The ureters are thin paired muscular tubes that connect the kidneys (Read more!) with the urinary bladder (Read more!). They collect and transport urine from the renal pelvis (Read more!) to the bladder. Each ureter enters the urinary bladder posterolaterally via the opening called the ureteral orifice.

The ureters appear more or less s-shaped and are approximately 0.12 to 0.16 inches (3 - 4 mm) in diameter and around 9.84 to 11.81 inches (25 - 30 cm) in length. The wall of the ureter is very muscular (it is composed of three muscle layers), and these muscle cells provide the peristaltic activity that moves the urine from the kidneys to the urinary bladder. The ureters are retroperitoneal structures.

Each ureter is a continuation of the renal pelvis. In fact, the renal pelvis is the funnel-shaped flattened upper end of each ureter. The site between the ureter and renal pelvis is known as the ureteropelvic junction. From the junction, each ureter passes downward and goes along the posterior wall of the abdominal cavity.

The ureters pass through both the abdominal and pelvic cavities. Within the abdominal cavity, they descend, lying on the psoas major muscles (Read more!). The ureters usually enter the lesser pelvis at the iliac bifurcations (Read more!). Each ureter crosses either the common iliac artery (Read more!) or the beginning of the external iliac artery (Read more!) at the level of the sacroiliac joint. They can also be found within the cleft formed by both iliac arteries. Note that this is one of the few locations where these structures are fixed in place.

The ureters enter the pelvic brim at an acute angle. Once the ureter enters the lesser pelvis, it descends further, first traveling in the posterolateral direction along the anterior aspect of the greater sciatic notch (Read more!). When it reaches the ischial spine (Read more!), it turns in the anteromedial direction to reach the urinary bladder. The site at which the ureter connects with the urinary bladder is known as the ureterovesical junction.

In men, the ureter passes posterior to the ductus deferens (Read more!) and anterior to the superior portion of the seminal vesicle (Read more!) before it enters the urinary bladder. In women, the ureters go posterior to the ovaries and fallopian tubes. They also travel close to the uterine arteries (the distance is approximately 0.98 inches (2.5 cm)), which are found anterior to them. Before the female ureter enters the urinary bladder, it goes adjacent to the cervix.

While the ureters are descending, they are also related to various neurovascular structures. For instance, they cross over the genitofemoral nerves on their way to the urinary bladder, as the genitofemoral nerves lie on the psoas major muscles. In contrast, the gonadal vessels (testicular or ovarian vessels) travel anterior to the ureters.

Note: The ureter goes through the wall of the urinary bladder in an oblique manner. This creates an antireflux mechanism, preventing urine from flowing back into the ureter during detrusor muscle contractions.

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Ureters