Urinary bladder
Encyclopedia
The urinary bladder is the organ that collects urine
excreted by the kidney
s before disposal by urination
. A hollow muscular
, and distensible (or elastic) organ, the bladder sits on the pelvic floor
. Urine enters the bladder via the ureter
s and exits via the urethra
.
Bladder
s occur throughout much of the animal kingdom
, but are very diverse in form and in some cases are not homologous
with the urinary bladder in humans.
The human urinary bladder is derived in embryo from the urogenital sinus
and, it is initially continuous with the allantois
. 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 rectovesical excavation
. 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 vesicouterine excavation
. In infants and young children, the urinary bladder is in the abdomen
even when empty.
fibers arranged in spiral, longitudinal, and circular bundles
. When the bladder is stretched, this signals the parasympathetic nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra.
For the urine to exit the bladder, both the autonomic
ally controlled internal sphincter
and the voluntarily
controlled external sphincter must be opened. Problems with these muscles can lead to incontinence
.
The urinary bladder usually holds 300-350 ml of urine. As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure.
The urge to urinate usually starts when the bladder reaches around 25% of its working volume. At this stage it is easy for the subject, if desired, to resist the urge to urinate. As the bladder continues to fill, the desire to urinate becomes stronger and harder to ignore. Eventually, the bladder will fill to the point where the urge to urinate becomes overwhelming, and the subject will no longer be able to ignore it. If the amount of urine reaches 100% of the urinary bladder's capacity, the voluntary sphincter becomes involuntary, and the urine will be ejected instantly.
Since the urinary bladder has a transitional epithelium, it does not produce mucus.
The fundus of the urinary bladder is the base of the bladder, formed by the posterior wall. It is lymphatically drained by the external iliac lymph nodes. The peritoneum
lies superior to the fundus.
is when a person urinates more than eight times per day, though there can be other causes of urination frequency.
Sensation from the bladder is transmitted to the central nervous system (CNS) via general visceral afferent fibers
(GVA). GVA fibers on the superior surface follow the course of the sympathetic efferent nerves back to the CNS, while GVA fibers on the inferior portion of the bladder follow the course of the parasympathetic efferents.
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
excreted by the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s before disposal by urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...
. A hollow muscular
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
, and distensible (or elastic) organ, the bladder sits on the pelvic floor
Pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...
. Urine enters the bladder via the ureter
Ureter
In human anatomy, the ureters are muscular tubes that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually long and ~3-4 mm in diameter....
s and exits via the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
.
Bladder
Bladder
Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...
s occur throughout much of the animal kingdom
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
, but are very diverse in form and in some cases are not homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
with the urinary bladder in humans.
The human urinary bladder is derived in embryo from the urogenital sinus
Urogenital sinus
The definitive urogenital sinus is a part of the human body only present in the development of the urinary and reproductive organs...
and, it is initially continuous with the allantois
Allantois
Allantois is a part of a developing animal conceptus . It helps the embryo exchange gases and handle liquid waste....
. In males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
, and separated from the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
by the rectovesical excavation
Rectovesical excavation
Between the rectum and the bladder the peritoneal cavity forms, in the male, a pouch, the rectovesical excavation , the bottom of which is slightly below the level of the upper ends of the vesiculae seminales—i. e., about 7.5 cm. from the orifice of the anus...
. 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
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
by the vesicouterine excavation
Vesicouterine excavation
In human female anatomy, the vesicouterine excavation is a second, but shallower, pouch formed from the peritoneum over the uterus and bladder, continued over the intestinal surface and fundus of the uterus onto its vesical surface, which it covers as far as the junction of the body and cervix...
. In infants and young children, the urinary bladder is in the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
even when empty.
Detrusor muscle
The detrusor muscle is a layer of the urinary bladder wall made of smooth muscleSmooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
fibers arranged in spiral, longitudinal, and circular bundles
Fiber bundle
In mathematics, and particularly topology, a fiber bundle is intuitively a space which locally "looks" like a certain product space, but globally may have a different topological structure...
. When the bladder is stretched, this signals the parasympathetic nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra.
For the urine to exit the bladder, both the autonomic
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
ally controlled internal sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...
and the voluntarily
Somatic
The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...
controlled external sphincter must be opened. Problems with these muscles can lead to incontinence
Urinary incontinence
Urinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
.
The urinary bladder usually holds 300-350 ml of urine. As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure.
The urge to urinate usually starts when the bladder reaches around 25% of its working volume. At this stage it is easy for the subject, if desired, to resist the urge to urinate. As the bladder continues to fill, the desire to urinate becomes stronger and harder to ignore. Eventually, the bladder will fill to the point where the urge to urinate becomes overwhelming, and the subject will no longer be able to ignore it. If the amount of urine reaches 100% of the urinary bladder's capacity, the voluntary sphincter becomes involuntary, and the urine will be ejected instantly.
Since the urinary bladder has a transitional epithelium, it does not produce mucus.
