Anatomical variation - Revision history

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	{{Short description\|~~Difference between the anatomical structures~~}}		{{Short description\|Differences in human anatomy among individuals}}
	An '''anatomical variation''', '''anatomical variant''', or '''anatomical variability''' is a difference between the [[Anatomy\|anatomical]] structures of [[animal]]s from the same [[species]]. The variations are seen as normal in the sense that they are found consistently among different individuals, are mostly without symptoms, and are termed anatomical variations rather than abnormalities.<ref name="Atlases">{{~~cite web \|title=Anatomic variants \|url=https://www.anatomyatlases.org/AnatomicVariants/Introduction.shtml~~}}~~</ref> Some variations are found in different species such as [[polydactyly]], having more than the usual number of digits.~~		{{Anatomy}}

	Anatomical ~~variations are mainly caused by [[genetics]] and may vary considerably between different [[population]]s. The rate of~~ variation ~~considerably differs between single~~ [[~~organ (~~anatomy~~)\|organ~~]]~~s, particularly~~ in ~~[[muscle]]s~~.~~<ref name="Atlases"/> Knowledge of anatomical~~ variations ~~is important in order to distinguish them from pathological conditions~~.		'''Anatomical variation''' refers to the differences in the [[anatomy]] of individuals within the same species. These variations are common and can occur in any part of the body. They are usually harmless and are considered normal variations rather than abnormalities or pathologies.

	~~A very early paper published in 1898, presented anatomic variations to have a wide range and significance,<ref name~~=~~"Cunningham">{{cite journal \|last1~~=~~Cunningham \|first1~~=~~DJ \|title~~=~~The Significance of~~ Anatomical ~~Variations~~. ~~\|journal=Journal of Anatomy and Physiology \|date=October 1898 \|volume=33 \|issue=Pt 1 \|pages=1–9 \|pmid=17232348\|pmc=1327970 }}</ref> and before~~ the ~~use of~~ [[~~X-ray~~]] ~~technology~~, ~~anatomic variations were mostly only found on~~ [[~~cadaver~~]] ~~studies~~. ~~The use of~~ imaging ~~techniques have defined many such variations.<ref name="Bell">{{cite web \|last1=Bell \|first1=Daniel J~~. ~~\|title=Anatomical variants {{!}} Radiology Reference Article {{!}} Radiopaedia.org \|url=https://radiopaedia.org/articles/anatomical-variants?lang=gb \|website=Radiopaedia}}</ref>~~		==Overview==
			Anatomical variations are deviations from the "standard" anatomy that is often depicted in textbooks. These variations can be found in the [[musculoskeletal system]], [[vascular system]], [[nervous system]], and other organ systems. They are important for [[medical education]], [[surgery]], and [[diagnostic imaging]] because they can affect clinical procedures and outcomes.

	==~~Variants~~ of ~~structures~~==		==Types of Anatomical Variations==
	~~{{Main\|List of anatomical variations}}~~
	~~===Muscles===~~
	[[Friedrich Wilhelm Kopsch\|Kopsch]] gave a detailed listing of muscle variations. These included the absence of muscles; muscles that were doubled; muscles that were divided into two or more parts; an increase or decrease in the origin or insertion of the muscle; and the joining to adjacent organs.<ref name="Atlases"/>

	~~The~~ [[~~palmaris longus muscle~~]] in the ~~forearm is sometimes absent~~, as is the [[~~plantaris muscle~~]] in the ~~leg~~.~~<ref name="Saladin2">{{cite book \|last1=Saladin \|first1=K \|title=Anatomy and Physiology \|date=2012 \|isbn=9780073378251 \|pages=14–15 \|edition=6th}}</ref>~~		===Musculoskeletal Variations===
			Variations in the [[musculoskeletal system]] include differences in the number, size, and shape of bones and muscles. For example, some individuals may have an extra [[rib]] or a variation in the [[vertebrae]]. Muscle variations can include differences in the origin, insertion, or presence of certain muscles, such as the [[palmaris longus]] muscle, which is absent in a significant portion of the population.

