Urinary bladder
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In anatomy, the urinary bladder (roughly translated from vesicle) is a hollow [1] muscular, and distensible (or elastic) organ that sits on the pelvic floor. 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.
Embryologically, the Bladder is derived from the Urogenital sinus and, it is initially continuous with the allantois.
In males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the prostate, and separated from the rectum by the rectovesical excavation.
In females, the bladder sits inferior to the uterus and anterior to the vagina. It is separated from the uterus by the vesicouterine excavation.
In infants and young children, the urinary bladder is in the abdomen even when empty.[2]
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[edit] 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, although it is possible to "hold yourself" in order to prevent urination.
The urinary bladder usually holds 400–620 mL of urine[citation needed], but it can hold twice this without rupturing[citation needed] if, for example, the outflow is obstructed.
The desire to urinate usually starts when the bladder reaches around 25%[3] 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.[4]
[edit] Fundus
The fundus of the urinary bladder is the base of the bladder, formed by the posterior wall. It is lymphatically drained by the external iliac lymph nodes. The peritoneum lies superior to the fundus.
[edit] Disorders
Disorders of or related to the bladder include:
- Overactive bladder, a condition which affects a large number of people.
- Bladder cancer
- Bladder infection
- 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
- Bladder stones
- Cystitis
- Interstitial 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.
- Urinary incontinence
- Bladder exstrophy
[edit] Uses
Besides its normal use to the possessor, animal bladders (usually pig bladders) have been used to make balls (such as footballs) and even a musical instrument, the bumbass.
[edit] See also
- Artificial bladder
- Bladder augmentation
- Neurogenic bladder
- Ureterocele
- Urodynamics The study of the functional aspects of the detrusor muscle.
- Uvula of urinary bladder
- Vesicouretic reflux
- Urinary bladder disease
- Interstitial Cystitis
[edit] References
- ^ Howard A. Werman, MD and Keith J. Karren, PhD.
- ^ Moore, Keith L.; Dalley, Arthur F, Clinically Oriented Anatomy, 5th Edition, 2006 Lippincott Williams & Wilkins
- ^ [1]
- ^ T . Chin , C . Liu , H . Tsai , C . Wei. Vaginal reconstruction using urinary bladder flap in a patient with cloacal malformation
[edit] 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"
[edit] 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. |
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