In anatomy, the urinary bladder is the organ that collects urine excreted by the kidneys prior to disposal by urination. A hollow [1] muscular, and distensible (or elastic) organ, the bladder 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 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. 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.[2]
Embryologically, the bladder is derived 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. 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.[2]
Detrusor muscleThe detrusor muscle is a layer of the urinary bladder wall made of smooth muscle 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 autonomically controlled internal sphincter and the voluntarily controlled external sphincter must be opened. Problems with these muscles can lead to incontinence. 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, although it is possible to "hold yourself" in order to prevent urination.[clarification needed]
The urinary bladder usually holds 400–620 mL of urine[citation needed], but it can hold twice this without rupturing[citation needed] if, for example, the outflow is obstructed.
The desire to urinate usually starts when the bladder reaches around 25%[3] of its working volume. If the subject is distracted the desire can fade and return with more urgency as the bladder continues to fill.
Since the urinary bladder has a transitional epithelium, compared to the intestine mucosa, the urinary bladder does not produce mucus.[4]
[edit]FundusThe 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.
[edit]DisordersDisorders of or related to the bladder include:
For the urine to exit the bladder, both the autonomically controlled internal sphincter and the voluntarily controlled external sphincter must be opened. Problems with these muscles can lead to incontinence. 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, although it is possible to "hold yourself" in order to prevent urination.[clarification needed]
The urinary bladder usually holds 400–620 mL of urine[citation needed], but it can hold twice this without rupturing[citation needed] if, for example, the outflow is obstructed.
The desire to urinate usually starts when the bladder reaches around 25%[3] of its working volume. If the subject is distracted the desire can fade and return with more urgency as the bladder continues to fill.
Since the urinary bladder has a transitional epithelium, compared to the intestine mucosa, the urinary bladder does not produce mucus.[4]
[edit]FundusThe 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.
[edit]DisordersDisorders of or related to the bladder include:
- Overactive bladder, a condition which affects a large number of people.
- Bladder cancer
- Bladder infection
- Bladder spasm
- Bladder sphincter dyssynergia, a condition in which the sufferer cannot coordinate relaxation of the urethra sphincter with the contraction of the bladder muscles
- Bladder stones
- Cystitis
- Interstitial Cystitis
- Hematuria, 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 stones.
- Urinary incontinence
- Bladder exstrophy
- Urinary retention
v • d • eAnatomy: urinary system (TA A08, GA 11.1215)AbdomenKidneysLayersRenal fascia • Renal capsule • Renal cortex (Renal column) •Renal medulla (Renal sinus, Renal pyramids, medullary interstitium) • Renal lobe • Cortical lobule • Medullary ray • NephronAfferent circulationRenal artery → Segmental arteries → Interlobar arteries → Arcuate arteries → Interlobular arteries → Afferent arterioles → Renal corpuscle (Glomerulus, Bowman's capsule)Renal tubuleProximal tubule → Loop of Henle (Descending, Thin ascending, Thick ascending) →Distal convoluted tubule → Connecting tubule → Collecting ducts aka Duct of Belini → Renal papilla → Minor calyx → Major calyx → Renal pelvis → UreterEfferent circulationGlomerulus → Efferent arterioles → Peritubular capillaries / Vasa recta → Arcuate vein →Interlobar veins → Renal veinJuxtaglomerular apparatusMacula densa • Juxtaglomerular cells • Mesangium/Extraglomerular mesangial cellFiltrationGlomerular basement membrane • Podocyte • Filtration slits • Mesangium/Intraglomerular mesangial cell • Tubular fluidUretersOrifice of ureterPelvisBladderUvula • Trigone • Detrusor • Apex • NeckUrethraUrethral sphincters (External sphincter muscle of male urethra, External sphincter muscle of female urethra, Internal sphincter muscle of urethra)urinary system navs: anat/physio/dev, noncongen/acid+base/congen/neoplasia, symptoms+signs/eponymous, proc
Categories: Pelvis | Organs | Urology | Urinary system
Categories: Pelvis | Organs | Urology | Urinary system