	The [[~~sternalis muscle~~]] is ~~a variant that lies~~ in ~~front~~ of the [[~~pectoralis major~~]] and ~~may show up on a~~ [[~~mammogram~~]].~~<ref>{{Cite web\|url=https://radiopaedia.org\|title=Sternalis muscle\|last=Garg\|first=T\|website=radiopaedia.org\|access-date=19 September 2019}}</ref>~~		===Vascular Variations===
			The [[vascular system]] is known for its numerous variations. These can include differences in the branching patterns of [[arteries]] and [[veins]]. For instance, the [[circle of Willis]] in the brain can have multiple configurations, and the [[renal arteries]] can vary in number and origin.

	===~~Bones~~===		===Nervous System Variations===
	~~Usually there are five~~ [[~~lumbar vertebra~~]]~~e but sometimes there are six~~, and ~~sometimes there are four~~.~~<ref name="Saladin2"/>~~		Variations in the [[nervous system]] can include differences in the structure and branching of [[nerves]]. An example is the [[sciatic nerve]], which can have different branching patterns that may affect surgical approaches and outcomes.

	===~~Joints~~===		===Organ Variations===
	A [[~~discoid meniscus]] is a rare thickened [[lateral meniscus~~]] in the [[~~knee joint~~]] ~~that~~ can ~~sometimes be swollen~~ and ~~painful~~.<ref name="Kim">{{cite journal \|last1=Kim \|first1=JG \|last2=Han \|first2=SW \|last3=Lee \|first3=DH \|title=Diagnosis and Treatment of Discoid Meniscus. \|journal=Knee Surgery & Related Research \|date=2016-12-01 \|volume=28 \|issue=4 \|pages=255–262 \|doi=10.5792/ksrr.16.050 \|pmid=27894171\|pmc=5134787 \|doi-access=free }}</ref>		Variations in [[internal organs]] can include differences in size, shape, and position. For example, the [[kidneys]] can vary in their location and number, with some individuals having a horseshoe kidney or an additional kidney.

	==~~=Organs=~~==		==Clinical Significance==
	~~The~~ [[~~lung~~]]~~s are subject~~ to ~~anatomical variations~~.~~<ref name="Moore">{{cite book \|last1=Moore \|first1=K \|title=Clinically oriented anatomy \|date=2018 \|isbn=9781496347213 \|page=342 \|edition=Eighth}}</ref>~~		Understanding anatomical variations is crucial for [[healthcare professionals]] to avoid misdiagnosis and to plan appropriate surgical interventions. Variations can affect the presentation of [[symptoms]] and the interpretation of [[imaging studies]]. They are also important in the context of [[anatomical education]] and research.

	~~==Clinical significance==~~
	[[~~Accessory bone\|Accessory~~]] ~~small bones called ''ossicles'' may be mistaken for~~ [[~~avulsion fracture~~]]s.~~{{Citation needed\|date=July 2021}}~~

	~~==See~~ also==
	* [[~~Supernumerary body part~~]]

	~~==References==~~
	~~{{Reflist}}~~

	~~==External links==~~
	* [http://www.anatomyatlases.org/AnatomicVariants/AnatomyHP.~~shtml Atlas of human anatomical variations]~~

			==Related Pages==
			* [[Anatomy]]
			* [[Human anatomy]]
			* [[Congenital disorder]]
			* [[Medical imaging]]
			* [[Surgery]]

	[[Category:Anatomy]]		[[Category:Anatomy]]
	~~{{dictionary-stub1}}~~		[[Category:Human anatomy]]
	~~{{No image}}~~		[[Category:Medical education]]

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{{Short description|Difference between the anatomical structures}}
An '''anatomical variation''', '''anatomical variant''', or '''anatomical variability''' is a difference between the [[Anatomy|anatomical]] structures of [[animal]]s from the same [[species]]. The variations are seen as normal in the sense that they are found consistently among different individuals, are mostly without symptoms, and are termed anatomical variations rather than abnormalities.<ref name="Atlases">{{cite web |title=Anatomic variants |url=https://www.anatomyatlases.org/AnatomicVariants/Introduction.shtml}}</ref> Some variations are found in different species such as [[polydactyly]], having more than the usual number of digits.

