ureters

The ureters are a pair of slender, muscular tubes that transport urine from the renal pelvis to the urinary bladder. In adults they measure about 25–30 cm in length and lie retroperitoneally along the psoas major, descending from the hila of the kidneys to the bladder.

Their course includes several important landmarks. Each ureter begins at the renal pelvis, descends retroperitoneally, crosses the pelvic brim at the bifurcation of the common iliac arteries, and enters the urinary bladder at the posterolateral wall. The uretero–vesical junction forms a mechanism that helps prevent reflux, with the ureter passing obliquely through the bladder wall. The narrowest point is at the ureterovesical junction.

Structurally, the ureter has a mucosal lining of transitional epithelium (urothelium) with a vascular lamina propria, followed by a muscularis externa consisting of an inner longitudinal layer and an outer circular layer, and an adventitia. It remains retroperitoneal along its length, lacking a serosal covering along most of its course.

Blood supply, innervation, and drainage are segmental. Arterial supply comes from renal, gonadal, common iliac, internal iliac, and superior vesical arteries along different segments. Lymphatics drain to lateral aortic and iliac nodes. Nerve supply derives from renal and aortic plexuses, with parasympathetic input from pelvic splanchnic nerves and sympathetic input contributing to regulation of peristaltic activity.

Functionally, the ureters use peristaltic contractions to propel urine from the kidneys to the bladder, aided by gravity. Clinically, obstruction by stones, strictures, or injury can cause flank pain, hydronephrosis, or urinary complications and may require imaging, intervention, or surgical management.