What is the ureter?
Ureter is the medical term for the ureter. Each kidney has a ureter through which urine is transported: The renal pelvis in each kidney narrows downward to form the tubular ureter.
The two ureters are each two to four millimeters thick and 24 to 31 centimeters long. They descend behind the peritoneum (retroperitoneally) and open into the urinary bladder.
Course
Each ureter is divided into two sections:
The part after the renal calyx is the pars abdominalis. The lower part, which opens into the urinary bladder, is called the pars pelvetica. The two parts of the ureter do not show any functional differences, the division is done purely on anatomical grounds.
During its course, the ureter shows three constrictions, called upper, middle and lower constriction:
- The superior constriction is located at the junction of the renal pelvis and the ureter.
- The middle constriction is formed by crossing with the iliac artery (Arteria iliaca externa).
- The inferior constriction is formed when the ureter passes through the wall of the urinary bladder.
The junction of the ureter with the urinary bladder is woven into the bladder wall in such a way that it acts as a valve. In addition, the orifice is actively closed by muscle, which further prevents the backflow of urine from the urinary bladder into the ureter.
Structure of the ureteral wall
- Tunica mucosa, consisting of urothelium and lamina propria
- Tunica muscularis
- Tunica adventitia
The tunica mucosa (mucosal layer) consists of a special covering and glandular tissue (urothelium) and an underlying connective tissue layer (lamina proporia). The urothelium is very resistant to the effects of urine and its cells are particularly firmly connected to each other (via “tight junctions”). Thus, urine cannot penetrate into the space between the cells (intercellular space).
The lamina propria (connective tissue layer) is responsible for the star shape of the ureteral interior (lumen) by forming longitudinal folds. This allows the inner wall of the ureter to nestle together, but the lumen to unfold during urine transport.
The tunica muscularis (muscular layer) is a powerful 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) serves to integrate 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 peristaltic wave passes through the ureter several times a minute and is powerful enough to force the urine through the constrictions.
When the urinary bladder empties during urination, automatic closure of the ureter occurs due to the embedding of the ureteral end in the muscles of the urinary bladder. Thus, urine cannot flow from the urinary bladder back through the ureter toward the kidney.
Where is the ureter located?
In each kidney, the ureter begins at the renal pelvis, at the level of the 2nd lumbar vertebra, and lies for 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 lesser pelvis, it is called the pars pelvetica of the ureter.
In their course, the ureters undercut and cross several blood vessels and are adjacent to the abdominal aorta on the left and the inferior vena cava on the right.
The ureters eventually approach the urinary bladder from the back above and pass through the wall at an oblique angle.
What problems can the ureter cause?
If problems occur in the ureter, urine transport is disrupted or urine flows back toward the kidneys.
Ureteral colic
Tumors
Various benign or malignant tumors can develop in the ureteral region.
Malformations
The ureters often show malformations. These can occur as ureteral dilatations (dilation), narrowing (stenosis) or occlusion (atresia). There are also protrusions of the ureteral wall (diverticula).
Reflux
If the ureter is dilated or the obstruction mechanism at the junction with the urinary bladder is disturbed, there may be a persistent backflow of urine into the ureter. In this way, bacteria can rise from the urinary bladder into the ureter and on to the kidney. The possible consequences are inflammation of the ureter and renal pelvis.
Injuries
A ureter can rupture in the event of severe injuries to the trunk of the body caused by accidents or surgical procedures.
