The urinary bladder, or simply bladder, is a

hollow organ In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s and other

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

s that stores

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

from the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...

s before disposal by

urination Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

. In humans the bladder is a distensible organ that sits on the

pelvic floor The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...

. Urine enters the bladder via the

ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epit ...

s and exits via the

urethra 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 con ...

. The typical adult 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 The vesical veins are veins in the pelvis that drain blood from the urinary bladder. The vesical veins receive blood from the vesical venous plexus The vesical plexus envelops the lower part of the bladder and the base of the prostate The ...

. The modern Latin word for "bladder" – ''cystis'' – appears in associated terms such as

cystitis A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

(inflammation of the bladder).

Structure

In humans, the bladder is a hollow muscular organ situated at the base of the

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

. In

gross anatomy Gross anatomy is the study of anatomy at the visible or macroscopic level. The counterpart to gross anatomy is the field of histology, which studies microscopic anatomy. Gross anatomy of the human body or other animals seeks to understand the rel ...

, the bladder can be divided into a broad , a body, an apex, and a neck. The apex (also called the vertex) is directed forward toward the upper part of the

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubic ...

, and from there the

median umbilical ligament In human anatomy, the median umbilical ligament is an unpaired midline ligamentous structure upon the lower inner surface of the anterior abdominal wall. It is covered by the median umbilical fold. The median umbilical ligament represents the re ...

continues upward on the back of the anterior abdominal wall to the umbilicus. The

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesoth ...

is carried by it from the apex on to the

abdominal wall In anatomy, the abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the anterolateral and posterior walls. There is a common set of layers covering and forming all the walls: the deepest being the v ...

to form the middle umbilical fold. The neck of the bladder is the area at the base of the

trigone Trigone may refer to: * Trigone of the lateral ventricle * Trigone of urinary bladder 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 ure ...

that surrounds the

internal urethral orifice 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 immedi ...

that leads to the urethra. In males the neck of the urinary bladder is next to the

prostate gland The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physio ...

. The bladder has three openings. The two

s enter the bladder at ureteric orifices, and the

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 Vesicoureteral reflux (VUR), also known as vesicoureteric reflux, is a condition in which urine flows retrograde, or backward, from the bladder into one or both ureters and then to the renal calyx or kidneys. Urine normally travels in one directi ...

. 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 Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

that forms the floor of the bladder above the urethra. 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 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 stor ...

is the muscular layer of the wall made of

fibers Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...

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 Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

, and it stays relaxed whilst the bladder is filling. The wall of the urinary bladder is normally 3–5 mm thick. When well distended, the wall is normally less than 3 mm.

Nearby structures

In men, the

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 The peritoneal cavity is a potential space between the parietal peritoneum (the peritoneum that surrounds the abdominal wall) and visceral peritoneum (the peritoneum that surrounds the internal organs). The parietal and visceral peritonea are lay ...

near the

and behind the

. In men, it lies in front of the rectum, separated by the recto-vesical pouch, and is supported by fibres of the

levator ani The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of the ...

and of the prostate gland. In women, it lies in front of the

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...

, separated by the

vesico-uterine pouch In human female anatomy, the vesicouterine pouch, also uterovesicle pouch, is a fold of peritoneum over the uterus and the bladder. Like the rectouterine pouch, it is a female pelvic recess, but shallower and closer to the anterior fornix of the ...

, and is supported by the elevator ani and the upper part of the vagina.Page 12
in:

Blood and lymph supply

The bladder receives blood by the

vesical arteries Vesical arteries are variable in number. They supply the bladder and terminal ureter. The two most prominent are the superior vesical artery and the inferior vesical artery. The superior vesical artery comes off of the internal iliac artery and some ...

and drained into a network of

. The

superior vesical artery The superior vesical artery supplies numerous branches to the upper part of the bladder. This artery often also gives branches to the vas deferens and can provide minor collateral circulation for the testicles. Anatomy The superior vesical artery ...

supplies blood to the upper part of the bladder. The lower part of the bladder is supplied by the

inferior vesical artery The inferior vesical artery (or inferior vesicle artery) is an artery of the pelvis which arises from the internal iliac artery and supplies parts of the urinary bladder as well as other structures of the urinary system and structures of the male r ...

, both of which are branches of the

internal iliac arteries The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis. Structure The internal iliac artery supplies the walls and viscera of the pelvis, the buttock, the reproductive organs, and the medial compart ...

