Urine, excreted by the kidneys, collects in the bladder because of drainage from two ureters, before disposal by urination (micturition). Urine leaves the bladder via the urethra, a single muscular tube ending in an opening called the urinary meatus, where it exits the body. Urination involves coordinated muscle changes involving a reflex based in the spine, with higher inputs from the brain. During urination, the destrusor muscle contracts, and the external urinary sphincter and muscles of the perineum relax, allowing urine to pass through the urethra and out of the body. The urge to pass urine stems from stretch receptors that activate when between 300 - 400 mL urine is held within the bladder.
Function
Urinary bladder
Urinary bladder | Function
Urine, excreted by the kidneys, collects in the bladder Urine, produced by the kidneys, travels along the ureters to the bladder. Excretion of urine, urge to release urine Urine, produced by the kidneys, travels along the ureters to the bladder
what tissue types form the wall of the ureter
user
urothelial cells
assistant
what is ureter?
user
The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder.
assistant
what is the size of this tube?
user
The ureters are between 1.5 - 6 mm in diameter, and surrounded by a layer of smooth muscle for 1 - 2 cm near their ends just before they enter the bladder.
assistant
can you name one function of this bladder?
user
In males the neck of the urinary bladder is next to the prostate gland. The bladder has three openings. The two ureters enter the bladder at ureteric orifices, and the urethra enters at the trigone of the bladder. These ureteric openings have mucosal flaps in front of them that act as valves in preventing the backflow of urine into the ureters, known as vesicoureteral reflux. Between the two ureteric openings is a raised area of tissue called the interureteric crest. This makes the upper boundary of the trigone. The trigone is an area of smooth muscle that forms the floor of the bladder above the urethra.
Urinary bladder | Structure
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. 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. This encourages the bladder to expel urine through the urethra. The main receptor activated is the M3 receptor, although M2 receptors are also involved and whilst outnumbering the M3 receptors they are not so responsive.
Urinary bladder | Function
During urination the muscle is contracted via parasympathetic branches from the pelvic splanchnic nerves to empty the bladder. At other times the muscle is kept relaxed via sympathetic branches from the inferior hypogastric plexus to allow the bladder to fill.
Detrusor muscle | Function
Urine, excreted by the kidneys, collects in the bladder because of drainage from two ureters, before disposal by urination (micturition). Urine leaves the bladder via the urethra, a single muscular tube ending in an opening called the urinary meatus, where it exits the body. Urination involves coordinated muscle changes involving a reflex based in the spine, with higher inputs from the brain. During urination, the destrusor muscle contracts, and the external urinary sphincter and muscles of the perineum relax, allowing urine to pass through the urethra and out of the body. The urge to pass urine stems from stretch receptors that activate when between 300 - 400 mL urine is held within the bladder.
Urinary bladder | Function
The urinary bladder, or simply bladder, is a hollow muscular organ in humans and other vertebrates that 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 (10.14 and ) before the urge to empty occurs, but can hold considerably more. The Latin phrase for "urinary bladder" is "vesica urinaria", and the term "vesical" or prefix "vesico -" appear in connection with associated structures such as vesical veins.
Urinary bladder | Introduction
It is an area of smooth tissue for the easy flow of urine into and from this part of the bladder - in contrast to the irregular surface formed by the rugae. The walls of the bladder have a series of ridges, thick mucosal folds known as rugae that allow for the expansion of the bladder. The detrusor muscle is the muscular layer of the wall made of smooth muscle fibers arranged in spiral, longitudinal, and circular bundles. The detrusor muscle is able to change its length. It can also contract for a long time whilst voiding, and it stays relaxed whilst the bladder is filling.
Urinary bladder | Structure
The ureters are tubular structures, approximately in adults, that pass from the pelvis of each kidney into the bladder. From the renal pelvis, they descend on top of the psoas major muscle to reach the brim of the pelvis. Here, they cross in front of the common iliac arteries. They then pass down along the sides of the pelvis, and finally curve forwards and enter the bladder from its left and right sides at the back of the bladder. The ureters are between 1.5 - 6 mm in diameter, and surrounded by a layer of smooth muscle for 1 - 2 cm near their ends just before they enter the bladder.
Ureter | Structure
At this time the ureters move from the mesonephric ducts to the trigone. 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. It is separated from the uterus by the vesico-uterine pouch. In infants and young children the urinary bladder is in the abdomen even when empty.
Urinary bladder | Development
The ureters enter the bladder from its back surface, traveling before opening into the bladder at an angle on its outer back surface at the slit-like "ureteric orifices". This location is also called the vesicoureteric junction. In the contracted bladder they are about apart and about the same distance from the internal urethral orifice; in the distended bladder these measurements may be increased to about . A number of structures pass by, above, and around the ureters on their path down from the kidneys to the bladder. In its upper part, the ureter travels on the psoas major muscle, and sits just behind the peritoneum.
