Editing Kidney (section)

== Structure ==
[[File:Surface projections of the organs of the trunk.png|thumb|300px|Image showing the human [[trunk (anatomy)|trunk]] with positions of the organs. The kidneys are at the [[vertebral level]] of T12 to L3. ]]
In humans, the kidneys are located high in the [[abdominal cavity]], one on each side of the [[vertebral column|spine]], and lie in a [[retroperitoneal]] position at a slightly oblique angle.<ref>{{cite web|url=http://science.howstuffworks.com/environmental/life/human-biology/kidney.htm|title=HowStuffWorks How Your Kidney Works|date=2001-01-10|access-date=2012-08-09|archive-date=2012-11-05|archive-url=https://web.archive.org/web/20121105124818/http://science.howstuffworks.com/environmental/life/human-biology/kidney.htm|url-status=live}}</ref> The asymmetry within the abdominal cavity, caused by the position of the [[liver]], typically results in the right kidney being slightly lower and smaller than the left, and being placed slightly more to the middle than the left kidney.<ref>{{cite web|url=http://www.indexedvisuals.com/scripts/ivstock/pic.asp?id=118-100 |title=Kidneys Location Stock Illustration |url-status=dead |archive-url=https://web.archive.org/web/20130927221414/http://www.indexedvisuals.com/scripts/ivstock/pic.asp?id=118-100 |archive-date=2013-09-27 }}</ref><ref>{{cite web | title = Kidney | work = BioPortfolio Ltd. | url = http://www.bioportfolio.com/indepth/Kidney.html | archive-url = https://web.archive.org/web/20080210070807/http://www.bioportfolio.com/indepth/Kidney.html| archive-date= 10 February 2008 }}</ref><ref name="pmid20030823">{{cite journal | vauthors = Glodny B, Unterholzner V, Taferner B, Hofmann KJ, Rehder P, Strasak A, Petersen J | title = Normal kidney size and its influencing factors - a 64-slice MDCT study of 1.040 asymptomatic patients | journal = BMC Urology | volume = 9 | issue = 1 | pages = 19 | date = December 2009 | pmid = 20030823 | pmc = 2813848 | doi = 10.1186/1471-2490-9-19 | doi-access = free }}</ref> The left kidney is approximately at the vertebral level [[thoracic vertebrae|T12]] to [[lumbar vertebrae|L3]],<ref>{{cite report | title = Bålens ytanatomy | trans-title = Superficial anatomy of the trunk | language = Swedish | vauthors = Dragomir A, Hjortberg M, Romans GM | work = Section for human anatomy at the Department of Medical Biology, Uppsala University, Sweden }}</ref> and the right is slightly lower. The right kidney sits just below the [[thoracic diaphragm|diaphragm]] and posterior to the [[liver]]. The left kidney sits below the diaphragm and posterior to the [[spleen]]. On top of each kidney is an [[adrenal gland]]. The upper parts of the kidneys are partially protected by the 11th and 12th [[rib]]s. Each kidney, with its adrenal gland is surrounded by two layers of fat: the [[adipose capsule of kidney|perirenal fat]] present between renal fascia and renal capsule and [[pararenal fat]] superior to the [[renal fascia]].

The human kidney is a bean-shaped structure with a [[wikt:convex|convex]] and a [[wikt:concave|concave]] border.<ref>{{Cite web |title=Renal system |url=https://www.britannica.com/science/human-renal-system |access-date=2022-05-22 |website=Britannica |language=en |archive-date=2022-05-31 |archive-url=https://web.archive.org/web/20220531015045/https://www.britannica.com/science/human-renal-system |url-status=live }}</ref> A recessed area on the concave border is the [[renal hilum]], where the [[renal artery]] enters the kidney and the [[renal vein]] and [[ureter]] leave. The kidney is surrounded by tough fibrous tissue, the [[renal capsule]], which is itself surrounded by [[adipose capsule of kidney|perirenal fat]], [[renal fascia]], and [[pararenal fat]]. The anterior (front) surface of these tissues is the [[peritoneum]], while the posterior (rear) surface is the [[transversalis fascia]].

