Harnleitern

Harnleitern, or ureters, are two muscular tubes that transport urine from the renal pelvis to the urinary bladder. In adults each ureter is about 25 to 30 cm long. They descend retroperitoneally along the psoas major, cross the bifurcation of the common iliac arteries, and enter the bladder at the ureterovesical junction, where an oblique course helps prevent reflux.

The ureter wall comprises a mucosa lined by transitional epithelium, a middle muscularis with inner circular and outer longitudinal layers, and an outer adventitia. Blood supply is segmental: proximal by branches of the renal arteries, middle by gonadal or common iliac arteries, and distal by vesical arteries. Lymphatic drainage goes to lumbar and iliac nodes. Autonomic innervation from renal and pelvic plexuses modulates peristalsis.

Functionally, the ureters generate peristaltic waves that move urine toward the bladder, typically in response to distension and flow. The ureterovesical junction acts as a one-way valve to limit reflux; urine enters the bladder as intravesical pressure rises and the detrusor muscle relaxes during filling and voiding.

Developmentally, the ureters arise from the ureteric bud of the mesonephric duct during embryogenesis and connect to the metanephros to form the renal collecting system. Clinically, obstruction, stones, or congenital strictures can cause hydronephrosis and flank pain. Imaging options include ultrasound and CT urography; treatment ranges from observation to ureteral stenting, ureteroscopy with lithotripsy, or reconstructive surgery for obstructive lesions.