Everything about Detrusor totally explained
In
anatomy, the
urinary bladder is a hollow,
muscular, and distensible (or elastic) organ that sits on the
pelvic floor in
mammals. It is the organ that collects
urine excreted by the
kidneys prior to disposal by
urination. Urine enters the bladder via the
ureters and exits via the
urethra.
In males, the bladder is superior to the
prostate, and separated from the
rectum by the
rectovesical excavation.
In females, the bladder is separated from the
rectum by the
rectouterine excavation, and it's separated from the
uterus by the
vesicouterine excavation.
Detrusor muscle
The detrusor muscle is a layer of the urinary bladder wall made of
smooth muscle fibers arranged in spiral, longitudinal, and circular
bundles. When the bladder is stretched, this signals the
parasympathetic nervous system to contract the
detrusor muscle. This encourages the bladder to expel
urine through the
urethra.
For the urine to exit the bladder, both the
autonomically controlled internal
sphincter and the
voluntarily controlled external sphincter must be opened. Problems with these muscles can lead to
incontinence. If the amount of urine reaches 100% of the urinary bladder volume, the voluntary sphincter becomes involuntary and the urine will be ejected instantly. The body can't afford having the urinary bladder burst.
The urinary bladder usually holds 400–620 mL of urine, but it can hold twice this without rupturing if, for example, the outflow is obstructed.
The desire to
urinate usually starts when the bladder reaches around 75% of its working volume. If the subject is distracted the desire can fade and return with more urgency as the bladder continues to fill.
Since the urinary bladder has a
transitional epithelium, compared to the intestine mucosa, the urinary bladder doesn't produce mucus.
Fundus
The fundus of the urinary bladder is the bottom of the bladder. It is
lymphatically drained by the
external iliac lymph nodes.
Clinical Significance
- Cystitis cystica is a chronic cystitis glandularis accompanied by the formation of cysts. This disease can cause chronic urinary tract infections.
- Interstitial cystitis is a bladder disease of unknown etiology characterized by a bladder wall infiltrated by inflammatory cells resulting in ulcerated mucosa and scarring, spasm of the detrusor muscle, hematuria, urgency, increased frequency, and pain on urination.
- The bladder may rupture if overfilled and not emptied. This can occur in the case of binge drinkers who have consumed large quantities, but are not conscious due to stupor of the need to urinate. This condition is very rare in women, but does occur. Symptoms include localized pain and uraemia (poisoning due to reabsorbed waste).
Further Information
Get more info on 'Detrusor'.
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