Ureter | Structure
This is the primary muscle for maintaining continence of urine, a function shared with the external urethral sphincter which is under voluntary control. It prevents urine leakage as the muscle is tonically contracted via sympathetic fibers traveling through the inferior hypogastric plexus and vesical nervous plexus. Specifically, it is controlled by the hypogastric nerve, predominantly via the alpha-1 receptor. During urination, the preganglionic neurons of this sympathetic pathway are inhibited via signals arising in the pontine micturition center and traveling through the descending reticulospinal tracts, allowing the muscle to relax. During ejaculation, the muscle contracts to prevent reflux of semen into the urinary bladder, a phenomenon called retrograde ejaculation.
Internal urethral sphincter | Function
In humans, the bladder is a hollow muscular organ situated at the base of the pelvis. In gross anatomy, the bladder can be divided into a broad , a body, an apex, and a neck. The apex is directed forward toward the upper part of the pubic symphysis, and from there the median umbilical ligament continues upward on the back of the anterior abdominal wall to the umbilicus. The peritoneum is carried by it from the apex on to the abdominal wall to form the middle umbilical fold. 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.
Urinary bladder | Structure
The body stores urine — water and wastes removed by the kidneys — in the urinary bladder, a balloon-like organ. The bladder connects to the urethra, the tube through which urine leaves the body. Continence and micturition involve a balance between urethral closure and detrusor muscle activity (the muscle of the bladder). During urination, detrusor muscles in the wall of the bladder contract, forcing urine out of the bladder and into the urethra. At the same time, sphincter muscles surrounding the urethra relax, letting urine pass out of the body. The urethral sphincter is the muscular ring that closes the outlet of the urinary bladder preventing urine to pass outside the body.
Urinary incontinence | Adults
These layers are surrounded by three layers of muscle fibres arranged as an inner layer of fibres orientated longitudinally, a middle layer of circular fibres, and an outermost layer of longitudinal fibres; these form the destrusor muscle, which can be seen with the naked eye.
Urinary bladder | Microanatomy
The AUM is believed to be involved in strengthening the cells that line the bladder, and in enhancing the inner bladder membrane's ability to stretch, thus preventing these cells from rupturing during bladder distension. The use of alternate polyadenylation sites has been found for this gene.
UPK1B | Function
The internal urethral sphincter provides involuntary control of urination. The external urethral sphincter provides voluntary control of urination. Any damage to these muscles can lead to urinary incontinence.
Urethral sphincters | Function
The main organs involved in urination are the urinary bladder and the urethra. The smooth muscle of the bladder, known as the detrusor, is innervated by sympathetic nervous system fibers from the lumbar spinal cord and parasympathetic fibers from the sacral spinal cord. Fibers in the pelvic nerves constitute the main afferent limb of the voiding reflex; the parasympathetic fibers to the bladder that constitute the excitatory efferent limb also travel in these nerves. Part of the urethra is surrounded by the male or female external urethral sphincter, which is innervated by the somatic pudendal nerve originating in the cord, in an area termed Onuf's nucleus.
Urination | Anatomy of the bladder and outlet
When the sacral dorsal roots are cut in experimental animals or interrupted by diseases of the dorsal roots such as tabes dorsalis in humans, all reflex contractions of the bladder are abolished. The bladder becomes distended, thin-walled, and hypotonic, but there are some contractions because of the intrinsic response of the smooth muscle to stretch.
Urination | Deafferentation
Smooth muscle bundles pass on either side of the urethra, and these fibers are sometimes called the internal urethral sphincter, although they do not encircle the urethra. Further along the urethra is a sphincter of skeletal muscle, the sphincter of the membranous urethra (external urethral sphincter). The bladder's epithelium is termed transitional epithelium which contains a superficial layer of dome-like cells and multiple layers of stratified cuboidal cells underneath when evacuated. When the bladder is fully distended the superficial cells become squamous (flat) and the stratification of the cuboidal cells is reduced in order to provide lateral stretching.
Urination | Anatomy of the bladder and outlet
The bladder's smooth muscle has some inherent contractile activity; however, when its nerve supply is intact, stretch receptors in the bladder wall initiate a reflex contraction that has a lower threshold than the inherent contractile response of the muscle. Action potentials carried by sensory neurons from stretch receptors in the urinary bladder wall travel to the sacral segments of the spinal cord through the pelvic nerves. Since bladder wall stretch is low during the storage phase, these afferent neurons fire at low frequencies. Low-frequency afferent signals cause relaxation of the bladder by inhibiting sacral parasympathetic preganglionic neurons and exciting lumbar sympathetic preganglionic neurons.