. In females, the

uterine The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the hollow organ, organ in the female reproductive system, reproductive system of most female mammals, including humans that accommodates the embryonic development, embryonic an ...

and

vaginal arteries The vaginal artery is an artery in females that supplies blood to the vagina and the base of the bladder. Structure The vaginal artery is usually a branch of the internal iliac artery. Some sources say that the vaginal artery can arise from the ...

provide additional blood supply. Venous drainage begins in a network of small vessels on the lower surfaces of the bladder, which coalesce and travel with the lateral ligaments of the bladder into the internal iliac veins. The

lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...

drained from the bladder begins in a series of networks throughout the mucosal, muscular and serosal layers. 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 The external iliac lymph nodes are lymph nodes, from eight to ten in number, that lie along the external iliac vessels. They are arranged in three groups, one on the lateral, another on the medial, and a third on the anterior aspect of the vessel ...

Nerve supply

The bladder receives both sensory and motor supply from sympathetic and the

parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of ...

s. The motor supply from both sympathetic fibers, most of which arise from the superior and

inferior hypogastric plexus The inferior hypogastric plexus (pelvic plexus in some texts) is a network () of nerves that supplies the organs of the pelvic cavity. The inferior hypogastric plexus gives rise to the prostatic plexus in males and the uterovaginal plexus in female ...

es and nerves, and from parasympathetic fibers, which come from the

pelvic splanchnic nerves Pelvic splanchnic nerves or nervi erigentes are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the organs of the pelvic cavity. Structure The pelvic splanchnic nerves arise from t ...

. 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 A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

to S2-4. From here, sensation travels to the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

via the

dorsal columns Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

in the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

Microanatomy

When viewed under a microscope the bladder can be seen to have an inner lining (called

epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

), three layers of muscle fibres, and an outer

adventitia The adventitia () is the outer layer of fibrous connective tissue surrounding an organ. The outer layer of connective tissue that surrounds an artery, or vein – the tunica externa, is also called the ''tunica adventitia''. To some degree, its ...

. The inner wall of the bladder is called

urothelium Transitional epithelium also known as urothelium is a type of stratified epithelium. Transitional epithelium is a type of tissue that changes shape in response to stretching (stretchable epithelium). The transitional epithelium usually appears ...

, a type of

transitional epithelium Transitional epithelium also known as urothelium is a type of stratified epithelium. Transitional epithelium is a type of tissue that changes shape in response to stretching (stretchable epithelium). The transitional epithelium usually appears ...

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 A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

consisting of a surface

glycocalyx The glycocalyx, also known as the pericellular matrix, is a glycoprotein and glycolipid covering that surrounds the cell membranes of bacteria, epithelial cells, and other cells. In 1970, Martinez-Palomo discovered the cell coating in animal cells ...

that protects the cells beneath it from urine. The epithelium lies on a thin

basement membrane The basement membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between Epithelium, epithelial tissues including mesot ...

, and a

lamina propria The lamina propria is a thin layer of connective tissue that forms part of the moist linings known as mucous membranes or mucosae, which line various tubes in the body, such as the respiratory tract, the gastrointestinal tract, and the urogenita ...

. The mucosal lining also offers a urothelial barrier against the passing of infections. 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 detrusor muscle, which can be seen with the naked eye. The outside of the bladder is protected by a

serous membrane The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...

called

. File:Gray1141.png, Vertical section of bladder wall File:Urinary bladder.JPG, Layers of the urinary bladder wall and cross-section of the detrusor muscle File:2605 The Bladder.jpg, Anatomy of the male bladder, showing transitional epithelium and part of the wall in a histological cut-out

Development

In the developing

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

, at the hind end lies a

cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...

. This, over the fourth to the seventh week, divides into a

urogenital sinus The urogenital sinus is a part of the human body only present in the development of the urinary and reproductive organs. It is the ventral part of the cloaca, formed after the cloaca separates from the anal canal during the fourth to seventh we ...

and the beginnings of the

anal canal The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional segment ...

, with a wall forming between these two inpouchings called the

urorectal septum The urorectal septum is an invagination of the cloaca. It divides it into a dorsal part (the hindgut) and a ventral part (the urogenital sinus). It invaginates from cranial to caudal, formed from the endodermal cloaca, and fuses with the cloacal ...

