The ureter is a thin duct connecting the kidney and the bladder through which urine is removed from the kidney into the bladder. The structure and functions of the ureters ensure the normal functioning of the urinary system. Each kidney has its own ureter, which leaves the renal pelvis and enters the bladder. The length of each ureter is about 30 cm, the diameter ranges from 4 to 7 mm. The size of the ureter is of great importance in urolithiasis. Stones larger than 4 mm cannot exit freely with the flow of urine into the bladder and lead to the development of renal colic.
Ureter: structure of the abdominal and pelvic part
From the renal pelvis, the ureter goes down and into the middle and small pelvis, where it enters the bladder, perforating its wall in an oblique direction. In each ureter, the abdominal and pelvic parts are distinguished. The abdominal ureter is located in front of the large lumbar muscle. In front of the right ureter is the descending part of the duodenum, vessels and the base of the mesentery of the small intestine. In front of the left is the duodeno-jejunal bend, the vascular bundle and the base of the mesentery of the sigmoid colon.
In the pelvic part, the ureters pass in front of the iliac arteries and veins. The diameter of the ureter in this part is narrowed. In men, it passes in front of the vas deferens and below the upper pole of the seminal vesicle flows into the bladder. In the pelvic part, the ureters in women are surrounded by other organs: the ureter passes along the edge of the ovary and uterine neck, enters the bladder on the side of the vagina.
Intraventricular is the part of the ureter located inside the wall of the bladder.
Ureter: wall structure
The wall of the ureter, as well as the renal pelvis with cups, consists of three membranes: the outer one is made of connective tissue, the inner one is internally covered with transitional epithelium with mucous glands and the middle one consists of two layers of musculature - longitudinal and circular. The muscles of the ureters are not connected with the muscle layer of the bladder and prevents the return of urine from the bladder to the ureter.
At the place where the ureter enters the bladder, a layer of longitudinal muscles is located in its wall, which is closely connected with the muscle layer of the bladder. This layer actively prevents the backflow of urine into the ureter. The presence of this layer limits the spread of infection from the bladder to the ureter and further to the kidneys.
Ureter: lumen structure
The clearance of the ureter has several constrictions:
- the first narrowing is in the area of transition of the pelvis into the ureter;
- the second is located on the border between the abdominal and pelvic part;
- the third narrowing can be in any part of the pelvic part;
- the fourth narrowing is located near the wall of the bladder.
The presence of natural narrowing of the ureters is of great clinical importance. Stones emerging from the renal pelvis and moving with the flow of urine in the direction of the bladder get stuck in these areas.
In the course of the ureter, in addition to anatomical constrictions, there are physiological constrictions that appear and disappear during peristalsis.
Ureter: structure of blood supply and innervation
The upper part of the ureter receives blood from branches extending from the renal and testicular or ovarian arterial vessels. The middle part is supplied with blood from the ureteric branches extending from the abdominal aorta and iliac arteries. The lower part is from the bladder and middle rectal artery. The outflow of blood occurs in the internal iliac and lumbar veins.
The ureter is innervated from the following several autonomic nerve plexuses. Branches of the vagus nerve and pelvic internal nerves provide parasympathetic innervation.