The superior pole of the right kidney is adjacent to the liver. For the left kidney, it is next to the [[spleen]]. Both, therefore, move down upon inhalation.

{|class="wikitable"
|rowspan=2| '''Sex''' ||colspan=2 align="center"| '''Weight''', standard [[reference range]]
|-
|align="center"| '''Right kidney''' ||align="center"| '''Left kidney'''
|-
| Male<ref name="MolinaDiMaio2012">{{cite journal | vauthors = Molina DK, DiMaio VJ | title = Normal organ weights in men: part II – the brain, lungs, liver, spleen, and kidneys | journal = The American Journal of Forensic Medicine and Pathology | volume = 33 | issue = 4 | pages = 368–372 | date = December 2012 | pmid = 22182984 | doi = 10.1097/PAF.0b013e31823d29ad | s2cid = 32174574 }}</ref> || {{convert|80-160|g|oz|frac=4|abbr=on}} || {{convert|80-175|g|oz|frac=4|abbr=on}}
|-
| Female<ref name="MolinaDiMaio2015">{{cite journal | vauthors = Molina DK, DiMaio VJ | title = Normal Organ Weights in Women: Part II-The Brain, Lungs, Liver, Spleen, and Kidneys | journal = The American Journal of Forensic Medicine and Pathology | volume = 36 | issue = 3 | pages = 182–187 | date = September 2015 | pmid = 26108038 | doi = 10.1097/PAF.0000000000000175 | s2cid = 25319215 }}</ref> || {{convert|40-175|g|oz|frac=4|abbr=on}} || {{convert|35-190|g|oz|frac=4|abbr=on}}
|}
A Danish study measured the median renal length to be {{convert|11.2|cm|in|frac=16|abbr=on}} on the left side and {{convert|10.9|cm|in|frac=16|abbr=on}} on the right side in adults. Median renal volumes were {{cvt|146|cm3|cuin|frac=16}} on the left and {{cvt|134|cm3|cuin|frac=16}} on the right.<ref>{{cite journal | vauthors = Emamian SA, Nielsen MB, Pedersen JF, Ytte L | title = Kidney dimensions at sonography: correlation with age, sex, and habitus in 665 adult volunteers | journal = AJR. American Journal of Roentgenology | volume = 160 | issue = 1 | pages = 83–86 | date = January 1993 | pmid = 8416654 | doi = 10.2214/ajr.160.1.8416654 | doi-access =  }}</ref>

===Gross anatomy===
[[File:KidneyStructures PioM.svg|thumb|300px|right|
<div class="center">
1.&nbsp;[[Renal pyramid]] •
2.&nbsp;[[Interlobular artery]] •
3.&nbsp;[[Renal artery]] •
4.&nbsp;[[Renal vein]]
5.&nbsp;[[Renal hilum]] •
6.&nbsp;[[Renal pelvis]] •
7.&nbsp;[[Ureter]] •
8.&nbsp;[[Minor calyx]] •
9.&nbsp;[[Renal capsule]] •
10.&nbsp;[[Inferior renal capsule]] •
11.&nbsp;[[Superior renal capsule]] •
12.&nbsp;[[Interlobular vein]]{{citation needed|date=June 2022}} •
13.&nbsp;[[Nephron]] •
14.&nbsp;[[Renal sinus]] •
15.&nbsp;[[Major calyx]] •
16.&nbsp;[[Renal papilla]] •
17.&nbsp;[[Renal column]]
</div>]]
The functional substance, or [[Parenchyma#Renal parenchyma|parenchyma]], of the human kidney is divided into two major structures: the outer [[renal cortex]] and the inner [[renal medulla]]. Grossly, these structures take the shape of eight to 18 cone-shaped [[renal lobe]]s, each containing renal cortex surrounding a portion of medulla called a [[renal pyramid]].<ref name="boron">{{cite book | vauthors = Boron WF |title=Medical Physiology: A Cellular And Molecular Approach |publisher=Elsevier/Saunders |year=2004 |isbn=978-1-4160-2328-9 }}</ref> Between the renal pyramids are projections of cortex called [[renal column]]s.