. The urogenital sinus divides into three parts, with the upper and largest part becoming the bladder; the middle part becoming the

, and the lower part changes depending on the biological sex of the embryo. The human urinary bladder derives from the

, and it is initially continuous with the

allantois The allantois (plural ''allantoides'' or ''allantoises'') is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extraembryonic tissues). It helps the embryo ...

. The upper and lower parts of the bladder develop separately and join together around the middle part of

development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

. At this time the ureters move from the

mesonephric duct The mesonephric duct (also known as the Wolffian duct, archinephric duct, Leydig's duct or nephric duct) is a paired Organ (anatomy), organ that forms during the embryonic development of humans and other mammals and gives rise to male Sex organ, r ...

s to the trigone. In males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the

prostate The prostate is both an Male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, ...

, and separated from the

rectum The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...

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

by the

. In

infants An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...

and young children the urinary bladder is in the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

even when empty.

Function

Urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

, excreted by the

s, collects in the bladder because of drainage from two

s, before disposal by

(micturition). Urine leaves the bladder via the

, a single muscular tube ending in an opening called the

urinary meatus The urinary meatus, (, ) also known as the external urethral orifice, is the opening of the urethra. It is the point where urine exits the urethra in both sexes and where semen exits the urethra in males. The meatus has varying degrees of sensiti ...

, where it exits the body. Urination involves coordinated muscle changes involving a reflex based in the spine, with

higher Higher may refer to: Music * The Higher, a 2002–2012 American pop rock band Albums * ''Higher'' (Ala Boratyn album) or the title song, 2007 * ''Higher'' (Ezio album) or the title song, 2000 * ''Higher'' (Harem Scarem album) or the title song ...

inputs from the brain. During urination, the detrusor muscle contracts, and the external urinary sphincter and muscles of the

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...

relax, allowing urine to pass through the

and out of the body. The urge to pass urine stems from

stretch receptor Stretch receptors are mechanoreceptors responsive to distention of various organs and muscles, and are neurologically linked to the Medulla oblongata, medulla in the brain stem via Afferent nerve fiber, afferent nerve fibers. Examples include stre ...

s that activate when between 300 - 400 mL urine is held within the 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 The Pontine micturition center (PMC, also known as Barrington's nucleus) is a collection of neuronal cell bodies located in the rostral pons in the brainstem involved in the supraspinal regulation of micturition. When activated, the PMC relaxes th ...

in the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...

Stretch receptor Stretch receptors are mechanoreceptors responsive to distention of various organs and muscles, and are neurologically linked to the Medulla oblongata, medulla in the brain stem via Afferent nerve fiber, afferent nerve fibers. Examples include stre ...

s in the bladder signal the

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...

nervous system to stimulate the

muscarinic receptor Muscarinic acetylcholine receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled receptor, G protein-coupled receptor complexes in the cell membranes of certain neurons and other Cell (biology), cells. They play several r ...

s in the detrusor to contract the muscle when the bladder is distended. This encourages the bladder to expel urine through the urethra. The main receptor activated is the

M3 receptor The muscarinic acetylcholine receptor, also known as cholinergic/acetylcholine receptor M3, or the muscarinic 3, is a muscarinic acetylcholine receptor encoded by the human gene CHRM3. The M3 muscarinic receptors are located at many places in t ...

, although M2 receptors are also involved and whilst outnumbering the M3 receptors they are not so responsive. The main relaxant pathway is via the

adenylyl cyclase Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction: :A ...

cAMP Camp may refer to: Outdoor accommodation and recreation * Campsite or campground, a recreational outdoor sleeping and eating site * a temporary settlement for nomads * Camp, a term used in New England, Northern Ontario and New Brunswick to descri ...

pathway, activated via the β3 adrenergic receptors. The β2 adrenergic receptors are also present in the detrusor and even outnumber β3 receptors, but they do not have as important an effect in relaxing the detrusor smooth muscle.

