The Urinary Bladder

The Urinary Bladder is a hollow, elastic, muscular organ that sits on the pelvic floor. The Urinary Bladder collects urine excreted from the kidneys via the Ureters and when the urine leaves the bladder it does so via the urethra. Normally the Urinary Bladder can hold about 400-600mL of urine but in special cases the bladder may be able to hold up to the double amount of urine! The urge to urinate normally starts when the bladder is about 75% full and can then fade only to come back even more urgent as the urinary bladder is filled up.

The Urinary Bladder Wall

The wall of the Urinary Bladder consists of three layers:

The Detrosor Muscle of the Urinary Bladder

The Detrusor Muscle is a layer of the Urinary Bladder wall which is itself made up by three layers. The Detrusor Muscle is smooth muscle fibers arranged in spiral and circuar bundles. When the urinary bladder is stretched the parasympathetic nervous system is signaled to contract the detrusor muscle and the urine is squeezed out through the urethra canal. For this to work both the autonomically controlled sphincter muscle and the voluntarily controlled sphincter muscle must be relaxed.