The tip, or [[renal papilla|papilla]], of each pyramid empties urine into a [[minor calyx]]; minor calyces empty into [[major calyces]], and major calyces empty into the [[renal pelvis]]. This becomes the ureter. At the hilum, the ureter and renal vein exit the kidney and the renal artery enters. Hilar fat and lymphatic tissue with lymph nodes surround these structures. The hilar fat is contiguous with a fat-filled cavity called the [[renal sinus]]. The renal sinus collectively contains the renal pelvis and calyces and separates these structures from the renal medullary tissue.<ref>{{cite book | vauthors = Clapp WL | chapter = Renal Anatomy | veditors = Zhou XJ, Laszik Z, Nadasdy T, D'Agati VD, Silva FG | title = Silva's Diagnostic Renal Pathology | location = New York| publisher = Cambridge University Press | date = 2009 | isbn = 978-0-521-87702-2 }}</ref>

The kidneys possess no overtly moving structures.

<gallery mode="packed">
File:Right kidney seen on abdominal ultrasound.jpg|Normal adult right kidney as seen on [[abdominal ultrasound]] with a pole to pole measurement of 9.34&nbsp;cm
File:CTscankidney.jpg|A [[CT scan]] of the abdomen showing the position of the kidneys. The left cross-section in the upper abdomen shows the [[liver]] on the left side of scan (right side of body). Center: cross-section showing the kidneys below the liver and spleen. Right: further cross-section through the left kidney.
File:Slide42222.JPG|Image showing the structures that the kidney lies near
File:Left kidney.jpg|Cross-section through a [[cadaver]]ic specimen showing the position of the kidneys
</gallery>

=== Blood supply ===
{{main|Renal circulation}}
The kidneys receive blood from the [[renal artery|renal arteries]], left and right, which branch directly from the [[abdominal aorta]]. The kidneys receive approximately 20–25% of [[cardiac output]] in adult human.<ref name="boron"/><ref>{{Citation |title=Urinary system |date=2015 |url=https://www.cambridge.org/core/books/design-of-mammals/urinary-system/E76848B86DA00C151DA92EDD8AB2F418 |work=The Design of Mammals: A Scaling Approach |pages=195–203 |editor-last=Prothero |editor-first=John William |place=Cambridge |publisher=Cambridge University Press |doi=10.1017/CBO9781316275108.016 |isbn=978-1-107-11047-2 |access-date=2022-06-25 |archive-date=2018-06-17 |archive-url=https://web.archive.org/web/20180617094738/https://www.cambridge.org/core/books/design-of-mammals/urinary-system/E76848B86DA00C151DA92EDD8AB2F418 |url-status=live }}</ref><ref>{{Cite book |last1=Martini |first1=Frederic |title=Human Anatomy |last2=Tallitsch |first2=Robert B. |last3=Nath |first3=Judi L. |publisher=Pearson |year=2017 |isbn=9780134320762 |edition=9th |pages=689}}</ref> Each renal artery branches into segmental arteries, dividing further into [[interlobar arteries]], which penetrate the renal capsule and extend through the renal columns between the renal pyramids. The interlobar arteries then supply blood to the [[arcuate arteries]] that run through the boundary of the cortex and the medulla. Each arcuate artery supplies several [[interlobular]] arteries that feed into the [[afferent arteriole]]s that supply the glomeruli.

Blood drains from the kidneys, ultimately into the [[inferior vena cava]]. After filtration occurs, the blood moves through a small network of small veins ([[venules]]) that converge into [[interlobular veins]]. As with the arteriole distribution, the veins follow the same pattern: the interlobular provide blood to the [[arcuate veins]] then back to the [[interlobar veins]], which come to form the [[renal vein]]s which exit the kidney.