Clinical significance

Inflammation and infection

Cystitis A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

refers to infection or inflammation of the bladder. It commonly occurs as part of a

urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

. In adults, it is more common in women than men, owing to a shorter

. It is common in males during childhood, and in older men where an enlarged prostate may cause urinary retention. Other risk factors include other causes of blockage or narrowing, such as

prostate cancer Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that sur ...

or the presence of vesico-ureteric reflux; the presence of outside structures in the urinary tract, such as

urinary catheter In urinary catheterization a latex, polyurethane, or silicone tube known as a urinary catheter is inserted into the bladder through the urethra to allow urine to drain from the bladder for collection. It may also be used to inject liquids used ...

s; and neurologic problems that make passing urine difficult. Infections that involve the bladder can cause pain in the lower abdomen (above the

, so called "suprapubic" pain), particularly before and after passing urine, and a desire to pass urine frequently and with little warning (

urinary urgency Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

). Infections are usually due to

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, of which the most common is

E coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

. When a urinary tract infection or cystitis is suspected, a

medical practitioner A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...

may request a

urine sample A urine test is any medical test performed on a urine specimen. The analysis of urine is a valuable diagnostic tool because its composition reflects the functioning of many body systems, particularly the kidneys and urinary system, and specimens a ...

. A dipstick placed in the urine may be used to see if the urine has

white blood cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

, or the presence of

nitrates Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insoluble ...

which may indicate an infection. The urine specimen may be also sent for microbial culture and sensitivity to assess if a particular bacteria grows in the urine, and identify its antibiotic sensitivities. Sometimes, additional investigations may be requested. These might include testing the function of the kidneys by assessing

electrolytes An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon di ...

and

creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an import ...

; investigating for blockages or narrowing of the renal tract with a

ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...

, and testing for an enlarged prostate with a

digital rectal examination Digital rectal examination (DRE; la, palpatio per anum, PPA) is an internal examination of the rectum, performed by a healthcare provider. Prior to a 2018 report from the U.S. Preventive Services Task Force, the DRE was a common and "dreaded" co ...

. Urinary tract infections or cystitis are treated with

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...

s, many of which are consumed by mouth. Serious infections may require treatment with

intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

antibiotics.

Interstitial cystitis Interstitial cystitis (IC), a type of bladder pain syndrome (BPS), is chronic pain in the bladder and pelvic floor of unknown cause. It is the urologic chronic pelvic pain syndrome of women. Symptoms include feeling the need to urinate right awa ...

refers to a condition in which the bladder is infected due to a cause that is not bacteria.

Incontinence and retention

Frequent urination can be due to excessive urine production, small bladder capacity, irritability or incomplete emptying. Males with an

enlarged prostate Benign prostatic hyperplasia (BPH), also called prostate enlargement, is a noncancerous increase in size of the prostate gland. Symptoms may include frequent urination, trouble starting to urinate, weak stream, inability to urinate, or loss o ...

urinate more frequently. One definition of an

overactive bladder Overactive bladder (OAB) is a condition where there is a frequent feeling of needing to urinate to a degree that it negatively affects a person's life. The frequent need to urinate may occur during the day, at night, or both. If there is loss ...

is when a person urinates more than eight times per day. An overactive bladder can often cause

urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. It has been identified as an important issue in geria ...

. Though both urinary frequency and volumes have been shown to have a circadian rhythm, meaning day and night cycles, it is not entirely clear how these are disturbed in the overactive bladder.

Urodynamic testing Urodynamic testing or urodynamics is a study that assesses how the bladder and urethra are performing their job of storing and releasing urine. Urodynamic tests can help explain symptoms such as: * incontinence * frequent urination * sudden, stro ...

can help to explain the symptoms. An

underactive bladder Underactive bladder syndrome (UAB) describes symptoms of difficulty with bladder emptying, such as hesitancy to start the stream, a poor or intermittent stream, or sensations of incomplete bladder emptying. The physical finding of detrusor activ ...

is the condition where there is a difficulty in passing urine and is the main symptom of a

neurogenic bladder Neurogenic bladder dysfunction, or neurogenic bladder, refers to urinary bladder problems due to disease or injury of the central nervous system or peripheral nerves involved in the control of urination. There are multiple types of neurogenic bladde ...

. Frequent urination at night may indicate the presence of

bladder stone A bladder stone is a stone found in the urinary bladder. Signs and symptoms Bladder stones are small mineral deposits that can form in the bladder. In most cases bladder stones develop when the urine becomes very concentrated or when one is d ...

s. Disorders of or related to the bladder include: *

Bladder exstrophy Bladder exstrophy is a congenital anomaly that exists along the spectrum of the exstrophy-epispadias complex, and most notably involves protrusion of the urinary bladder through a defect in the abdominal wall. Its presentation is variable, often ...