Urination | Storage phase
In humans and other mammals, neurons in the PMC send descending excitatory projections to spinally located parasympathetic neurons controlling the detrusor muscle of the bladder and inhibitory interneurons regulating Onuf's nucleus. Additionally, the PMC receives ascending input from the level of the lumbosacral spinal cord. During bladder filling, neurons within the PMC are turned off. However, at a critical level of bladder distention the afferent information arising from mechanoreceptors in the detrusor switches the PMC on and enhances its activity. This activation results in relaxation of the male or female external urethral sphincter and contraction of the bladder. While operating as a spino bulbospinal reflex arc, this pattern of activity is also elicited through the conscious desire to urinate.
Pontine micturition center | Regulation
The wall of the urinary bladder is normally 3–5 mm thick. When well distended, the wall is normally less than 3 mm.
Urinary bladder | Structure
They then curve anteriormedially to enter the bladder through the back, at the vesicoureteric junction, running within the wall of the bladder for a few centimeters. The backflow of urine is prevented by valves known as ureterovesical valves. In the female, the ureters pass through the mesometrium on the way to the bladder.
Excretory system | Ureter
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system. The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle. Voiding urine begins with voluntary relaxation of the external urethral sphincter. This is facilitated by inhibition of the somatic neurons in Onuf's nucleus via signals arising in the pontine micturition center and traveling through the descending reticulospinal tracts. During ejaculation, the external sphincter opens and the internal sphincter closes.
External sphincter muscle of male urethra | Function
The part of the urogenital sinus related to the bladder and urethra absorbs the ends of the Wolffian ducts and the associated ends of the renal diverticula. This gives rise to the trigone of the bladder and part of the prostatic urethra. The remainder of this part of the urogenital sinus forms the body of the bladder and part of the prostatic urethra. The apex of the bladder stretches and is connected to the umbilicus as a narrow canal. This canal is initially open, but later closes as the urachus goes on to definitively form the median umbilical ligament.
Urachus | Development
Unlike the urinary bladder of vertebrates, the urinary bladder of crustaceans both stores and modifies urine. The bladder consists of two sets of lateral and central lobes. The central lobes sit near the digestive organs and the lateral lobes extend along the front and sides of the crustacean's body cavity. The tissue of the bladder is thin epithelium.
Urinary bladder | Crustaceans
With the added function of the swim bladder as a resonating chamber, signals are amplified to noticeable levels.
Weberian apparatus | Structural anatomy and function
Vesical () refers to the urinary bladder and its relevant and nearby structures and functions, including:
Vesical | Introduction
The urethra is the vessel through which urine passes after leaving the bladder. During urination, the smooth muscle lining the urethra relaxes in concert with bladder contraction(s) to forcefully expel the urine in a pressurized stream. Following this, the urethra re-establishes muscle tone by contracting the smooth muscle layer, and the bladder returns to a relaxed, quiescent state. Urethral smooth muscle cells are mechanically coupled to each other to coordinate mechanical force and electrical signaling in an organized, unitary fashion.
Urethra | Urination
The urinary bladder is the organ that collects waste excreted by the kidneys prior to disposal by urination. It is a hollow muscular, and distensible (or elastic) organ, and sits on the pelvic floor. 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 human 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.
Excretory system | Urinary bladder
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system. The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle. Voiding urine begins with voluntary relaxation of the external urethral sphincter. This is facilitated by inhibition of the somatic neurons in Onuf's nucleus via signals arising in the pontine micturition center and traveling through the descending reticulospinal tracts.
External sphincter muscle of female urethra | Function
Testing of bladder function is used in that case to show a poorly compliant bladder, with bladder neck incompetence, and fixed external sphincter tone .
Inferior hypogastric plexus | Introduction
The two main methods for replacing bladder function involve either redirecting urine flow or replacing the bladder "in situ". Replacement can be done with an artificial urinary bladder, an artificial organ.
Artificial urinary bladder | Introduction
When viewed under a microscope the bladder can be seen to have an inner lining (called epithelium), three layers of muscle fibres, and an outer adventitia. The inner wall of the bladder is called urothelium, a type of transitional epithelium formed by three to six layers of cells; the cells may become more cuboidal or flatter depending on whether the bladder is empty or full. Additionally, these are lined with a mucous membrane consisting of a surface glycocalyx that protects the cells beneath it from urine. The epithelium lies on a thin basement membrane, and a lamina propria. The mucosal lining also offers a urothelial barrier against the passing of infections.
Urinary bladder | Microanatomy
The modern Latin word for "bladder" – "cystis" – appears in associated terms such as cystitis (inflammation of the bladder).
