What is the urinary bladder?
The urinary bladder, colloquially called “bladder” for short, is an expandable hollow organ in which the body temporarily stores urine. It is emptied voluntarily from time to time (micturition). The maximum capacity of the human bladder is 900 to 1,500 milliliters. As it fills, the bladder enlarges, which is possible thanks to its wrinkled skin. The shape changes from spherical to pear-shaped.
Read more about the anatomy of the bladder below:
The human bladder is divided into three sections: At the top is the apex of the bladder, in the middle is the body of the bladder (corpus), and at the bottom is the base of the bladder (fundus). When filled, the apex of the bladder can be felt through the abdominal wall.
The two ureters open into the upper part of the bladder. Their oblique course and slit-like orifice create a valve-like obstruction that prevents urine from flowing back toward the kidneys.
Bladder sphincters
In the area of the urethral orifice, there are two sphincters. They prevent urine from leaking out of the bladder. If the bladder is emptied voluntarily or involuntarily (for example, in the case of incontinence), the smooth muscles of the bladder wall contract and the sphincters open – the urine can flow out through the urethra.
These processes are controlled by nerve impulses from the sacral plexus.
Muscle wall and mucosa
What is the function of the urinary bladder?
The urinary bladder serves as a temporary storage facility for urine. This is where the waste product is collected and stored to be disposed of when the opportunity arises. Since the kidneys produce urine continuously, without the urinary bladder urine would be excreted all the time.
“Bladder full” – this signal reaches the brain much earlier, however, thanks to sensors in the bladder wall that are stretched as the bladder contents increase. In adults, the urge to urinate usually occurs when the bladder fills up to 200 to 500 milliliters. From this bladder content, the urge to empty the bladder is felt.
Where is the urinary bladder located?
The urinary bladder is located in the small pelvis, behind the pubic bones and the pubic symphysis. When empty, the bowl-shaped urinary bladder does not cross the upper edge of the pubic bones and therefore cannot be palpated through the abdominal wall. One wonders: where exactly is the bladder located? In contrast, it is easy to determine the position as the urine fills. Here, pressure on the bladder with the hand increases the urge to urinate and thus makes localization very easy.
In women, the urinary bladder is adjacent to the uterus at the back of the pelvis; in men, the rectum is adjacent at the back. In both sexes, the urinary bladder rests on the pelvic floor and the urethra passes through the pelvic floor. The two sphincters of the urinary bladder are also found in this area. The urinary bladder is covered by peritoneum in the upper and posterior regions, and thus lies outside the abdominal cavity.
There are a variety of acquired and congenital diseases of the urinary bladder. Women and men are equally affected. However, women suffer more frequently from inflammation of the bladder (cystitis). This is because their shorter urethra makes it easier for germs to enter the bladder and infect it.
In addition, there is also the so-called irritable bladder. This manifests itself in a constant, often sudden urge to urinate, although only small amounts of urine are ever released from the bladder. Sometimes the explanation can be found in neurological diseases, bladder stones, bladder tumors or infections. Very often, however, the cause remains unexplained.
Tumors can also form on the urinary bladder (bladder cancer), this happens mainly in older age. Other possible diseases are urinary bladder fistulas or sac-like protrusions on the bladder wall (urinary bladder diverticula).
If the filled bladder cannot be emptied naturally, this is called urinary retention. This condition is a medical emergency and can lead to kidney damage.
