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The bladder wall consists of four layers: the urothelium or transitional epithelium that lines the internal surface, a layer of connective tissue consisting of blood vessels and nerves, a thick muscle layer, and an outer layer of fatty tissue that separates the bladder from other organs.
A hollow muscular organ situated at the base of the pelvis.
The urinary bladder is an extraperitoneal muscular urine reservoir that lies behind the pubic symphysis in the pelvis.
Most of it develops from the urogenital sinus but the sensitive trigone region develops from the mesoderm of the mesonephric duct.
A hollow muscular organ that collects and stores urine from the kidneys before disposal by urination.
In the human the bladder is a hollow muscular, and distensible organ, that sits on the pelvic floor.
Urine enters the bladder via the ureters and exits via the urethra.
The typical human bladder will hold between 300 and 500 mL (10.14 and 16.91 fl oz) before the urge to empty occurs.
Urine collects in the bladder, fed from the two ureters that connect the bladder with the kidneys.
Urine leaves the bladder via the urethra, a single muscular tube which ends in an opening, the urinary meatus, where it exits the body.
The bladder is divided intoxicated:
a broad fundus
a body
an apex
a neck
The apex is directed forward toward the upper part of the pubic symphysis.
From the Apex and the median umbilical ligament continues upward on the back of the anterior abdominal wall to the umbilicus.
The neck of the bladder is the area at the base of the trigone that surrounds the internal urethral orifice that leads to the urethra.
In males the neck of the urinary bladder is adjacent to the prostate gland.
The three openings, two ureteric orifices, and the internal urethral orifice mark the triangular area called the trigone of the bladder.
These openings have mucosal flaps in front of them that act as valves in preventing the backflow of urine into the ureters.
Between the two ureteric openings is a raised area of tissue called the interureteric crest, making the upper boundary of the trigone.
The trigone is a smooth-muscle area that forms the floor of the bladder above the urethra.
The trigone is an area of smooth tissue for the easy flow of urine into and from this part of the bladder.
The trigone is an area of smooth tissue in contrast to irregular surface formed by the rugae.
In men, the prostate gland lies outside the opening for the urethra.
The middle lobe of the prostate causes an elevation in the mucous membrane behind the internal urethral orifice called the uvula of urinary bladder.
The uvula can enlarge when the prostate becomes enlarged.
The bladder is situated below the peritoneal cavity near the pelvic floor and behind the pubic symphysis.
In males, the base of the bladder lies between the rectum and the pubic symphysis.
In men the bladder is superior to the prostate, and separated from the rectum by the recto-vesical pouch.
In men, it lies in front of the rectum, separated by the recto-vesical pouch, and is supported by fibers of the levator ani and of the prostate gland.
In females, the bladder sits inferior to the uterus and anterior to the vagina.
In women the bladder’s maximum capacity is lower than in males.
In women the bladder t is separated from the uterus by the vesico-uterine pouch.
In infants and young children the urinary bladder is in the abdomen.
In women, the bladder lies in front of the uterus, separated by the vesico-uterine pouch, and is supported by the levator ani and the upper part of the vagina.
The wall of the urinary bladder is normally 3–5 mm thick.
When the bladder is well distended, the wall is normally less than 3 mm.
The inner walls have a series of ridges, thick mucosal folds known as rugae that allow for the expansion of the bladder.
The outside of the bladder is protected by a serous membrane.
The bladder wall itself is smooth muscle.
The inner side of the bladder is lined with a mucosal membrane consisting of a surface glycocalyx that protects the cells beneath it from urine, the urothelium , a basement membrane, and the lamina propria.
The mucosal lining also offers a urothelial barrier against infections.
The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle fibers arranged in spiral, longitudinal, and circular bundles.
Stretch receptors in the bladder signal the parasympathetic nervous system to stimulate the muscarinic receptors in the detrusor to contract the muscle when the bladder is extends encouraging it to expel urine through the urethra.
The main muscarinic receptor activated is the M3 receptor.
The main relaxant pathway in the detrusor muscle is via the adenylyl cyclase cAMP pathway, activated by β2 adrenergic receptors.
The detrusor muscle is able to change its length, and can also contract for a long time when voiding, and it stays relaxed while the bladder is filling.
The bladder is supplied by the vesical arteries and drained by the vesical veins.
The superior vesical artery supplies blood to the upper part of the bladder.
The lower part of the bladder is supplied by the inferior vesical artery in males and by the vaginal artery in females, both are branches of the internal iliac arteries.
Venous drainage begins on the lateral and posterior surfaces of the bladder, the small vessels which coalesce and pass into the internal iliac veins.
The lymph drainage begins in networks throughout the mucosal, muscular and serosal layers in three sets of vessels: one set near the trigone draining the bottom of the bladder; one set draining the top of the bladder; and another set draining the outer undersurface of the bladder.
The majority of lymphatics drain into the external iliac lymph nodes.
The bladder motor innervation from both sympathetic and parasympathetic fibers.
Most of the sympathetic fibers arise from the superior and inferior hypogastric plexuses and nerves.
The parasympathetic fibers come from the pelvic splanchnic nerves.
Bladder sensation neurologically is transmitted to the central nervous system (CNS) via general visceral afferent fibers.
General visceral fibers on the superior surface of the bladder follow the sympathetic efferent nerves back to the CNS.
General visceral fibers on the inferior portion of the bladder follow the course of the parasympathetic efferents.
Both the autonomically controlled internal sphincter, in the male, and the voluntarily controlled external sphincter must be opened before urine can exit the bladder.
