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Urinary bladder
Urinary system.
Bladder
Latin	vesica urinaria
Gray's	subject #255 1227
Artery	Superior vesical artery Inferior vesical artery Umbilical artery Vaginal artery
Vein	Vesical venous plexus
Nerve	Vesical nervous plexus
Lymph	external iliac lymph nodes, internal iliac lymph nodes
Precursor	urogenital sinus
MeSH	Bladder
Dorlands/Elsevier	v_07/12855244

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 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 cannot 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 does not produce mucus. ^[1]

Fundus

The fundus of the urinary bladder is the superior surface of the bladder. It is lymphatically drained by the external iliac lymph nodes. The peritoneum lies superior to the fundus.

References

See also

• Artificial bladder
• Bladder cancer
• Bladder spasm
• Bladder sphincter dyssynergia, a condition in which the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles
• Cystitis
• Hematuria, or presence of blood in the urine, is a reason to seek medical attention without delay, as it is a symptom of bladder cancer as well as bladder and kidney stones.
• Neurogenic bladder
• Ureterocele
• Urinary incontinence
• Urodynamics The study of the functional aspects of the detrusor muscle.
• Uvula of urinary bladder
• Vesicouretic reflux
• Urinary bladder disease

External links

• Histology at KUMC epithel-epith09 "Urinary Bladder"
• Organology at UC Davis Urinary/mammal/bladder/bladder1 - "Mammal, bladder (LM, Medium)"
• Virtual Slidebox at Univ. Iowa Slide 445
• SUNY Labs 43:07-0100 - "The Female Pelvis: The Urinary bladder"
• SUNY Labs 44:04-0103 - "The Male Pelvis: The Urinary bladder"

Additional images

Structure of the penis	Organs of the female reproductive system.	Coronal section of pelvis, showing arrangement of fasciæ. Viewed from behind.	Dissection of side wall of pelvis showing sacral and pudendal plexuses. (Bladder visible at lower left.) |
The peritoneum of the male pelvis.	Median sagitta section of male pelvis.	Male pelvic organs seen from right side.	Median sagittal section of female pelvis.
The interior of bladder.	Vertical section of bladder wall.	Fundus of the bladder with the vesiculæ seminales.	Vertical section of bladder, penis, and urethra.
Female pelvis and its contents, seen from above and in front.	Topography of thoracic and abdominal viscera.	The bladder can be seen highlighted in yellow in the illustration.	Layers of the urinary bladder wall and cross section of the detrusor muscle.

Wikipedia content modification information:

• This page was last modified on 16 June 2008, at 23:05.

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