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.
Mammals
Urinary bladder
Urinary bladder | Mammals
Yes, all mammals have a urinary bladder Yes. All mammals have a urinary bladder. Yes. The mammalian bladder is an organ that regularly stores a hyperosmotic concentration of urine Yes
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
Urine, excreted by the kidneys, collects in the bladder
assistant
do mammals also have this bladder?
user
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
The bladder, or urinary bladder, is an organ that collects urine for excretion in animals. Bladder may also refer to:
Bladder (disambiguation) | Introduction
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
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
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
In nearly all bird species, there is no urinary bladder per se. Although all birds have kidneys, the ureters open directly into a cloaca which serves as a reservoir for urine, fecal matter, and eggs.
Urinary bladder | Birds
In all reptiles, the urinogenital ducts and the anus both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards but is lacking in the monitor lizard, the legless lizards. It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders. Charles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight. Such adaptations are the result of environments such as remote islands and deserts where water is very scarce.
Urinary bladder | Reptiles
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 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
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
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
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
All vertebrates have two kidneys located behind the abdomen that produce urine, and have a way of excreting it, so that waste products within the urine can be removed from the body. The structure specifically called the ureter is present in amniotes, meaning mammals, birds and reptiles. These animals possess an adult kidney derived from the metanephros. The duct that connects the kidney to excrete urine in these animals is the ureter. It connects to the urinary bladder, from whence urine leaves via the urethra.
Ureter | Other animals
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
In all reptiles the urinogenital ducts and the anus both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards, but is lacking in the monitor lizard, the legless lizards. It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders. Charles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight. Such adaptations are the result of environments such as remote islands and deserts where water is very scarce.
Reptile | Excretion
Other desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in osmoregulation. Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity. Their bladder is also usually bilobed with a left and right section. The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi.
Urinary bladder | Reptiles
Most aquatic and semi-aquatic amphibians have a membranous skin which allows them to absorb water directly through it. Some semi-aquatic animals also have similarly permeable bladder membrane. As a result, they tend to have high rates of urine production to offset this high water intake, and have urine which is low in dissolved salts. The urinary bladder assists such animals to retain salts. Some aquatic amphibian such as "Xenopus" do not reabsorb water, to prevent excessive water influx. For land-dwelling amphibians, dehydration results in reduced urine output. The amphibian bladder is usually highly distensible and among some land-dwelling species of frogs and salamanders may account for between 20% and 50% of their total body weight.
Urinary bladder | Amphibians
Vesical () refers to the urinary bladder and its relevant and nearby structures and functions, including:
Vesical | Introduction
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
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
Even within the Vertebrata there are morphological variants with specific terminology, such as hemipenes. In most species of animals in which there is an organ that might reasonably be described as a penis, it has no major function other than intromission, or at least conveying the sperm to the female, but in the placental mammals the penis bears the distal part of the urethra, which discharges both urine during urination and semen during copulation.
Penis | Introduction
Reptilian nephrons are more abundant but lack the distinctive loops of Henle seen in mammals. The urine collected by the kidney is emptied into the cloaca through the ureters and then to the colon by reverse peristalsis.
Bird anatomy | Kidney
Other desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in osmoregulation.
Reptile | Excretion
Related to the urinary bladder, anteriorly there are the following folds:
Umbilical folds | Introduction
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
The fetal pig's urogenital system is similar to the adult pig's system with the exception of the reproductive organs. The fetal pig urinary tract is relatively developed and easy to locate during dissection. The kidneys are located behind the abdominal organs and are partially embedded into the dorsal body wall by the spine. The ureters carry the urine to the urinary bladder, the large sack-like organ by the umbilical artery and vein, to the urethra. From there, the urine can be excreted.
Fetal pig | Urogenital
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
In many other animals a single posterior orifice, called the cloaca, serves as the only opening for the reproductive, digestive, and urinary tracts (if present). All amphibians, birds, reptiles, some fish, and a few mammals (monotremes, tenrecs, golden moles, and marsupial moles) have this orifice, from which they excrete both urine and feces in addition to serving reproductive functions. Excretory systems with analogous purpose in certain invertebrates are also sometimes referred to as cloacae.
