|Ureter (Schematic View)|
|1. Human urinary system: 2. Kidney, 3. Renal pelvis, 4. Ureter, 5. Urinary bladder, 6. Urethra. (Left side with frontal section), 7. Adrenal gland|
8. Renal artery and vein, 9. Inferior vena cava, 10. Abdominal aorta, 11. Common iliac artery and vein
12. Liver, 13. Large intestine, 14. Pelvis
In human anatomy, the ureters are tubes made of smooth muscle fibers that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually 25–30 cm (10–12 in) long and ~3-4 mm in diameter. Histologically, the ureter contains transitional epithelium and an additional smooth muscle layer in the more distal one-third to assist with peristalsis.
In humans, the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle. The ureters cross the pelvic brim near the bifurcation of the iliac arteries (which they cross anteriorly). This is a common site for the impaction of kidney stones (the others being the ureterovesical valve, where the ureter meets the bladder, and the pelvouteric junction, where the renal pelvis meets the ureter in the renal hilum). The ureters run posteroinferiorly on the lateral walls of the pelvis and then curve anteriormedially to enter the bladder through the back, at the vesicoureteric junction, running within the wall of the bladder for a few centimetres. The backflow of urine is prevented by valves known as ureterovesical valves.
In females, the ureters pass through the mesometrium and under the uterine arteries on the way to the urinary bladder. An effective phrase for remembering this anatomical relationship is "water (ureters) under the bridge (uterine arteries or vas deferens)."
Ureters are also found in all other amniote species, although different ducts fulfill the same role in amphibians and fish.
Cancer of the ureters is known as ureteral cancer.
A kidney stone can move from the kidney and become lodged inside the ureter, which can block the flow of urine, as well as cause a sharp cramp in the back, side, or lower abdomen. The affected kidney could then develop hydronephrosis, should a part of the kidney become swollen due to blocked flow of urine. There are three sites where a kidney stone will commonly become stuck:
- at the ureteric junction of renal pelvis;
- as the ureter passes over the iliac vessels;
- where the ureter enters into the urinary bladder (vesicoureteric junction).
The ureter is sometimes injured during hysterectomies, near the infundibulopelvic (suspensory) ligament or where the ureter courses posterior to the uterine vessels.
The ureters are supplied by multiple arteries. Most important is that these arteries approach the ureter from the medial side superior to the common iliac and from the lateral side inferior to the common iliac. The medial vessels can arise from the renal, gonadal, aorta, or common iliac while those approaching from the lateral can arise from the internal iliac and its branches such as the vesical, uterine, middle rectal, and vaginal arteries. Within the periureteral adventitia these arteries extensively anastomose thus permitting surgical mobilization of the ureter without compromising the vascular supply as long the the adventitia is not stripped. Lymphatic and venous drainage mostly parallels that arterial supply.
Frontal section through the kidney
Ultrasound demonstration of ureteral jet effect
Doppler ultrasound image ureteric jet effect inside urinary bladder.
Transverse section of human embryo eight and a half to nine weeks old
Tail end of human embryo thirty-two to thirty-three days old
The relations of the viscera and large vessels of the abdomen (seen from behind, the last thoracic vertebra being well raised)
The posterior surfaces of the kidneys, showing areas of relation to the parietes
Transverse section of ureter
Fundus of the male bladder with the vesiculæ seminales
Median sagittal section of male pelvis
Microscopic view of dog ureter
Ureters and other common iliac vessels