Urinary bladder | Introduction
The main functions of the urinary system and its components are to:
Urinary system | Function
The bladder, or urinary bladder, is an organ that collects urine for excretion in animals. Bladder may also refer to:
Bladder (disambiguation) | Introduction
The two main methods for replacing bladder function involve either redirecting urine flow or replacing the bladder "in situ". Standard methods for replacing the bladder involve fashioning a bladder-like pouch from intestinal tissue. As of 2017 methods to grow bladders using stem cells had been attempted in clinical research but this procedure was not part of medicine.
Artificial organ | 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 located below the peritoneal cavity near the pelvic floor and behind the pubic symphysis. In men, it lies in front of the rectum, separated by the recto-vesical pouch, and is supported by fibres of the levator ani and of the prostate gland. In women, it 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.
Urinary bladder | Nearby structures
Related to the urinary bladder, anteriorly there are the following folds:
Umbilical folds | Introduction
Frequent urination at night may indicate the presence of bladder stones. Disorders of or related to the bladder include: Disorders of bladder function may be dealt with surgically, by re-directing the flow of urine or by replacement with an artificial urinary bladder. The volume of the bladder may be increased by bladder augmentation. An obstruction of the bladder neck may be severe enough to warrant surgery.
Urinary bladder | Incontinence and retention
The urethral cuff is deflated manually by pressing the control pump that is placed in the scrotum, allowing the patient to empty the bladder. The urethral cuff then re-inflates automatically to refill the urethral cuff and once again prevent urine from leaking.
Artificial urinary sphincter | History
The ureters are a component of the urinary system. Urine, produced by the kidneys, travels along the ureters to the bladder. It does this through regular contractions called peristalsis.
Ureter | Function
The parasympathetic nerve supply comes from the parasympathetic preganglionic neurons in the sacral spinal cord and also terminates in the longitudinal and circular smooth muscle layers. Finally the somatic nerve supply arises from the urethral sphincter motor neurons in the ventral horn of the sacral spinal cord; better known as Onuf's nucleus. The pudendal nerve that extends from Onuf's nucleus, connects directly to the rhabdosphincter muscle to control micturation. The sympathetic storage reflex or pelvic-to-hypo-gastric reflex is initiated when the bladder swells. Stretch receptors cause postganglionic neurons to release norepinephrine (NE). NE causes the bladder to relax and the urethra to contract, thus preventing urine loss.
Onuf's nucleus | Urinary stress incontinence
The bladder receives both sensory and motor supply from sympathetic and the parasympathetic nervous systems. The motor supply from both 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, relating to distension or to irritation (such as by infection or a stone) is transmitted primarily through the parasympathetic nervous system. These travel via sacral nerves to S2-4. From here, sensation travels to the brain via the dorsal columns in the spinal cord.
Urinary bladder | Nerve supply
In healthy individuals the ureters enter the urinary bladder obliquely and run submucosally for some distance. This, in addition to the ureter's muscular attachments, helps secure and support them posteriorly. Together these features produce a valvelike effect that occludes the ureteric opening during storage and voiding of urine. In people with VUR, failure of this mechanism occurs, with resultant backward (retrograde) flow of urine.
Vesicoureteral reflux | Causes
All mammals have a urinary bladder. This structure begins as an embryonic cloaca. In the vast majority, this eventually becomes differentiated into a dorsal part connected to the intestine and a ventral part which becomes associated with the urinogenital passage and urinary bladder. The only mammals in which this does not take place are the platypus and the spiny anteater both of which retain the cloaca into adulthood. The mammalian bladder is an organ that regularly stores a hyperosmotic concentration of urine. It therefore is relatively impermeable and has multiple epithelial layers. The urinary bladder of the cetaceans (whales and dolphins) is proportionally smaller than that of land-dwelling mammals.
Urinary bladder | Mammals
In this case, usually one ureter drains correctly to the bladder, with the duplicated ureter presenting as ectopic.
Ectopic ureter | Introduction
The urethra is a fibrous and muscular tube which connects the urinary bladder to the external urethral meatus. Its length differs between the sexes, because it passes through the penis in males.
Urethra | Structure
These then form 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 these vessels drain into the external iliac lymph nodes.
Urinary bladder | Blood and lymph supply
The pontine micturition center also causes inhibition of Onuf's nucleus, resulting in relaxation of the external urinary sphincter. When the external urinary sphincter is relaxed urine is released from the urinary bladder when the pressure there is great enough to force urine to flow out of the urethra. The micturition reflex normally produces a series of contractions of the urinary bladder. The flow of urine through the urethra has an overall excitatory role in micturition, which helps sustain voiding until the bladder is empty.