Sex organ | Other animals
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
The urine passes along paired ureters to the urinary bladder from which it is vented periodically into the cloaca. All bodily wastes exit the body through the cloaca which terminates in a cloacal vent.
Frog | Digestion and excretion
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
The kidney in animal anatomy is a part of the urinary system. Kidney may also refer to:
Kidney (disambiguation) | Introduction
The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their current water depth without having to waste energy in swimming. Also, the dorsal position of the swim bladder means the center of mass is below the center of volume, allowing it to act as a stabilizing agent. Additionally, the swim bladder functions as a resonating chamber, to produce or receive sound. The swim bladder is evolutionarily homologous to the lungs. Charles Darwin remarked upon this in "On the Origin of Species".
Swim bladder | Introduction
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
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 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
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
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
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
The main functions of the urinary system and its components are to:
Urinary system | Function
The modern Latin word for "bladder" – "cystis" – appears in associated terms such as cystitis (inflammation of the bladder).
Urinary bladder | Introduction
The internal sphincter is present both in males and females.
Urethra | Introduction
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 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
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
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
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
It is separated from the uterus by the vesicouterine excavation. In infants and young children, the urinary bladder is in the abdomen even when empty.
Excretory system | Urinary bladder
Excretion is performed mainly by two small kidneys. In diapsids, uric acid is the main nitrogenous waste product; turtles, like mammals, excrete mainly urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure called a loop of Henle, which is present in the nephrons of birds and mammals. Because of this, many reptiles use the colon to aid in the reabsorption of water. Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt glands in some reptiles.
Reptile | Excretion
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
This means the urethra, a compressible tube used for urination, runs through the middle of the prostate. This leads to an evolutionary design fault for some mammals, including human males. The prostate is prone to infection and enlargement later in life, constricting the urethra so urinating becomes slow and painful.
Prostate | Other animals
The urinary bladder collects and stores the urine until urination. The urine collected in the bladder is passed into the external environment from the body through an opening called the urethra.
Excretory system | Urinary system
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 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
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
The gills of most teleost fish help to eliminate ammonia from the body, and fish live surrounded by water, but most still have a distinct bladder for storing waste fluid. The urinary bladder of teleosts is permeable to water, though this is less true for freshwater dwelling species than saltwater species. Most fish also have an organ called a swim-bladder which is unrelated to the urinary bladder except in its membranous nature. The loaches, pilchards, and herrings are among the few types of fish in which a urinary bladder is poorly developed. It is largest in those fish which lack an air bladder, and is situated in front of the oviducts and behind the rectum.
Urinary bladder | Fish
In the latter, the gas content of the bladder is controlled through a rete mirabilis, a network of blood vessels affecting gas exchange between the bladder and the blood.
Fish anatomy | Swim bladder
The whale kidney is adapted to excreting excess salt; however, while producing urine more concentrated than seawater, it wastes a lot of water which must be replaced. Baleen whales have a relatively small brain compared to their body mass. Like other mammals, their brain has a large, folded cerebrum, the part of the brain responsible for memory and processing sensory information. Their cerebrum only makes up about 68% of their brain's weight, as opposed to human's 83%. The cerebellum, the part of the brain responsible for balance and coordination, makes up 18% of their brain's weight, compared to 10% in humans, which is probably due to the great degree of control necessary for constantly swimming.
Baleen whale | Internal systems
Darwin reasoned that the lung in air-breathing vertebrates had derived from a more primitive swim bladder. In the embryonic stages, some species, such as redlip blenny, have lost the swim bladder again, mostly bottom dwellers like the weather fish. Other fish—like the opah and the pomfret—use their pectoral fins to swim and balance the weight of the head to keep a horizontal position. The normally bottom dwelling sea robin can use their pectoral fins to produce lift while swimming.
Swim bladder | Introduction
This adaptation can be the result of environmental pressures and behavioral factors. As a result of this organ, they are extremely resilient and able to tolerate conditions that most other fish could not survive.
Gar | Swim bladder
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
With a few exceptions noted below, mammals have no cloaca. Even in those that have one, the cloaca is partially subdivided into separate regions for the anus and urethra.
