the catheter to be in the left ureter instead of the left internal iliac and the arteriogram demonstrated brisk flow of contrast into the left ureter, confirming the presence of an internal iliac arterioureteral fistula (Figure 2).
When the ureteric bud prematurely divides before penetrating the metanephric blastema, this results in an incomplete duplex with ureters that meet before the bladder or a bifid renal pelvis.
Intravenous pyelography has vital role not only clearly demonstrating duplex pelvi-calyceal system and ureters but also clearly documenting the sparing of upper pole moiety parenchyma and pelvi-calyceal system as well as pelvi-calyceal system of lower moiety as compared to CT scan because of large tumor overlap with renal parenchyma on CT scan.
The search terms used were 'fibro-epithelial OR fibroepithelial AND ureter OR ureteral.
On unenhanced CT scans, retroperitoneal fibrosis appears as a plaque that is isodense with muscle and that envelops the aorta and inferior vena cava between the renal hila and sacral promontory and usually extends laterally to incorporate the ureters.
Follow-up for the patients posttreatment of 3-4 months showed the normal ureters with no obstruction or stricture by intravenous pyelography after removing the double J stent.