Urinary system
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223517330
2008-07-04T12:14:55Z
Da monster under your bed
2040962
Reverted edits by [[Special:Contributions/202.175.101.50|202.175.101.50]] to last version by 160.39.51.25 (using [[WP:HG|Huggle]])
The '''urinary system''' (also called [[excretory system]] or the genitourinary system (GUS)) is the [[organ system]] that produces, stores, and eliminates [[urine]]. In humans it includes two [[kidney]]s, two [[ureter]]s, the [[urinary bladder|bladder]], and the [[urethra]]. The analogous organ in invertebrates is the [[nephridium]].
==Physiology==
{{Main|Kidney}}
Human beings typically have two kidneys. The [[kidney]]s are [[Kidney bean|bean]]-shaped organs, which lie in the [[abdomen]], rump or [[retroperitoneal]] to the organs of digestion, around or just below the ribcage and close to the [[lumbar spine]]. The organ is about the size of a chocolate bar and is surrounded by what is called peri-nephric fat, and situated on the superior pole of each kidney is an [[adrenal gland]]. The kidneys receive their blood supply of 1.25 L/min (25% of the [[cardiac output]]) from the renal arteries which are fed by the [[Abdominal aorta]]. This is important because the kidneys' main role is to filter [[water soluble]] waste products from the blood. The other attachment of the kidneys are at their functional endpoints the [[ureters]], which lies more [[Anatomical terms of location|medial]] and runs down to the [[Trigone of urinary bladder|trigone]] of the [[Urinary bladder|bladder]].
Functionally the kidney performs a [[Renal physiology|number of tasks]]. In its role in the urinary system it concentrates urine, plays a crucial role in regulating [[electrolyte]]s, and maintains [[acid-base homeostasis]]. The kidney excretes and re-absorbs [[electrolyte]]s (e.g. [[sodium]], [[potassium]] and [[calcium]]) under the influence of local and systemic [[hormones]]. [[pH]] balance is regulated by the excretion of [[Titratable acid|bound acids]] and [[ammonium]] ions. In addition, they remove [[urea]], a nitrogenous waste product from the [[metabolism]] of proteins from [[amino acid]]s. The end point is a [[Osmole (unit)|hyperosmolar]] solution carrying waste for storage in the bladder prior to [[urination]].
[[Human]]s produce about 1.5 [[liter]]s of urine over 24 hours, although this amount may vary according to circumstances. Because the rate of filtration at the kidney is [[Proportionality (mathematics)|proportional]] to the [[glomerular filtration rate]], which is in turn related to the blood flow through the kidney, changes in body fluid status can affect kidney function. Hormones exogenous and endogenous to the kidney alter the amount of blood flowing through the [[glomerulus]]. Some [[medication]]s interfere directly or indirectly with urine production. [[Diuretic]]s achieve this by altering the amount of absorbed or excreted electrolytes or [[Osmole (unit)|osmalites]], which causes a [[diuresis]].
===Bladder===
{{Main|Urinary bladder|l1=Bladder}}
In [[human]]s and other related organisms, the [[urinary bladder]] is a hollow muscular organ shaped like a balloon, located in the anterior pelvis. The bladder stores urine. the maximum that it can hold is one litre. It swells into a round shape when it is full and gets smaller when empty. In the absence of bladder disease, it can hold up to 300 ml of urine comfortably for two to five hours. The epithelial tissue associated with the bladder is called [[transitional epithelium]]. Normally the bladder is [[sterile]].
[[Sphincter]]s (circular muscles) regulate the flow of urine from the bladder. The bladder itself has a muscular layer ([[detrusor muscle]]) that, when contracted, increases pressure on the bladder and creates urinary flow.
[[Urination]] is a conscious process, generally initiated by stretch receptors in the bladder wall which signal to the brain that the bladder is full. This is felt as an urge to urinate. When urination is initiated, the sphincter relaxes and the detrusor muscle contracts, producing urinary flow.
===Urethra===
{{Main|Urethra}}
The endpoint of the urinary system is the urethra. Typically the urethra in humans is colonised by [[commensal bacteria]] below the external urethral sphincter. The urethra emerges from the end of the [[penis]] in males and between the [[clitoris]] and the [[vagina]] in females.
==Role in disease==
Kidney diseases are normally investigated and treated by [[nephrologist]]s, while the specialty of [[urology]] deals with problems in the other organs. [[Gynecology|Gynecologists]] may deal with problems of incontinence in women.
