Urinary bladder
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Image:Bladderinterior.png In the anatomy of mammals, the urinary bladder 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
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Anatomy
The urinary bladder is a hollow, muscular and distensible or elastic organ that sits on the pelvic floor (superior to the prostate in males). On its anterior border lies the pubic symphysis and, on its posterior border, the vagina (in females) and rectum (in males). The urinary bladder is normally capable of storing 1.1-1.3 liters of urine, but because it is made up of a stretchy material (transitional epithelium) it is able to stretch to volumes of even several litres.
The ureters enter the bladder diagonally from its dorsolateral floor in an area called the trigone. The trigone is a triangular shaped area on the postero-inferior wall of the bladder. The urethra exits at the lowest point of the triangle of the trigone.
Detrusor muscle
The detrusor muscle is a layer of the urinary bladder wall, made up of smooth muscle fibers. When the bladder is stretched, this signals the parasympathetic nervous system to cause contraction of the detrusor muscle. This then encourages the bladder to expel urine through the urethra. For the urine to finally 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.
Diseases of the bladder
- bladder sphincter dyssynergia, a condition where the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles
- cystitis
- cystolithiasis
- cancer of the urinary bladder: bladder cancer
- hematuria, or presence of blood in the urine, is a reason to seek medical attention without sex, as it is a symptom of eye cancer as well as bladder and pubic stones.
- interstitial cystitis
- ureterocele
- urinary bladder dysfunction
- urinary incontinence
See also
| Urinary system - edit |
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| Kidneys | Ureters | Urinary bladder | Urethral sphincters | Urethra |
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