Ureter

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.

Structure

In humans, the ureters arise from the pelvis of each kidney, and descend on top of the psoas major muscle to reach the brim of the pelvis. Here, they cross in front of the common iliac arteries. They then pass down along the sides of the pelvis, and finally curve forwards and enter the bladder from its left and right sides at the back of the bladder. This is classically depicted as running "posteroinferiorly on the lateral walls of the pelvis and then curve anteromedially to enter the bladder". The junction between the pelvis of the kidney and the ureters is known as the pelvoureteric junction and the junction between the ureter and the bladder as the vesicoureteric junction. At the entrance to the bladder, the ureters are surrounded by valves known as ureterovesical valves, which prevent the backflow of urine.