Urination | Voiding phase
In males it contributes to erection, the contractions of orgasm and ejaculation. In females it contributes to clitoral erection and the contractions of orgasm, and closes the vagina. This muscle serves to empty the canal of the urethra, after the bladder has expelled its contents; during the greater part of the act of micturition its fibers are relaxed, and it only comes into action at the end of the process. The middle fibers are supposed by Krause to assist in the erection of the corpus spongiosum, by compressing the erectile tissue of the bulb.
Bulbospongiosus muscle | Function
The trigone (a.k.a. vesical trigone) is a smooth triangular region of the internal urinary bladder formed by the two ureteric orifices and the internal urethral orifice. The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the brain of its need to empty. The signals become stronger as the bladder continues to fill. Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of mesodermal origin (the rest of the bladder is endodermal). In the female the mesonephric ducts regress, causing the trigone to be less prominent, but still present.
Trigone of urinary bladder | Introduction
The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut. The external urethral sphincter originates at the ischiopubic ramus and inserts into the intermeshing muscle fibers from the other side. It is controlled by the deep perineal branch of the pudendal nerve. Activity in the nerve fibers constricts the urethra.
Urethral sphincters | Introduction
The urethra (from Greek οὐρήθρα – "ourḗthrā") is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra connects to the urinary meatus above the vagina, whereas in marsupials, the female's urethra empties into the urogenital sinus. Females use their urethra only for urinating, but males use their urethra for both urination and ejaculation. The external urethral sphincter is a striated muscle that allows voluntary control over urination. The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the sympathetic division of the autonomic nervous system.
Urethra | Introduction
Pig bladder (also pig's bladder) is the urinary bladder of a domestic pig, similar to the human urinary bladder. Today, this hollow organ has various applications in medicine, and in traditional cuisines and customs. Historically, the pig bladder had several additional uses, all based on its properties as a lightweight, stretchable container that could be filled and tied off.
Pig bladder | Introduction
The urachus is a fibrous remnant of the allantois, a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord. The fibrous remnant lies in the space of Retzius, between the transverse fascia anteriorly and the peritoneum posteriorly.
Urachus | Introduction
The detrusor muscle, also detrusor urinae muscle, muscularis propria of the urinary bladder and (less precise) muscularis propria, is smooth muscle found in the wall of the bladder. The detrusor muscle remains relaxed to allow the bladder to store urine, and contracts during urination to release urine. Related are the urethral sphincter muscles which envelop the urethra to control the flow of urine when they contract. In older adults over 60 years in age, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention.
Detrusor muscle | Introduction
Stress urinary incontinence (SUI) is a common disease in women caused by pelvic floor muscle weakness. Coughing, laughing, sneezing, exercising or other movements that increase intra-abdominal pressure, and thus increase pressure on the bladder, are common reasons for urine loss. There are three layers of muscle that are known to control urine flow through the urethra; an inner band of longitudinal smooth muscle, a middle band of circular smooth muscle, and an external band of striated muscle called the rhabdosphincter. The urethra is controlled by the sympathetic, parasympathetic, and somatic divisions of the peripheral nervous system. The sympathetic innervation (nerve supply) comes from the sympathetic preganglionic neurons located in the upper lumbar spinal cord along the hypogastric nerve and terminates in the longitudinal and circular smooth muscle layers in the urethra.
Onuf's nucleus | Urinary stress incontinence
As the female external urethral opening (meatus) is also situated between labia minora, they may play a role in guiding the stream of the urine during female urination.
Labia minora | Functioning
Over time, as the bladder enlarges, it absorbs the surrounding parts of the primitive ureters. Finally, the entry points of the ureters into the bladder move upwards, owing to the upward migration of the kidneys in the developing embryo.
Ureter | Development
Cystometrogram shows large bladder capacity and absence of sensations during the filling phase. The maximum urethral closure pressure (MUCP) is raised. The diagnosis is done by testing the electromyographic (EMG) activity of external striated urethral sphincter. The usual findings are complex repetitive discharges without and with deceleration (decelerating bursts), suggesting an impairment in sphincter muscle relaxation.
Fowler's syndrome | Diagnosis
As distinct from the Western medical concept of urinary bladder, this concept from traditional Chinese medicine is more a way of describing a set of interrelated functions than an anatomical organ. (See Zang Fu theory) The Bladder is a Yang (Fu) organ; its paired Yin (Zang) organ is the Kidney. Both are associated with the element of water and the emotion of fear. As opposed to western medicine, where the bladders function is the storage and excretion of urine, the bladder in traditional Chinese medicine has extended functions, including how fluids are transformed during urine production. Fluids are still sent from the small intestine to the bladder for storage, but the bladder's capabilities are dependent on the kidney yang.