Bladder sphincter dyssynergia Bladder sphincter dyssynergia (also known as detrusor sphincter dyssynergia (DSD) (the ICS standard terminology agreed 1998) and neurogenic detrusor overactivity (NDO)) is a consequence of a neurological pathology such as spinal injury or multip ...

, a condition in which the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles *

Paruresis Paruresis, also known as shy bladder syndrome, is a type of phobia in which a person is unable to urinate in the real or imaginary presence of others, such as in a public restroom. The analogous condition that affects bowel movement is called ...

Trigonitis Trigonitis is a condition of inflammation of the trigone region of the bladder. It is more common in women. The cause of trigonitis is not known, and there is no solid treatment. Electrocautery is sometimes used, but is generally unreliable as a ...

Underactive bladder Underactive bladder syndrome (UAB) describes symptoms of difficulty with bladder emptying, such as hesitancy to start the stream, a poor or intermittent stream, or sensations of incomplete bladder emptying. The physical finding of detrusor activ ...

, a condition with its main symptom being

urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladd ...

. 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 Bladder augmentation is a surgical alteration of the urinary bladder. It involves removing strips of tissue from the intestinal tract and adding this to the tissue of the bladder. This has two intended results: increased bladder volume; and ...

. An obstruction of the bladder neck may be severe enough to warrant surgery.

Cancer

Cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

of the bladder is known as

bladder cancer Bladder cancer is any of several types of cancer arising from the tissues of the urinary bladder. Symptoms include blood in the urine, pain with urination, and low back pain. It is caused when epithelial cells that line the bladder become mali ...

. It is usually due to cancer of the

, the cells that line the surface of the bladder. Bladder cancer is more common after the age of 40, and more common in men than women; other risk factors include

smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...

and exposure to

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

s such as

aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aromatic ring attached to an amine. It is a broad class of compounds that encompasses anilines, but also many more complex aromatic rings and many amine substituents ...

s and

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

. When cancer is present, the most common symptom in an affected person is

blood in the urine Hematuria or haematuria is defined as the presence of blood or red blood cells in the urine. “Gross hematuria” occurs when urine appears red, brown, or tea-colored due to the presence of blood. Hematuria may also be subtle and only detectable w ...

; a physical

medical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the patient ...

may be otherwise normal, except in late disease. Bladder cancer is most often due to cancer of the cells lining the ureter, called

transitional cell carcinoma Transitional cell carcinoma, also called urothelial carcinoma, is a type of cancer that typically occurs in the urinary system. It is the most common type of bladder cancer and cancer of the ureter, urethra, and urachus. It accounts for 95% of ...

, although it can more rarely occur as a

squamous cell carcinoma Squamous-cell carcinomas (SCCs), also known as epidermoid carcinomas, comprise a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...

if the type of cells lining the urethra have changed due to chronic inflammation, such as due to stones or

schistosomiasis Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody s ...

. Investigations performed usually include collecting a sample of urine for an inspection for malignant cells under a microscope, called

cytology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...

, as well as

medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...

by a

CT urogram A computed tomography urography (CT urography or CT urogram) is a computed tomography scan that examines the urinary tract after contrast dye is injected into a vein. In a CT urogram, the contrast agent is through a cannula into a vein, allo ...

. If a concerning lesion is seen, a flexible camera may be inserted into the bladder, called

cystoscopy Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscope ...

, in order to view the lesion and take a

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

, and a CT scan will be performed of other body parts (a CT scan of the chest, abdomen and pelvis) to look for additional lesions. Treatment depends on the cancer's

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

. Cancer present only in the bladder may be removed surgically via

; an injection of the

chemotherapeutic Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothera ...

mitomycin C Mitomycin C is a mitomycin that is used as a chemotherapeutic agent by virtue of its antitumour activity. Medical uses It is given intravenously to treat upper gastro-intestinal cancers (e.g. esophageal carcinoma), anal cancers, and breast c ...

may be performed at the same time. Cancers that are high grade may be treated with an injection of the

BCG vaccine Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is named after its inventors Albert Calmette and Camille Guérin. In countries where tuberculosis or leprosy is common, one dose is recommended ...

into the bladder wall, and may require surgical removal if it does not resolve. Cancer that is invading through the bladder wall may be managed by complete surgical removal of the bladder (

radical cystectomy Cystectomy is a medical term for surgery, surgical removal of all or part of the urinary bladder. It may also be rarely used to refer to the removal of a cyst. The most common condition warranting removal of the urinary bladder is bladder cancer. ...

