Ureter

Dr. Manuela Mai studied medicine at the Universities of Heidelberg and Mannheim. After graduating, she gained clinical experience in gynecology, pathology and clinical pharmacology. She is particularly interested in the broader connections that lead to diseases - also outside of conventional medicine. She completed additional training in classical homeopathy as well as ear and skull acupuncture.

More about the experts All content is checked by medical journalists.

The urine from the renal pelvis enters the urinary bladder through the ureter (ureter). Each kidney has its own ureter. Here you can read everything you need to know about this tubular part of the lower urinary tract: structure, function and common diseases and injuries of the ureter.

What is the ureter?

Ureter is the medical term for the ureter. Each kidney has a ureter through which the urine is transported: the renal pelvis in each kidney narrows downwards towards the tubular ureter.

The two ureters are each two to four millimeters thick and 24 to 31 centimeters long. They pull down behind the peritoneum (retroperitoneal) and open into the urinary bladder.

course

Each ureter is divided into two sections:

The part after the calyx is the pars abdominalis. The lower part that opens into the urinary bladder is called the pars pelvetica. The two parts of the ureter show no functional differences; the division is purely for anatomical reasons.

During its course, the ureter shows three constrictions, which are called upper, middle and lower constrictions:

The upper narrow is at the transition from the renal pelvis to the ureter.
The middle narrow is formed by the crossing with the pelvic artery (Arteria iliaca externa).
The lower narrowing occurs when the ureter passes through the wall of the urinary bladder.

The point where the ureter joins the urinary bladder is woven into the bladder wall in such a way that it acts as a valve. In addition, the mouth is actively closed by muscles, which also prevents the backflow of urine from the bladder into the ureter.

Structure of the ureteral wall

A cross-section through a ureter shows a star-shaped interior and a four-layer wall structure. From the inside out there are the following layers:

Tunica mucosa, consisting of the urothelium and lamina propria
Tunica muscularis
Tunica adventitia

The tunica mucosa (layer of mucous membrane) consists of a special cover and glandular tissue (urothelium) and a layer of connective tissue (lamina proporia) underneath. The urothelium is very resistant to the influences of urine and its cells are particularly tightly connected to one another (via "tight junctions"). This prevents urine from entering the space between the cells (intercellular space).

The lamina propria (connective tissue layer) is responsible for the star shape of the ureter interior (lumen) by forming longitudinal folds. In this way, the inner wall of the ureter can nestle against one another, but the lumen can unfold during urine transport.

The tunica muscularis (muscle layer) is a strong layer of smooth muscle. It generates peristaltic waves and thus ensures the active transport of urine through the ureter towards the urinary bladder.

The tunica adventitia (connective tissue) is used to build the ureter into the surrounding connective tissue. In addition, the supplying blood vessels and nerves run here.

What is the function of the ureter?

The function of the ureter is to transport urine from the kidney to the urinary bladder. The smooth muscles of the tunica muscularis contract in such a way that a so-called peristalsis arises - wave-like movements that always move the urine towards the urinary bladder, even against a gradient. So it is possible that the urine always flows away from the kidneys towards the urinary bladder, even if the position of the body means that the urinary bladder is higher than the kidneys.

The peristaltic wave passes through the ureter several times a minute and is strong enough to force the urine through the constrictions.

If the urinary bladder empties while urinating, the ureter is automatically occluded by embedding the end of the ureter in the muscles of the urinary bladder. The urine cannot flow from the bladder back through the ureter towards the kidney.

Where is the ureter located?

The ureter begins in each kidney at the renal pelvis, at the level of the 2nd lumbar vertebra, and lies along its entire length outside the abdominal cavity (retroperitoneal). In its upper section (pars abdominalis) the ureter runs along the lumbar muscle (musculus psoas), between its fascia and the peritoneum. From the border with the small pelvis one speaks of the pars pelvetica of the ureter.

In their course, the ureters cross under and over several blood vessels and are on the left in the vicinity of the abdominal main artery (aorta abdominalis) and on the right to the inferior vena cava (inferior vena cava).

The ureters finally pull up to the urinary bladder from behind and pass through the wall at an oblique angle.

What problems can the ureter cause?

If problems occur in the area of the ureter, the urine transport is disturbed or the urine flows back towards the kidneys.

Ureteral colic

If deposits form in the kidney, they are called kidney stones. They can get into the ureter and get caught in the constrictions. By increasing muscle contractions in the ureter wall, the body tries to transport the kidney stones through the constrictions. These spasmodic muscle contractions and the stretching of the ureter wall are extremely painful and are known as colic.

Tumors

Various benign or malignant tumors can develop in the area of the ureters.

Malformations

The ureters often show malformations. These can appear as ureter enlargements (dilatations), constrictions (stenoses) or occlusions (atresia). There are also protrusions of the ureter wall (diverticulum).

Reflux

If the ureter enlarges or the closure mechanism at the transition to the urinary bladder is disturbed, urine may continue to flow back into the ureter. This allows bacteria from the urinary bladder to ascend into the ureter and on to the kidney. The possible consequences are inflammation of the ureter and renal pelvis.