Diseases of other bodily systems also have a direct effect on urogenital function. For instance it has been shown that [[protein]][[ released by the kidneys in [[diabetes mellitus]] sensitises the kidney to the damaging effects of [[hypertension]]
<ref>Baba T, Murabayashi S, Tomiyama T, Takebe K; Uncontrolled hypertension is associated with a rapid progression of nephropathy in type 2 diabetic patients with proteinuria and preserved renal function. Tohoku J Exp Med 1990 Aug;161(4):311-8 PMID 2256104 </ref>.
[[Diabetes]] also can have a direct effect in [[micturition]] due to [[peripheral neuropathy|peripheral neuropathies]] which occur in some individuals with poorly controlled diabetics.
===Kidney disease===
[[Renal failure]] is defined by functional impairment of the kidney. Renal failure can be [[acute renal failure|acute]] or [[chronic renal failure|chronic]], and can be further broken down into categories of pre-renal, intrinsic renal and post-renal.
Pre-renal failure refers to impairment of supply of blood to the functional nephrons including [[renal artery stenosis]]. Intrinsic renal diseases are the classic diseases of the kidney including drug toxicity and [[nephritis]]. Post-renal failure is outlet obstruction after the kidney, such as a [[kidney Stone|renal stone]] or [[urinary retention|prostatic bladder outlet obstruction]].
[[Renal failure]] may require [[medication]], dietary and lifestyle modification and [[dialysis]].
Primary renal cell carcinomas as well as metastatic cancers can affect the [[kidney]].
===Non-renal urinary tract disease===
The causes of diseases of the body are common to the urinary tract. Structural and or traumatic change can lead to [[hemorrhage]], functional blockage or [[inflammation]]. Colonisation by [[bacteria]], [[protozoa]] or [[fungi]] can cause infection. Uncontrolled cell growth can cause [[neoplasia]].
For example:
*[[Urinary tract infection]]s (UTIs), [[interstitial cystitis]]
*[[Urinary incontinence|incontinence]] (involuntary loss of urine), [[benign prostatic hyperplasia]] (where the prostate overgrows), [[prostatitis]] (inflammation of the prostate).
* Transitional cell carcinoma ([[bladder cancer]]), [[renal cell carcinoma]] (kidney cancer), and [[prostate cancer]] are examples of [[neoplasm]]s affecting the urinary system.
The term "uropathy" refers to a disease of the urinary tract, while "[[nephropathy]]" refers to a disease of the kidney.
==Testing==
[[Biochemical]] blood tests determine the amount of typical markers of renal function in the blood serum, for instance serum [[urea]] and serum [[creatinine]]. Biochemistry can also be used to determine serum electrolytes. Special biochemical tests ([[arterial blood gas]]) can determine the amount of dissolved gases in the blood, indicating if pH imbalances are acute or chronic.
[[Urinalysis]] is a test that studies [[urine]] for abnormal substances such as protein or signs of infection.
*A Full Ward Test, also known as [[dipstick]] urinalysis, involves the dipping of a biochemically active test strip into the urine specimen to determine levels of tell-tale chemicals in the urine.
*Urinalysis can also involve MC&S [[microscopy]] , [[microbiological culture|culture]] and [[antibiotic sensitivity|sensitivity]]
[[Urodynamics|Urodynamic tests]] evaluate the storage of urine in the bladder and the flow of urine from the bladder through the urethra. It may be performed in cases of incontinence or neurological problems affecting the urinary tract.
[[Medical ultrasonography|Ultrasound]] is commonly performed to investigate problems of the kidney and/or urinary tract.
[[Radiology]]:
*[[KUB]] is plain radiography of the urinary system, e.g. to identify [[kidney stone]]s.
*An [[intravenous pyelogram]] studies the shape of the urinary system.
*[[CAT scan]]s and [[MRI]] can also be useful in localising urinary tract pathology.
* A voiding cystogram is a functional study where contrast "dye" is injected through a catheter into the bladder. Under x-ray the radiologist asks the patient to void (usually young children) and will watch the contrast exiting the body on the x-ray monitor. This examines the child's bladder and lower urinary tract. Typically looking for [[vesicoureteral reflux]], involving urine backflow up into the kidneys.
== See also ==
*[[Urothelium]]
*[[Major systems of the human body]]
==References==
{{reflist}}
{{organ_systems}}
{{Renal physiology}}
{{Nephrology}}
{{Development of urinary and reproductive systems}}
[[Category:Urinary system| ]]
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[[fr:Système urinaire]]
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