Fundus
The fundus of the urinary bladder is the base of the bladder, formed by the posterior wall. It is lymphatically drained by the external iliac lymph nodes. The peritoneum
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
lies superior to the fundus.
Urination frequency
Urination frequency refers to the number of times someone urinates. Males with an enlarged prostate urinate more frequently. One definition of Overactive bladderOveractive bladder
Overactive bladder is a urological condition defined by a set of symptoms: urgency, with or without urge incontinence, usually with frequency and nocturia. Frequency is usually defined as urinating more than 8 times a day. The International Continence Society is responsible for this definition...
is when a person urinates more than eight times per day, though there can be other causes of urination frequency.
Innervation
The bladder receives motor innervation from both sympathetic fibers, most of which arise from the hypogastric plexuses and nerves, and parasympathetic fibers, which come from the pelvic splanchnic nerves and the inferior hypogastric plexus.Sensation from the bladder is transmitted to the central nervous system (CNS) via general visceral afferent fibers
General visceral afferent fibers
The general visceral afferent fibers conduct sensory impulses from the viscera, glands, and blood vessels to the central nervous system. They are considered to be part of the autonomic nervous system...
(GVA). GVA fibers on the superior surface follow the course of the sympathetic efferent nerves back to the CNS, while GVA fibers on the inferior portion of the bladder follow the course of the parasympathetic efferents.
Disorders
Disorders of or related to the bladder include:- Bladder cancerBladder cancerBladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
- Bladder exstrophyBladder exstrophyBladder exstrophy is a congenital anomality in which part of the urinary bladder is present outside the body. It is rare, occurring once every 10,000 to 50,000 live births with a 2:1 male:female ratio. The diagnosis involves a spectrum of anomalies of the lower abdominal wall, bladder, anterior...
- Bladder infection
- Bladder spasmBladder spasmA bladder spasm is a contraction of the bladder which generates an urge to urinate, sometimes accompanied by extreme pain. Incontinence may occur if the bladder spasm continues, as the contraction will force urine out...
- Bladder sphincter dyssynergiaBladder sphincter dyssynergiaBladder sphincter dyssynergia is a consequence of a neurological pathology such as spinal injury or multiple sclerosis that disrupts central nervous system regulation of the micturition reflex resulting in dyscoordination of...
, a condition in which the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles - Bladder stones
- CystitisCystitisCystitis is a term that refers to urinary bladder inflammation that results from any one of a number of distinct syndromes. It is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection.-Signs and symptoms:...
- HematuriaHematuriaIn medicine, hematuria, or haematuria, is the presence of red blood cells in the urine. It may be idiopathic and/or benign, or it can be a sign that there is a kidney stone or a tumor in the urinary tract , ranging from trivial to lethal...
, or presence of blood in the urine, is a reason to seek medical attention without delay, as it is a symptom of bladder cancer as well as bladder and kidney stoneKidney stoneA kidney stone, also known as a renal calculus is a solid concretion or crystal aggregation formed in the kidneys from dietary minerals in the urine...
s - Interstitial CystitisInterstitial cystitisInterstitial cystitis or bladder pain syndrome is a chronic, oftentimes severely debilitating disease of the urinary bladder...
- Overactive bladderOveractive bladderOveractive bladder is a urological condition defined by a set of symptoms: urgency, with or without urge incontinence, usually with frequency and nocturia. Frequency is usually defined as urinating more than 8 times a day. The International Continence Society is responsible for this definition...
, a condition that affects a large number of people - Urinary incontinenceUrinary incontinenceUrinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
- Urinary retentionUrinary retentionUrinary retention, also known as ischuria, is a lack of ability to urinate. It is a common complication of benign prostatic hyperplasia , although it can also be caused by nerve dysfunction, constipation, infection, or medications...
See also
- Artificial urinary bladderArtificial urinary bladderAn artificial urinary bladder is an artificial organ to replace a urinary bladder.On April 4, 2006, it was announced that a team of biologists at the Wake Forest University School of Medicine, led by Professor Anthony Atala, had created the world's first lab-grown organ, a bladder, and transplanted...
- Bladder (disambiguation)
- Bladder augmentationBladder augmentationBladder 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...
- Neurogenic bladderNeurogenic bladderNeurogenic bladder refers to dysfunction of the urinary bladder due to disease of the central nervous system or peripheral nerves involved in the control of micturition .-Causes:...
- UreteroceleUreteroceleA ureterocele is a congenital abnormality found in the urinary bladder. In this condition called ureteroceles, the distal ureter balloons at its opening into the bladder, forming a sac-like pouch. It is most often associated with a duplicated collection system, where two ureters drain their...
- Urodynamics
- Uvula of urinary bladderUvula of urinary bladderThe mucous membrane immediately behind the internal urethral orifice presents a slight elevation, the uvula of urinary bladder, caused by the middle lobe of the prostate....
- Vesicouretic refluxVesicouretic refluxVesicouretic reflux is a condition in which normal compression of the bladder during urination results in an abnormal backflow of urine into the kidneys. It is the second most common renal disease in children. Over a period of weeks, months or years, this leads to kidney infection, permanent...