urinary bladder


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urinary bladder

a distensible membranous sac in which the urine excreted from the kidneys is stored

Urinary Bladder

 

the organ in which urine accumulates before being excreted from the body in certain invertebrates, in most vertebrates, and in man.

The urinary bladder takes several forms in invertebrates: rotifers have an unpaired bladder, oligochaetes and hirudineans (leeches) have multiple bladders, and higher crustaceans have paired bladders. In the vertebrates, the urinary bladder is usually unpaired. In female elasmobranchs, paired urinary bladders, or urinary sinuses, occur as widenings of the ureters; these sinuses merge in the posterior end of the body into an unpaired urinary sinus that opens into the cloaca. In most teleosts, the urinary bladder occurs as a widening of the ureters that merge into a terminal unpaired duct; this duct can have its own external orifice, or it can share an orifice with the terminal sections of the gonaducts in males of certain species.

In most terrestrial vertebrates, the urinary bladder is formed from the embryonic membrane called the allantois; amphibians are the only class in which the bladder arises from a ventral diverticulum of the cloaca. In amphibians, reptiles, and monotremes, the urinary bladder opens into the cloaca opposite the cloacal openings of the ureters. In metatherians (marsupials) and eutherians (placental mammals), the ureters empty directly into the urinary bladder, which in turn is usually connected to the exterior by the urethra. The ureters empty into the urogenital sinus only in the females of certain animals. Birds have no urinary bladder, and crocodilians and Serpentes (snakes) are the only reptiles in which this structure is rudimentary.

In man, the urinary bladder is a hollow, muscular organ situated in the lesser pelvis. Its average capacity is 500 cc, but when distended, it can hold much more urine. The bladder’s walls are lined with mucosa. Urine passes through the ureters from the kidneys and is deposited into the urinary bladder every 10–20 seconds. The neck of the urinary bladder opens into the first section of the urethra; ring-shaped muscles are located in the neck and form two sphincters that surround and close the urethra. Contraction of the sphincters prevents the urine from flowing out of the bladder. When the bladder is full, neural elements in the bladder wall elicit reflex contractions of the bladder muscles, as well as relaxation of the sphincteral muscles; these simultaneous processes result in the outflow of urine through the urethra.

In males, the posterior wall of the bladder is adjacent to the rectum; the neck of the bladder and the first section of the urethra are surrounded by the prostate gland. Diseases of the prostate can interfere with and even prevent urination. In females, the posterior wall of the bladder is adjacent to the uterine cervix and to the vagina.

The mucous membrane of the bladder is extremely susceptible to infection. The short length of the female urethra facilitates the spread of infections from the genitalia to the bladder. In males, the bladder can become infected because of an impairment in the excretory function, as occurs in diseases of the prostate.

urinary bladder

[′yu̇r·ə‚ner·ē ′blad·ər]
(anatomy)
A hollow organ which serves as a reservoir for urine.
References in periodicals archive ?
12] reported a case of a 70-year-old woman who had multiple recurrences of nephrogenic metaplasia of the urinary bladder with the subsequent development of clear cell adenocarcinoma.
This involves introducing a small needle directly into the urinary bladder.
The total number of urinary bladder cancers was 316 cases, accounting for 65% of the total urinary bladder biopsies during the period of study.
Positive contrast radiography of urinary bladder was performed using contrast agent (diatrizoate meglumine and diatrizoate sodium-76%) on days 30, 60 and 90 post-implantation to evaluate the healing status.
A retrospective study was done in seven provinces of Canada23 comprising of 887 cases and 2847 controls (matching age and gender) suffering from urinary bladder cancer from 1994 to 1997.
A supernumerary cloacal septum that indents the epithelial of the urinary bladder.
The urinary bladder is a flexible, muscular bag that collects urine from the kidneys via the ureters for storage and eventual elimination.
Most common site of presentation is lateral walls of urinary bladder.
Ultrasonography showed a well circumscribed polypoidal lesion projecting into the urinary bladder on the left side causing mild hydronephrosis of the left kidney.
Keywords: matrix metalloproteinases, urinary tract tumors, urinary bladder carcinoma
The VCUG identifies a large urinary bladder capacity, 500 milliliters (mL), with bladder irregularities consistent with long-standing bladder outlet obstruction or neurogenic bladder.
Objective: The objective of this study was to determine the efficacy of hypofractionated external-beam radiotherapy for management of macroscopic hematuria in patients with advanced urinary bladder cancer.

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