Cloaca | Mammals
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
While the primary purpose of urination is the same across the animal kingdom, urination often serves a social purpose beyond the expulsion of waste material. In dogs and other animals, urination can mark territory or express submissiveness. In small rodents such as rats and mice, it marks familiar paths. The urine of animals of differing physiology or sex sometimes has different characteristics. For example, the urine of birds and reptiles is whitish, consisting of a pastelike suspension of uric acid crystals, and discharged with the feces of the animal via the cloaca, whereas mammals' urine is a yellowish colour, with mostly urea instead of uric acid, and is discharged via the urethra, separately from the feces.
Urination | Other species
Amphibians possess a pancreas, liver and gall bladder. The liver is usually large with two lobes. Its size is determined by its function as a glycogen and fat storage unit, and may change with the seasons as these reserves are built or used up. Adipose tissue is another important means of storing energy and this occurs in the abdomen (in internal structures called fat bodies), under the skin and, in some salamanders, in the tail. There are two kidneys located dorsally, near the roof of the body cavity. Their job is to filter the blood of metabolic waste and transport the urine via ureters to the urinary bladder where it is stored before being passed out periodically through the cloacal vent.
Amphibian | Digestive and excretory systems
On the medial side of the Wolffian duct, from the sixth cervical to the third lumbar segments, a series of tubules, the Wolffian tubules, develops. They increase in number by outgrowths from the original tubules. They change from solid masses of cells to instead become hollowed in the center. One end grows toward and finally opens into the Wolffian duct, the other dilates and is invaginated by a tuft of capillary bloodvessels to form a glomerulus. The tubules collectively constitute the mesonephros. The mesonephros persists and form the permanent kidneys in fish and amphibians, but in reptiles, birds, and mammals, it atrophies and for the most part disappears rapidly as the permanent kidney (metanephros) develops beginning during the sixth or seventh week, so that by the beginning of the fifth month only the ducts and a few of the tubules of the mesonephros remain.
Development of the urinary system | Mesonephros
In many mammals (including mice, guinea pigs, dogs, and opossums), the smooth muscle around the ampulla of Vater does not form a sphincter.
Sphincter of Oddi | Other animals
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
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
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
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
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
Indeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in the adult. In the most primitive vertebrates, the hagfish and lampreys, the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct. Invertebrates may possess excretory organs that are sometimes referred to as "kidneys", but, even in "Amphioxus", these are never homologous with the kidneys of vertebrates, and are more accurately referred to by other names, such as nephridia. In amphibians, kidneys and the urinary bladder harbour specialized parasites, monogeneans of the family Polystomatidae.
Kidney | Other animals
The urinary bladder is formed partly from the endodermal cloaca and partly from the ends of the Wolffian ducts. In other words, the allantois takes no share in its formation. After the separation of the rectum from the dorsal part of the cloaca, the ventral part becomes the primary urogenital sinus. The urogenital sinus, in turn, divides into the superficial definitive urogenital sinus and the deeper anterior vesico-urethral portion.
Development of the urinary system | Urinary bladder
In both the male and the female the mesonephric duct develops into the trigone of urinary bladder, a part of the bladder wall. However, further development differentiates between the sexes in the development of the urinary and reproductive organs.
Mesonephric duct | Development
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
With the added function of the swim bladder as a resonating chamber, signals are amplified to noticeable levels.
Weberian apparatus | Structural anatomy and function
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
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
In the majority of vertebrates, the mesonephros persists into the adult, albeit usually fused with the more advanced metanephros; only in amniotes is the mesonephros restricted to the embryo. The kidneys of fish and amphibians are typically narrow, elongated organs, occupying a significant portion of the trunk. The collecting ducts from each cluster of nephrons usually drain into an "archinephric duct", which is homologous with the vas deferens of amniotes. However, the situation is not always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the bladder or cloaca.
Kidney | Other animals
The kidneys of reptiles consist of a number of lobules arranged in a broadly linear pattern. Each lobule contains a single branch of the ureter in its centre, into which the collecting ducts empty. Reptiles have relatively few nephrons compared with other amniotes of a similar size, possibly because of their lower metabolic rate.
Kidney | Other animals
To properly assess the microbiome of the bladder as opposed to the genitourinary system, the urine specimen should be collected directly from the bladder, which is often done with a catheter.