), with the ureters diverted into a segment of part of

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine ma ...

connected to a

stoma bag An ostomy pouching system is a prosthetic medical device that provides a means for the collection of waste from a surgically diverted biological system ( colon, ileum, bladder) and the creation of a stoma. Pouching systems are most commonly asso ...

on the skin. Prognosis can vary markedly depending on the cancer's stage and grade, with a better prognosis associated with tumours found only in the bladder, that are low grade, that don't invade through the bladder wall, and that is in visual appearance.

Investigation

A number of investigations are used to examine the bladder. The investigations that are ordered will depend on the taking of a

medical history The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is information gained by a physician by asking specific questions, either to the patient or to other peo ...

and an examination. The examination may involve a

feeling in the suprapubic area for tenderness or fullness that might indicate an inflamed or full bladder. Blood tests may be ordered that may indicate inflammation; for example a

full blood count A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cells and plat ...

may demonstrate elevated

white blood cell White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...

s, or a

C-reactive protein C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin-6 ...

may be elevated in an infection. Some forms of

exist to visualise the bladder. A

bladder ultrasound The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

may be conducted to view how much urine is within the bladder, indicating

. A

urinary tract ultrasound Ultrasound of the urinary tract involves the use of an ultrasound probe to image parts of the urinary tract. The urinary tract is the path that urine follows after it is formed within the kidneys, and involves a left and right ureter, the bladder, ...

, conducted by a more trained operator, may be conducted to view whether there are stones, tumours or sites of obstruction within the bladder and urinary tract. A CT scan may also be ordered. A flexible internal camera, called a

cystoscope Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscope ...

, can be inserted to view the internal appearance of the bladder and take a

if required.

can help to explain the symptoms.

Other animals

Mammals

All mammals have a urinary bladder. This structure begins as an

embryonic cloaca The cloaca is a structure in the development of the urinary and reproductive organs. The hind-gut is at first prolonged backward into the body-stalk as the tube of the allantois; but, with the growth and flexure of the tail-end of the embryo, ...

. 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 The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal Endemic (ecology), endemic to Eastern states of Australia, eastern Australia, including Tasmania. The platypu ...

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

cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...

s (whales and dolphins) is proportionally smaller than that of land-dwelling mammals.

Reptiles

In all reptiles, the urinogenital ducts and the

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...

both empty into an organ called a

. 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 Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recogn ...

, the

legless lizard Legless lizard may refer to any of several groups of lizards that have independently lost limbs or reduced them to the point of being of no use in locomotion.Pough ''et al.'' 1992. Herpetology: Third Edition. Pearson Prentice Hall:Pearson Education ...

s. It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders.

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

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. 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 Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration o ...

. 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.

Amphibians

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 ''Xenopus'' () (Gk., ξενος, ''xenos''=strange, πους, ''pous''=foot, commonly known as the clawed frog) is a genus of highly aquatic frogs native to sub-Saharan Africa. Twenty species are currently described within it. The two best-known ...

'' 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.

Fish

The gills of most

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...

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

s 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

loach Loaches are fish of the superfamily Cobitoidea. They are freshwater, benthic (bottom-dwelling) fish found in rivers and creeks throughout Eurasia and northern Africa. Loaches are among the most diverse groups of fish; the 1249 known species of ...

es,

pilchard "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the ...

s, and

herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...

s 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

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

s and behind the

. The urinary bladders of fish and

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

s are thought to be analogous while the former's swim-bladders and latter's

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

s are considered homologous.

Birds

In nearly all bird species, there is no urinary bladder per se. Although all birds have kidneys, the

ureters The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epith ...

open directly into a

which serves as a reservoir for urine, fecal matter, and eggs.

Crustaceans

Unlike the urinary bladder of vertebrates, the urinary bladder of

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s 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

References

;Books * *

External links

* – "Mammal, bladder (LM, Medium)"
Bladder
() – An open-access journal on bladder biology and diseases. {{Use dmy dates, date=April 2017 Pelvis Organs (anatomy) Urinary system