ureter /yo͝or″ətər, yo͝orē″tər/ [Gk, oureter] , one of a pair of tubes, about 30 cm long, that carries urine from the kidney into the bladder. Each tube is composed of a fibrous, a muscular, and a mucous coat and divides into an abdominal part and a pelvic part. The abdominal part lies behind the peritoneum on the medial side of the psoas major and enters the pelvic cavity by crossing either the termination of the common iliac artery or the commencement of the external iliac artery. In men the pelvic part of the ureter runs caudally along the lateral wall of the pelvic cavity and reaches the lateral angle of the bladder just ventral to the upper tip of the seminal vesicle. In women the pelvic part of the ureter forms the posterior boundary of the ovarian fossa and runs medially and ventrally along the upper part of the vagina. The ureter enters the bladder through a tunnel that functions as a valve to prevent backflow of urine into the ureter when the bladder contracts. Connecting with the kidneys, the ureters expand into funnel-shaped renal pelves that branch into calyces. Urine is pumped through the ureters by peristaltic waves that occur an average of three times a minute. −ureteral, adj.