Human microbiome | Urethra and bladder
Like other saccopharyngiforms, these fish have large mouths and long, slender bodies with long tails that have a bioluminescent organ at the tip. The function of this organ is currently unknown. "Saccopharynx ampullaceus" lacks a traditional gas-filled swim bladder, presumably due to the pressures at the depths they live in. Instead, the function of the swim bladder has been replaced by lymphatic spaces that run along the spine which are filled with a gelatinous substance. This gelatinous substance is thought to be maintained by the eel's aglomerular kidney.
Saccopharynx ampullaceus | Physical characteristics
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
Like most platyhelminthes, aspidogastreans use flame cells as an excretory mechanism. The two excretory bladders are located dorsally, on the anterior side of the posterior sucker, connected to ducts, and three flame cell "bulbs" on each side of the body; the ducts contain cilia to aid the flow of excreta.
Aspidogastrea | Excretory system
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
In physostomous swim bladders, a connection is retained between the swim bladder and the gut, the pneumatic duct, allowing the fish to fill up the swim bladder by "gulping" air. Excess gas can be removed in a similar manner. In more derived varieties of fish (the physoclisti) the connection to the digestive tract is lost. In early life stages, these fish must rise to the surface to fill up their swim bladders; in later stages, the pneumatic duct disappears, and the gas gland has to introduce gas (usually oxygen) to the bladder to increase its volume and thus increase buoyancy.
Swim bladder | Structure and function
The gubernaculum is present only during the development of the urinary and reproductive organs, being replaced by distinct vestiges in males and females.
Gubernaculum | Adult structures
Mups can also function as signals between different species: mice display an instinctive fear response on the detection of Mups derived from predators such as cats and rats.
Major urinary proteins | Introduction
The pronephros disappears very early; the structural elements of the mesonephros mostly degenerate, but the gonad is developed in their place, with which the Wolffian duct remains as the duct in males, and the Müllerian as that of the female. Some of the tubules of the mesonephros form part of the permanent kidney.
Development of the urinary system | Introduction
This aim was unsuccessful but as part of this work he developed a double lumen bladder catheter and devised special forceps to enable the removal of urinary stones. Hales's work on the growth pattern of long bones, demonstrating epiphyseal growth; his demonstration of spinal reflexes in the frog and his suggestion that electricity played a role in allowing nerves to control muscle function are also noteworthy.
Stephen Hales | Animal physiology
The ureters develop from the ureteric buds, which are outpouchings from the mesonephric duct. This is a duct, derived from mesoderm, found in the early embryo. Over time, the buds elongate, moving into surrounding mesodermal tissue, dilate, and divide into left and right ureters. Eventually, successive divisions from these buds form not only the ureters, but also the pelvis, major and minor calyces, and collecting ducts of the kidneys. The mesonephric duct is connected with the cloaca, which over the course of development splits into a urogenital sinus and the anorectal canal. The urinary bladder forms from the urogenital sinus.
Ureter | Development
Unlike most other mammals, female spotted hyenas have a urinary meatus that is located on the clitoral glans.
Urinary meatus | In other mammals
The ureters leave the ventral caudomedial surface and continue caudally, near the midline into the opening of the urodeum of the cloaca. Although there is no bladder, a dilated pouch of ureter stores the urine until it is secreted continuously down from the ureters to the urodeum until discharged.
Common ostrich | System overview
It also has pairs of digestive glands similar to those of basal arthropods.
Megadictyon | Introduction
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
Between the fourth and seventh weeks of development, the urorectal septum divides the cloaca into the urogenital sinus and the anal canal. The upper part of the urogenital sinus forms the bladder, while the lower part forms the urethra.
Human embryonic development | Bladder and urethra
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
Monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes via the therapsids. Marsupials have a single orifice for excreting both solids and liquids and, in females, a separate vagina for reproduction. Female placental mammals have completely separate orifices for defecation, urination, and reproduction; males have one opening for defecation and another for both urination and reproduction, although the channels flowing to that orifice are almost completely separate. The development of the anus was an important stage in the evolution of multicellular animals. It appears to have happened at least twice, following different paths in protostomes and deuterostomes.
Anus | Introduction
The pore immediately closes behind the prey, which is then digested by enzymes within the bladder. The process of trapping the prey from opening to closing the pore takes place in 0.002 seconds. If large prey becomes stuck in the pore, the prey is digested by the enzymes bit by bit until the pore closes again.
Utricularia macrorhiza | Description