How The Bladder Works

Date: 08/11/21

The bladder is basically a large muscly sack used to collect and store urine until it is convenient for us to expel it by visiting the toilet. It is fed by two tubes from the kidneys, around 25-30cm long, called ureters, and it is drained by a tube leading to the outside of the body, called the urethra. This is around 4cm long in women and up to 20cm long in men. The whole system is controlled by both voluntary and involuntary nerve signals that send messages to and from the brain.

In this article we will take a detailed look at the structure of the bladder and how it operates, and we will show how incontinence can occur when certain elements of the system fail.

The structure of the bladder

The bladder is a muscular sack comprising four distinct layers:

  • Epithelium – the inner lining of the bladder
  • Lamina propria – a matrix made of connective tissue, muscle, fat cells, nerve endings and blood vessels
  • Muscularis propria – a layer of muscle fibres known as the detrusor muscle
  • Perivesical tissue – an outer lining of fat and fibres that keeps the bladder separate from nearby organs.

The bladder is around two inches long and pyramid shaped when empty, and it can stretch to around six inches and spherical when full. It can hold between 400ml and 600ml of urine for up to five or six hours if necessary.

The two ureters carrying urine from the kidneys enter near the base of the bladder, at the edge of a funnel shaped muscular structure called the trigone. Small amounts of urine arrive from the kidneys several times every minute as the muscles of the ureter contract. The amount of urine depends on fluid intake from food and drinks and fluid loss through sweating and breathing. At the apex of the trigone is the urethra, where urine exits the bladder.

Bladder sphincters

The flow of urine out of the bladder is controlled by two circular muscle groups called sphincters:

  • Internal sphincter – this sits at the base of the bladder and automatically keeps the urethra closed
  • External sphincter – this sits a short way along the urethra and we have conscious control about when it opens and closes

The bladder is supported by a sheet of muscles in the lower abdomen called the pelvic floor. The pelvic floor muscles also provide support to the sphincters, helping them to  stay closed.

How the bladder works

As the bladder starts to fill, the muscular walls expand to increase its volume. Once this reaches between a third and half full, around 200ml, the nerves trigger a signal to the brain, called the micturition reflex, that tells you that you will need to urinate soon. The bladder then continues to fill until you choose to empty it.

When you decide to empty your bladder, your brain sends signals to the detrusor muscle to contract, pushing the urine out into the urethra. It also sends signals to the sphincter muscles and to the pelvic floor, telling them to relax and allow the urine to pass.

If you are not able to urinate at that time, the bladder volume will continue to increase until the contractions of the detrusor muscles force open the internal sphincter, leaving the external sphincter as your last line of defence. Although this can feel very uncomfortable, like you are literally bursting for a wee, you will still be in control of the external sphincter for a significant amount of time.

Bladder problems and urinary incontinence

For complete continence, you need all parts of the bladder system to work correctly. If they don’t, then incontinence will occur, requiring support from Tena incontinence pants or child incontinence pants. The nature of the problem will dictate the type of incontinence:

  • Urge incontinence – this occurs when the bladder signals become confused leading you to think it is fuller than it is and giving you the urge to urinate sooner, and more often, than you actually need to. Instead of stretching to accommodate more fluid, the bladder starts contracting creating an urgent need to urinate.
  • Stress incontinence – this occurs when the sphincters or the pelvic floor are not able to fully close the urethra when under pressure from coughing, laughing or sudden movements, leading to uncontrolled leaks.
  • Combination incontinence – this occurs when the nerves are damaged or non-functional, leading to a mixture of urge and stress incontinence symptoms.

Complete, discreet support

Whatever the issues with your bladder and bladder control, Incodirect have a wide range of incontinence products available, including leading brands like Tena incontinence pants, that can help you deal with the problem and continue to live a full and active life. Talk to our friendly team today for free, expert advice and understanding. To find out more about Incodirect’s incontinence products such as Tena incontinence pants visit our shop:

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