Urinary bladder (Chinese medicine) | Introduction
Urine storage and elimination (urination) requires coordination between the bladder emptying muscle (detrusor) and the external sphincter of the bladder. This coordination can be disrupted by damage or diseases of the central nervous system, peripheral nerves or autonomic nervous system. This includes any condition that impairs bladder signaling at any point along the path from the urination center in the brain, spinal cord, peripheral nerves and the bladder.
Neurogenic bladder dysfunction | Causes
When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while. Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra. The bladder becomes shrunken and the bladder wall hypertrophied. The reason for the difference between the small, hypertrophic bladder seen in this condition and the distended, hypotonic bladder seen when only the afferent nerves are interrupted is not known. The hyperactive state in the former condition suggests the development of denervation hypersensitization even though the neurons interrupted are preganglionic rather than postganglionic.
Urination | Denervation
At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder. At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge. When the individual is ready to urinate, he or she consciously initiates voiding, causing the bladder to contract and the outlet to relax. Voiding continues until the bladder empties completely, at which point the bladder relaxes and the outlet contracts to re-initiate storage. The muscles controlling micturition are controlled by the autonomic and somatic nervous systems. During the storage phase the internal urethral sphincter remains tense and the detrusor muscle relaxed by sympathetic stimulation.
Urination | Physiology
From here, in males they cross under the vas deferens and in front of the seminal vesicles to enter the bladder near the trigone. In females, the ureters pass behind the ovaries, and then travel in the lower midline section of the broad ligament of the uterus. For a short part, the uterine arteries travel on top for a short (2.5 cm) period. They then pass by the cervix, travelling inwards towards the bladder.
Ureter | Structure
Conversely, afferent input causes contraction of the sphincter through excitation of Onuf's nucleus, and contraction of the bladder neck and urethra through excitation of the sympathetic preganglionic neurons. Diuresis (production of urine by the kidney) occurs constantly, and as the bladder becomes full, afferent firing increases, yet the micturition reflex can be voluntarily inhibited until it is appropriate to begin voiding.
Urination | Storage phase
A voiding cystourethrography study uses contrast dye to obtain images of the bladder both when it is full and after urination which can show changes in bladder shape consistent with neurogenic bladder. Urodynamic studies are an important component of the evaluation for neurogenic bladder. Urodynamics refers to the measurement of the pressure-volume relationship in the bladder. The bladder usually stores urine at low pressure and urination can be completed without a dramatic pressure rise. Damage to the kidneys is probable if the pressure rises above 40 cm of water during filling. Bladder pressure can be measured by cystometry, during which the bladder is artificially filled with a catheter and bladder pressures and detrusor activity are monitored.
Neurogenic bladder dysfunction | Diagnosis
A ureterocele is a cystic dilation of the end of the ureter that can occur in the bladder and/or in the urethra. It occurs in approximately 1 in every 5000 live births, is most commonly seen in females and involves both ides of the urinary tract in approximately half of cases.
Bladder outlet obstruction | Ureterocele
In flaccid bladder (also known as lower motor neuron or hypotonic bladder), the muscles of the bladder lose ability to contract normally. This can cause the inability to void urine even if the bladder is full and cause a large bladder capacity. The internal urinary sphincter can contract normally, however urinary incontinence is common. This type of neurogenic bladder is caused by damage to the peripheral nerves that travel from the spinal cord to the bladder.
Neurogenic bladder dysfunction | Flaccid
The trapping mechanism of "Utricularia" is purely mechanical; no reaction from the plant (irritability) is required in the presence of prey, in contrast with the triggered mechanisms employed by Venus flytraps ("Dionaea"), waterwheels ("Aldrovanda"), and many sundews ("Drosera"). The only active mechanism involved is the constant pumping out of water through the bladder walls by active transport. As water is pumped out, the bladder's walls are sucked inwards by the partial vacuum created, and any dissolved material inside the bladder becomes more concentrated. The sides of the bladder bend inwards, storing potential energy like a spring. Eventually, no more water can be extracted, and the bladder trap is 'fully set' (technically, osmotic pressure rather than physical pressure is the limiting factor).
Utricularia | Trapping mechanism
The indwelling has the same function, however it is designed to remain in the bladder.
Dyssynergia | Catheterization
The ampulla of ductus deferens is an enlargement of the ductus deferens at the fundus of the bladder which acts as a reservoir for sperm. This structure is seen in some mammalian and squamate species and is sometimes tortuous in shape.
Ampulla of ductus deferens | Introduction
The ureter is lined by urothelium, a type of transitional epithelium that is capable of responding to stretches in the ureters. The transitional epithelium may appear as a layer of column-shaped cells when relaxed, and of flatter cells when distended. Below the epithelium sits the lamina propria. The lamina propria is made up of loose connective tissue with many elastic fibers interspersed with blood vessels, veins and lymphatics. The ureter is surrounded by two muscular layers, an inner longitudinal layer of muscle, and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer.
