Synonyms
Medical: Vesica urinaria bladder, urinary cystitis, cystitis, cystitis
The bladder is located in the pelvis. At the upper end, also called the apex vesicae, and at the back it is located in the immediate vicinity of the abdominal cavity with the intestines, from which it is separated only by the thin peritoneum. In women, the bladder is followed by the uterus at the back of the pelvis, and in men by the rectum.
The bladder can be divided into the apex vesicae, the corpus vesicae, the fundus vesicae and the neck of the bladder (CollumCervix vesicae). The two ureters, which are the connection between the kidney and the bladder, end in the bladder body. The neck of the bladder represents the transition to the urethra, which transports the urine outwards and forms the exit of the bladder. Cross-section through the bladder and underlying prostate:
- Bladder
- Urethra
- Prostate
- Seed mound with the two openings of the spray channels
- Prostate excretory ducts
Tasks of the bladder
The urinary bladder is a hollow muscular organ located in the pelvic region and can hold between 500 and 1000 ml of fluid, depending on body size. In the unfilled state it is strongly compressed by the surrounding abdominal organs. Its main task is to hold and store urine, the so-called continence, and to transport the urine to the outside in a regulated manner.
Once its storage capacity of 500 – 1000 ml has been reached, urine can be released in a controlled manner (micturition). Due to its structure, urine cannot usually rise against the direction of flow in the direction of the kidneys. This protects the kidneys from ascending pathogens, which could otherwise rise in the course of a bladder infection and cause a renal pelvic inflammation.
This is ensured by muscular occlusive apparatuses located at the point where the ureters join the bladder. The bladder stores the urine produced by the kidneys and delivered via the ureter. One ureter opens from each side in the lower part of the bladder.
Since the ureters run diagonally through the wall, they are compressed by the muscles of the wall, so that a backflow of urine (reflux) is prevented if nothing flows from the kidney from above. When the bladder has reached a certain filling level, the muscles in the bladder wall contract and the contents are transported outwards via the urethra. To ensure that the bladder is tight during storage, there are various closing mechanisms.
One is the inner closure (sphincter), which is located directly at the bladder outlet and is formed by muscle loops of the pelvic floor running in opposite directions. This closure opens with increasing pressure in the bladder and cannot be influenced arbitrarily. On the other hand, there is an external closure in the middle part of the urethra, which can be tensed arbitrarily.
From a filling of about 200 ml, the urge to urinate occurs, which becomes very strong from 400 ml. The bladder can hold a total of 600 – 1000 ml. Since the size of the bladder varies greatly with the filling, the mucous membrane lining the inside (tunica mucosae) is wrinkled when empty.
These wrinkles disappear as the filling increases. In addition, the spherical cells of the mucosa (cover cells) can flatten out with filling and create even more space for expansion and thus urine. The cover cells also prevent the aggressive urine from damaging the bladder.
The bladder is emptied by a reflex triggered by the brain, which receives information about the filling state of the bladder from nerve fibers in the spinal cord. Normally, this reflex is suppressed until a favourable opportunity for emptying arises, i.e. emptying can be controlled arbitrarily. Without filling, the mucosa lies in folds, but as the bladder fills up, the surface becomes smooth.