Anatomical variations are mainly caused by [[genetics]] and may vary considerably between different [[population]]s. The rate of variation considerably differs between single [[organ (anatomy)|organ]]s, particularly in [[muscle]]s.<ref name="Atlases"/> Knowledge of anatomical variations is important in order to distinguish them from pathological conditions.

A very early paper published in 1898, presented anatomic variations to have a wide range and significance,<ref name="Cunningham">{{cite journal |last1=Cunningham |first1=DJ |title=The Significance of Anatomical Variations. |journal=Journal of Anatomy and Physiology |date=October 1898 |volume=33 |issue=Pt 1 |pages=1–9 |pmid=17232348|pmc=1327970 }}</ref> and before the use of [[X-ray]] technology, anatomic variations were mostly only found on [[cadaver]] studies. The use of imaging techniques have defined many such variations.<ref name="Bell">{{cite web |last1=Bell |first1=Daniel J. |title=Anatomical variants {{!}} Radiology Reference Article {{!}} Radiopaedia.org |url=https://radiopaedia.org/articles/anatomical-variants?lang=gb |website=Radiopaedia}}</ref>

==Variants of structures==
{{Main|List of anatomical variations}}
===Muscles===
[[Friedrich Wilhelm Kopsch|Kopsch]] gave a detailed listing of muscle variations. These included the absence of muscles; muscles that were doubled; muscles that were divided into two or more parts; an increase or decrease in the origin or insertion of the muscle; and the joining to adjacent organs.<ref name="Atlases"/>

The [[palmaris longus muscle]] in the forearm is sometimes absent, as is the [[plantaris muscle]] in the leg.<ref name="Saladin2">{{cite book |last1=Saladin |first1=K |title=Anatomy and Physiology |date=2012 |isbn=9780073378251 |pages=14–15 |edition=6th}}</ref>

The [[sternalis muscle]] is a variant that lies in front of the [[pectoralis major]] and may show up on a [[mammogram]].<ref>{{Cite web|url=https://radiopaedia.org|title=Sternalis muscle|last=Garg|first=T|website=radiopaedia.org|access-date=19 September 2019}}</ref>

===Bones===
Usually there are five [[lumbar vertebra]]e but sometimes there are six, and sometimes there are four.<ref name="Saladin2"/>

===Joints===
A [[discoid meniscus]] is a rare thickened [[lateral meniscus]] in the [[knee joint]] that can sometimes be swollen and painful.<ref name="Kim">{{cite journal |last1=Kim |first1=JG |last2=Han |first2=SW |last3=Lee |first3=DH |title=Diagnosis and Treatment of Discoid Meniscus. |journal=Knee Surgery & Related Research |date=2016-12-01 |volume=28 |issue=4 |pages=255–262 |doi=10.5792/ksrr.16.050 |pmid=27894171|pmc=5134787 |doi-access=free }}</ref>

===Organs===
The [[lung]]s are subject to anatomical variations.<ref name="Moore">{{cite book |last1=Moore |first1=K |title=Clinically oriented anatomy |date=2018 |isbn=9781496347213 |page=342 |edition=Eighth}}</ref>

==Clinical significance==
[[Accessory bone|Accessory]] small bones called ''ossicles'' may be mistaken for [[avulsion fracture]]s.{{Citation needed|date=July 2021}}

==See also==
* [[Supernumerary body part]]

==References==
{{Reflist}}

==External links==
* [http://www.anatomyatlases.org/AnatomicVariants/AnatomyHP.shtml Atlas of human anatomical variations]

[[Category:Anatomy]]
{{dictionary-stub1}}