Ureter | Microanatomy
The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In the human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epithelium, and has an additional smooth muscle layer in third closest to the bladder that assists with peristalsis. The ureters can be affected by a number of diseases; including urinary tract infections and kidney stone. is when a ureter is narrowed, due to for example chronic inflammation. Congenital abnormalities that affect the ureters can include the development of two ureters on the same side, or abnormally placed ureters.
Ureter | Introduction
The pore is surrounded by small, irregularly shaped lobes; and the excretory duct is directed forward. The rectum and anus are atrophied or absent; non-functional.
Tylenchulus semipenetrans | Morphology
As the bladder fills, rising pressure compresses the channel against the bladder wall, creating a one-way valve that prevents leakage of urine between catheterizations.
Mitrofanoff procedure | Introduction
In spastic neurogenic bladder (also known as upper motor neuron or hyper-reflexive bladder), the muscle of the bladder (detrusor) and urethral sphincter do not work together and are usually tightly contracted at the same time. This phenomenon is also called detrusor external sphincter dyssynergia (DESD). This leads to urinary retention with high pressures in the bladder that can damage the kidneys. The bladder volume is usually smaller than normal due to increased muscle tone in the bladder. Spastic neurogenic bladder is usually caused by damage to the spinal cord above the level of the 10th thoracic vertebrae (T10).
Neurogenic bladder dysfunction | Spastic
Kidneys and ureters located in incorrect position, including horseshoe kidney and ectopic ureters.
Bladder outlet obstruction | Anomalies of position
The anatomy of the human urinary system differs between males and females at the level of the urinary bladder. In males, the urethra begins at the internal urethral orifice in the trigone of the bladder, continues through the external urethral orifice, and then becomes the prostatic, membranous, bulbar, and penile urethra. Urine exits through the external urethral meatus. The female urethra is much shorter, beginning at the bladder neck and terminating in the vaginal vestibule.
Urinary system | Structure
Elsewhere, at a similar structure known as the "oval window", the bladder is in contact with blood and the oxygen can diffuse back out again. Together with oxygen, other gases are salted out in the swim bladder which accounts for the high pressures of other gases as well.
Swim bladder | Structure and function
The swim bladder normally consists of two gas-filled sacs located in the dorsal portion of the fish, although in a few primitive species, there is only a single sac. It has flexible walls that contract or expand according to the ambient pressure. The walls of the bladder contain very few blood vessels and are lined with guanine crystals, which make them impermeable to gases. By adjusting the gas pressurising organ using the gas gland or oval window the fish can obtain neutral buoyancy and ascend and descend to a large range of depths. Due to the dorsal position it gives the fish lateral stability.
Swim bladder | Structure and function
Upper urinary tract obstruction includes the renal pelvis and upper ureters.
Bladder outlet obstruction | Upper urinary tract obstruction
When nerves to the back are damaged, the bladder cannot empty, resulting in stagnant urine.
Bladder stone | Signs and symptoms
In order to introduce gas into the bladder, the gas gland excretes lactic acid and produces carbon dioxide. The resulting acidity causes the hemoglobin of the blood to lose its oxygen (Root effect) which then diffuses partly into the swim bladder. The blood flowing back to the body first enters a rete mirabile where virtually all the excess carbon dioxide and oxygen produced in the gas gland diffuses back to the arteries supplying the gas gland. Thus a very high gas pressure of oxygen can be obtained, which can even account for the presence of gas in the swim bladders of deep sea fish like the eel, requiring a pressure of hundreds of bars.
Swim bladder | Structure and function
This action in the male may be directly or indirectly associated with stimulation of the prostate gland and some types of bladder control.
Urethral sounding | Introduction
The smooth muscle cells in the urinary bladder express β-AR. They have effect on the detrusor muscle which relaxes when the β-AR are activated. The relaxed detrusor muscle improves filling capacity of the bladder and eases the urge to pass urine.
Beta3-adrenergic agonist | Mechanism of action
Lower urinary tract obstruction involves the lower ureters, urinary bladder and the urethra.
Bladder outlet obstruction | Lower urinary tract obstruction
During storage, bladder pressure stays low, because of the bladder's highly compliant nature. A plot of bladder (intravesical) pressure against the depressant of fluid in the bladder (called a cystometrogram), will show a very slight rise as the bladder is filled. This phenomenon is a manifestation of the law of Laplace, which states that the pressure in a spherical viscus is equal to twice the wall tension divided by the radius. In the case of the bladder, the tension increases as the organ fills, but so does the radius. Therefore, the pressure increase is slight until the organ is relatively full.
