Urinary bladder

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

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 can hold approximately 17 to 18 ounces (500 to 530 ml) of urine, however the desire to micturate is usually experienced when it contains about 150 to 200 ml.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.

The wall of the urinary bladder consists of three layers: 1) Mucosa, in this instance 'transitional epithelium' & lamina propria. 2) Detrusor Muscle that consists of an inner and outer longitudinal layer and a middle circular layer of smooth muscle. Finally, 3) a Fibrous Adventitia and the visceral peritoneum lie on superior surface.

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 delay, as it is a symptom of bladder cancer as well as bladder and kidney stones.
* Interstitial cystitis
* Ureterocele
* Urinary bladder dysfunction
* Urinary incontinence
* Urinary bladder rupture
* Vesicouretic Reflux

See also

* Artificial bladder