When an imbalance of these sphincter muscles occurs it can lead to incontinence.
Urinary bladder abnormalities include:
Calcifiications on bladder wall.
Bladder diverticulum
Bacteriuria
Interstitial cystitis
Incontinence and retention
Bladder exstrophy.
Bladder sphincter dyssynergia.
Paruresis
Trigonitis
Urinary retention
Bladder cancer
Urine collects in the bladder, fed from the two ureters that connect the bladder with the kidneys.
Urine leaves the bladder via the urethra.
The urethra is a single muscular tube which ends in the urinary meatus, where it exits the body.
The bladder is divided anatomically:
a broad fundus
a body
an apex
a neck
The neck of the bladder is the area at the base of the trigone that surrounds the internal urethral orifice that leads to the urethra.
In males the neck of the urinary bladder is adjacent to the prostate gland.
Two ureteric orifices, and the internal urethral orifice mark the triangular area called the trigone of the bladder.
The three openings have mucosal flaps in front of them that act as valves in preventing the backflow of urine.
These flaps prevent vesicoureteral reflux.
The trigone is a smooth-muscle area that forms the floor of the bladder above the urethra.
The trigone is an area of smooth tissue for the easy flow of urine into and from this part of the bladder.
In men, the prostate gland lies outside the opening for the urethra.
The middle lobe of the prostate causes an elevation in the mucous membrane behind the internal urethral orifice called the uvula of urinary bladder.
The uvula can enlarge when the prostate becomes enlarged.
The bladder is situated below the peritoneal cavity near the pelvic floor and behind the pubic symphysis.
In males, the bladder lies in front of the rectum, separated by the recto-vesical pouch, and is supported by fibers of the levator ani and of the prostate gland.
In women, the bladder lies in front of the uterus, separated by the vesico-uterine pouch, and is supported by the elevator ani and the upper part of the vagina.
The wall of the urinary bladder is normally 3–5 mm thick.
When well distended, the urinary bladder wall is normally less than 3 mm.
The inner walls have thick mucosal folds known as rugae that allow for the expansion of the bladder.
The outside of the bladder is protected by a serous membrane.
The bladder wall is made up of smooth muscle.
The inner side of the bladder is lined with a mucosal membrane consisting of a surface glycocalyx, urothelium,a basement membrane, and the lamina propria.
The mucosal lining also offers a barrier against the passing of infections.
The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle arranged in spiral, longitudinal, and circular bundles.
Stretch receptors in the bladder signal the parasympathetic nervous system to stimulate the muscarinic receptors in the detrusor to contract the muscle when the bladder is extended.
Muscarinic receptors in the detrusor to contraction encourages the bladder to expel urine through the urethra.
The main receptor activated is the M3 receptor.
M2 receptors are also involved and whilst outnumbering the M3 receptors they are not so responsive.
The main bladder relaxant pathway is via the adenylyl cyclase cAMP pathway, activated by β2 adrenergic receptors.
The detrusor muscle is able to change its length, and can also contract for a long time when voiding, and it stays relaxed while the bladder is filling.
The bladder is supplied by the vesical arteries and drained by the vesical veins.
The superior vesical artery supplies blood to the upper part of the bladder.
The lower part of the bladder is supplied by the inferior vesical artery in males and by the vaginal artery in females, both of which are branches of the internal iliac arteries.
Venous drainage begins in a network of small vessels on the lateral and posterior surfaces of the bladder, which coalesce and pass backwards along the lateral ligaments of the bladder into the internal iliac veins.
The lymph system draining the bladder begins in a series of networks throughout the mucosal, muscular and serosal layers, and then form three sets of vessels.
The majority of these vessels drain into the external iliac lymph nodes.
The bladder receives motor innervation from sympathetic fibers, most of which arise from the superior and inferior hypogastric plexuses and nerves, and from parasympathetic fibers, which come from the pelvic splanchnic nerves.
Sensation from the bladder is transmitted to the central nervous system by general visceral afferent fibers.
General visceral afferent fibers on the superior surface follow the course of the sympathetic efferent nerves back to the CNS.
General visceral afferent fibers on the inferior portion of the bladder follow the course of the parasympathetic efferents.
For the urine to exit the bladder, both the autonomically controlled internal sphincter, in the male, and the voluntarily controlled external sphincter must be opened.
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 recto-vesical pouch.
In females, the bladder sits inferior to the uterus and anterior to the vagina; thus its maximum capacity is lower than in males.
In women it is separated from the uterus by the vesico-uterine pouch.
In infants and young children the urinary bladder is in the abdomen.
Urine collects in the bladder before disposal by urination.
The urinary bladder usually holds 300-350 ml of urine.
As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure.
Urination is controlled by the pontine micturition center in the brainstem.
The presence of bacteria in the urine which can indicate a urinary tract infection.
Frequent urination can be due to excessive urine production, small bladder capacity, irritability or incomplete emptying.
Though both urinary frequency and volumes have been shown to have a circadian rhythm, meaning day and night cycles,
An underactive bladder is the condition where there is a difficulty in passing urine and is the main symptom of a neurogenic bladder.
Frequent urination at night may indicate the presence of bladder stones.
Disorders of or related to the bladder include:
Bladder exstrophy
Bladder sphincter dyssynergia
Paruresis
Trigonitis
Urinary retention
Disorders of bladder function may be dealt with surgically, by re-directing the flow of urine or by replacement with an artificial urinary bladder.