Urination | Storage phase
Spasms of the internal urethral sphincter are associated with penile erection. Because the internal urethral sphincter is under involuntary control, it is believed to play a role in paruresis, in which a person who perceives oneself to be under observation is unable to urinate.
Internal urethral sphincter | Function
In some of the bladder reconstructions, the bladder is augmented with the addition of a segment of the large intestines to increase the volume capacity of the reconstructed bladder. (http://www.med.umich.edu/1libr/urology/BladderAugmentation.pdf) In the complete primary repair of exstrophy (CPRE) the bladder closure is combined with an epispadias repair, in an effort to decrease costs and morbidity. This technique has, however, led to significant loss of penile and corporal tissue, particularly in younger patients. In females treatment has included: Surgical reconstruction of the clitoris which is separated into two distinct bodies. Surgical reconstruction to correct the split of the mons, redefine the structure of the bladder neck and urethra.
Bladder exstrophy | Surgery
the bladder wall may show trabeculations or sacculations or even diverticuli. Diagnosis can also be made by cystoscopy, where a small camera is inserted into the urethra for direct visualization of the posteriorly positioned valve. A limitation of this technique is that posterior valve tissue is translucent and can be pushed against the wall of the urethra by inflowing irrigation fluid, making it difficult to visualize. Cystoscopy may also demonstrate the bladder changes.
Posterior urethral valve | Diagnosis
The gold standard for all urinary incontinence is an urodynamic study that looks for bladder capacity, detrusor stability, contractility, and voiding ability (cystometry). Bethanechol (Management of overflow incontinence by activating muscarinic receptors in the bladder and stimulating contraction to void the urine, NOT a treatment modality; must rule out urinary obstruction prior to use.) If an incontinence is due to overflow incontinence, in which the bladder never empties completely, or if the bladder cannot empty because of poor muscle tone, past surgery, or spinal cord injury, a catheter may be used to empty the bladder. A catheter is a tube that can be inserted through the urethra into the bladder to drain urine.
Overflow incontinence | Diagnosis
The ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the human adult, the ureters are usually 25–30 cm (10–12 in) long. In humans, the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle. The ureters cross the pelvic brim near the bifurcation of the iliac arteries (which they run over). This "pelviureteric junction" is a common site for the impaction of kidney stones (the other being the uteterovesical valve). The ureters run posteriorly on the lateral walls of the pelvis.
Excretory system | Ureter
The internal urethral orifice is the opening of the urinary bladder into the urethra. It is placed at the apex of the trigonum vesicae, in the most dependent part of the bladder, and is usually somewhat crescent-shaped; the mucous membrane immediately behind it presents a slight elevation in males, the uvula vesicae, caused by the middle lobe of the prostate.
Internal urethral orifice | Introduction
The cells lining the urethra (the epithelium) start off as transitional cells as it exits the bladder, which are variable layers of flat to cuboidal cells that change shape depending on whether they are compressed by the contents of the urethra. Further along the urethra there are pseudostratified columnar and stratified columnar epithelia. The lining becomes multiple layers of flat cells near the end of the urethra, which is the same as the external skin around it. There are small mucus-secreting urethral glands, as well as bulbo-urethral glands of Cowper, that secret mucous acting to lubricate the urethra. The urethra consists of three coats: muscular, erectile, and mucous, the muscular layer being a continuation of that of the bladder.
Urethra | Microanatomy
In the developing embryo, at the hind end lies a cloaca. This, over the fourth to the seventh week, divides into a urogenital sinus and the beginnings of the anal canal, with a wall forming between these two inpouchings called the urorectal septum. The urogenital sinus divides into three parts, with the upper and largest part becoming the bladder; the middle part becoming the urethra, and the lower part changes depending on the biological sex of the embryo. The human urinary bladder derives from the urogenital sinus, and it is initially continuous with the allantois. The upper and lower parts of the bladder develop separately and join together around the middle part of development.
Urinary bladder | Development
In IC, PPS is believed to work by providing a protective coating to the damaged bladder wall. PPS is similar in structure to the natural glycosaminoglycan coating of the inner lining of the bladder, and may replace or repair the lining, reducing its permeability.
Pentosan polysulfate | Mechanism of action
The urethral sponge is composed of erectile tissue; during arousal, it becomes swollen with blood, compressing the urethra, helping, along with the pubococcygeus muscle, to prevent urination during sexual activity.
Urethral sponge | Functions
Initially, a thin tube (catheter) is placed through the skin just above the pubic bone into the bladder, often with the assistance of ultrasound imaging. This catheter initially remains in place for up to a month while the tissue around it scars and forms a tract (sinus) between the bladder and the body exterior. After the formation of scar tissue is complete, the catheter is replaced periodically in order to help prevent infection.
Suprapubic cystostomy | Introduction