===Nerve supply===
The kidney and [[nervous system]] communicate via the [[renal plexus]], whose fibers course along the renal arteries to reach each kidney.<ref name="Bard">{{cite book |vauthors=Bard J, Vize PD, Woolf AS |title=The kidney: from normal development to congenital disease |publisher=Academic Press |location=Boston |year=2003 |page=154 |isbn=978-0-12-722441-1 |url=https://books.google.com/books?id=ctOm-cPwo60C&pg=PA154 |access-date=2020-10-19 |archive-date=2023-08-17 |archive-url=https://web.archive.org/web/20230817171609/https://books.google.com/books?id=ctOm-cPwo60C&pg=PA154 |url-status=live }}</ref> Input from the [[sympathetic nervous system]] triggers [[vasoconstriction]] in the kidney, thereby reducing [[renal blood flow]].<ref name="Bard"/> The kidney also receives input from the [[parasympathetic nervous system]],<ref>{{Cite journal |last1=Cheng |first1=Xiaofeng |last2=Zhang |first2=Yongsheng |last3=Chen |first3=Ruixi |last4=Qian |first4=Shenghui |last5=Lv |first5=Haijun |last6=Liu |first6=Xiuli |last7=Zeng |first7=Shaoqun |date=December 2022 |title=Anatomical Evidence for Parasympathetic Innervation of the Renal Vasculature and Pelvis |journal=Journal of the American Society of Nephrology |language=en |volume=33 |issue=12 |pages=2194–2210 |doi=10.1681/ASN.2021111518 |issn=1046-6673 |pmc=9731635 |pmid=36253054}}</ref> by way of the renal branches of the [[vagus nerve]]; the function of this is yet unclear.<ref name="Bard"/><ref>{{cite journal | vauthors = Schrier RW, Berl T | title = Mechanism of the antidiuretic effect associated with interruption of parasympathetic pathways | journal = The Journal of Clinical Investigation | volume = 51 | issue = 10 | pages = 2613–2620 | date = October 1972 | pmid = 5056657 | pmc = 332960 | doi = 10.1172/JCI107079 }}</ref> Sensory input from the kidney travels to the T10–11 levels of the [[spinal cord]] and is sensed in the corresponding [[dermatome (anatomy)|dermatome]].<ref name="Bard"/> Thus, pain in the flank region may be referred from corresponding kidney.<ref name="Bard"/>

=== Microanatomy ===

{{citation needed span|date=November 2023|[[Nephron]]s, the urine-producing functional structures of the kidney, span the cortex and medulla. The initial filtering portion of a nephron is the [[renal corpuscle]], which is located in the cortex. This is followed by a [[renal tubule]] that passes from the cortex deep into the medullary pyramids. Part of the renal cortex, a [[medullary ray (anatomy)|medullary ray]] is a collection of renal tubules that drain into a single [[collecting duct]].}}

Renal [[histology]] is the study of the [[microscopic]] structure of the kidney. The adult human kidney contains at least 26 distinct [[Cell type|cell types]],<ref>{{Cite Q|Q34534499}}</ref> including epithelial, endothelial, stromal and smooth muscle cells. Distinct cell types include:
*[[Kidney glomerulus parietal cell]]
*[[Kidney glomerulus podocyte]]
*[[Intraglomerular mesangial cell]]
*[[Extraglomerular mesangial cell]]
*[[Juxtaglomerular cell]]
*[[Kidney proximal tubule brush border cell]]
*[[Loop of Henle thin segment cell]]
*[[Thick ascending limb]] cell
*[[Kidney distal tubule cell]]
*[[Collecting duct system#Cells|Collecting duct principal cell]]
*[[Collecting duct system#Cells|Collecting duct intercalated cell]]
*Interstitial kidney cells