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The lower urinary system is made up of the bladder, with the bladder muscles and the urethra with its sphincter muscle.
Bladder
Your bladder’s job is to store and empty urine. The muscles in your pelvis are important for your ability to hold the urine inside. The walls of the bladder are made up of lots of thin muscle layers, these are relaxed until you flex and contract them when you are going to the toilet.
In the walls of your bladder you can find receptors that register the expansion of your bladder as it fills up, these send messages to your brain that it is filling up. You will then feel the first urge to go to the toilet. When the bladder contains about 400ml you will feel a strong urge to go to the toilet.
Urethra
A woman’s urethra is about 3-5cm long and a mans is much longer, about 20-27cm long. The urethral opening is called the meatus.
Urethra’s Sphincter Muscle
Below the bladder where the urethra begins you find a sphincter muscle. This is very important for your ability to keep urine inside your body until you want to let it out. It is the gateway to your bladder.
The purpose of your sphincter muscle is to squeeze the urethra shut as the bladder fills with urine and to relax and open when you want to empty your bladder. This requires good communication between the bladder and the urethra.
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