Editing Human body (section)

==== Urinary system ====
{{Main|Urinary system}}
[[File:Urinary System (Female).png|left|thumb|Female [[urinary system]]]]
The [[urinary system]] consists of the two [[kidney]]s, two [[ureter]]s, [[bladder]], and [[urethra]]. It removes<!--excretion--> waste materials from the blood through urine, which carries a variety of waste molecules and excess [[ion]]s and water out of the body.

First, the [[kidney]]s filter the blood through their respective [[nephron]]s, removing [[Metabolic waste|waste products]] like [[urea]], [[creatinine]] and maintaining the [[Electrolyte imbalance|proper balance]] of [[electrolyte]]s and turning the waste products into [[urine]] by combining them with water from the blood.<ref>{{Cite web|title=The Kidneys – a Basic Guide|url=https://www.nhs.uk/Livewell/Kidneyhealth/Documents/kidney%20guide.pdf|url-status=live|archive-url=https://web.archive.org/web/20210109023755/https://www.nhs.uk/Livewell/Kidneyhealth/Documents/kidney%20guide.pdf|archive-date=January 9, 2021|access-date=August 7, 2021|website=[[National Health Service]]}}</ref> The kidneys filter about 150 quarts (170 liters) of blood daily, but most of it is returned to the blood stream with only 1-2 quarts (1-2 liters) ending up as urine,<ref>{{Cite web|title=Your Kidneys & How They Work {{!}} NIDDK|url=https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work|access-date=2021-08-07|website=National Institute of Diabetes and Digestive and Kidney Diseases|language=en-US}}</ref> which passes from the kidneys through the [[ureter]]s into the [[bladder]].

The [[smooth muscle]]s lining the ureter walls continuously tighten and relax through a process called [[peristalsis]], forcing small amounts of urine into the bladder every 10–15 seconds.

The bladder is a hollow balloon shaped organ located in the [[pelvis]]. It stores urine until the brain signals it to relax the [[Urethral sphincters|urinary sphincter]] and release the urine into the urethra starting [[urination]].<ref>{{Cite web|title=The Urinary Tract & How It Works {{!}} NIDDK|url=https://www.niddk.nih.gov/health-information/urologic-diseases/urinary-tract-how-it-works|access-date=2021-08-07|website=National Institute of Diabetes and Digestive and Kidney Diseases|language=en-US}}</ref> A normal bladder can hold up to 16 ounces (half a liter) for 3–5 hours comfortably.

Numerous [[Urologic disease|diseases affect the urinary system]] including [[Kidney stone disease|kidney stones]], which are formed when materials in the urine concentrate enough to form a solid mass, [[urinary tract infection]]s, which are infections of the urinary tract and can cause pain when urinating, frequent urination and even death if left untreated. [[Kidney failure|Renal failure]] occurs when the kidneys fail to adequately filter waste from the blood and can lead to death if not treated with [[Kidney dialysis|dialysis]] or [[kidney transplantation]].<ref>{{cite web |last1=Zimmermann |first1=Kim Ann |title=Urinary System: Facts, Functions & Diseases |url=http://www.livescience.com/27012-urinary-system.html |publisher=LiveScience |access-date=4 September 2016}}</ref> [[Cancer]] can affect the [[Bladder cancer|bladder]], [[Kidney cancer|kidneys]], [[Urethral cancer|urethra]] and [[Ureteral cancer|ureters]], with the latter two being far more rare.<ref>{{Cite journal|last=Yaxley|first=Julian P.|date=2016|title=Urinary tract cancers: An overview for general practice|journal=Journal of Family Medicine and Primary Care|volume=5|issue=3|pages=533–538|doi=10.4103/2249-4863.197258|issn=2249-4863|pmc=5290755|pmid=28217578 |doi-access=free }}</ref>