View source for Thenar eminence

{{Short description|Mound at the base of the thumb formed by the intrinsic group of muscles}}
{{Anatomy terms}}
{{Page numbers needed|date=January 2011}}

{{Infobox muscle
| Name        = Thenar eminence
| Latin       = eminentia thenaris
| Image       = Gray423.png
| Caption     = The mucous sheaths of the tendons on the anterior surface of the [[wrist]] and [[finger|digits]]
| Image2      = Carpal-Tunnel.svg
| Caption2    = Transverse section across the [[wrist]] and [[finger|digits]] (muscles of thumb labeled at upper left)
| Origin      =
| Insertion   =
| Blood       = [[Superficial palmar arch]]
| Nerve       = [[Median nerve]]
| Action      = Control movement of the [[thumb]]
| Antagonist  =
| part_of = [[Hand]]
}}

The '''thenar eminence''' is the mound formed at the base of the [[thumb]] on the palm of the hand by the [[muscles of the thumb#Intrinsic|intrinsic group]] of [[muscles of the thumb]].<ref name="Gupta">{{cite journal |last1=Gupta |first1=S |last2=Michelsen-Jost |first2=H |title=Anatomy and function of the thenar muscles. |journal=Hand Clinics |date=February 2012 |volume=28 |issue=1 |pages=1–7 |doi=10.1016/j.hcl.2011.09.006 |pmid=22117918}}</ref> The skin overlying this region is the area stimulated when trying to elicit a [[palmomental reflex]]. The word thenar comes {{ety|grc|''θέναρ'' (thenar)|palm of the hand}}.<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dqe%2Fnar θέναρ]</ref>

==Structure==
The following three muscles are considered part of the thenar eminence:<ref name="titleIntrinsic Muscles of the Hand&nbsp;— Wheeless Textbook of Orthopaedics">{{cite web |url=http://www.wheelessonline.com/ortho/intrinsic_muscles_of_the_hand |title=Intrinsic Muscles of the Hand&nbsp;— Wheeless' Textbook of Orthopaedics |access-date=2008-01-16 }}</ref>
* [[Abductor pollicis brevis]] [[abduction (anatomy)|abducts]] the thumb. This muscle is the most [[superficial (anatomy)|superficial]] of the thenar group.
* [[Flexor pollicis brevis]], which lies next to the abductor, will [[flexion|flex]] the thumb, curling it up in the palm. (The [[flexor pollicis longus]], which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.)
* [[Opponens pollicis]] lies deep to abductor pollicis brevis. As its name suggests it [[Anatomical terms of motion|opposes]] the thumb, bringing it against the fingers. This is a very important movement, as most of human hand dexterity comes from this action.

Another muscle that controls movement of the thumb is [[adductor pollicis]]. It lies deeper and more [[distal]] to flexor pollicis brevis. Despite the name, adductor pollicis is chiefly responsible for rotation and opposition. This muscle is not in the thenar group of muscles, and is supplied by the [[ulnar nerve]] instead.<ref name="titleApplied MSK anatomy of the hand">{{cite web |url=http://www.med.mun.ca/anatomyts/msk/hand.htm |title=Applied MSK anatomy of the hand |access-date=2008-01-16 |archive-url = https://web.archive.org/web/20080101140737/http://www.med.mun.ca/anatomyts/msk/hand.htm <!-- Bot retrieved archive --> |archive-date = 2008-01-01}}</ref>

===Nerve supply===
The opponens pollicis and abductor pollicis brevis are normally innervated by the [[recurrent branch of the  median nerve]].

The flexor pollicis brevis has two heads: a superficial and a deep head. The superficial head is usually innervated by the recurrent branch of the [[median nerve]].<ref name=":0">{{Citation|last1=Fernández-de-las-Peñas|first1=César|title=8 - Deep dry needling of the arm and hand muscles|date=2012-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780702046018000086|work=Trigger Point Dry Needling|pages=107–118|editor-last=Dommerholt|editor-first=Jan|place=Oxford|publisher=Churchill Livingstone|language=en|doi=10.1016/b978-0-7020-4601-8.00008-6|isbn=978-0-7020-4601-8|access-date=2020-10-25|last2=Iglesias|first2=Javier González|last3=Gröbli|first3=Christian|last4=Weissmann|first4=Ricky|editor2-last=Fernández-de-las-Peñas|editor2-first=César|url-access=subscription}}</ref> The deep part is often innervated by the [[deep branch of ulnar nerve]] ([[Cervical spinal nerve 8|C8]] and [[Thoracic spinal nerve 1|T1]] roots).<ref name=":1">{{Citation|last=Strickland|first=James W.|title=Chapter 2 - Anatomy and Kinesiology of the Hand|date=2006-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780323031868500058|work=Hand Function in the Child (Second Edition)|pages=21–44|editor-last=Henderson|editor-first=Anne|place=Saint Louis|publisher=Mosby|language=en|doi=10.1016/b978-032303186-8.50005-8|isbn=978-0-323-03186-8|access-date=2020-10-25|editor2-last=Pehoski|editor2-first=Charlane|url-access=subscription}}</ref><ref name="Gray37th630p">[[Gray's Anatomy]] 37th British Edition, p. 630</ref>

There are normal variations. In a [[Cannieu-Riche anastomosis]], fibers from the deep branch of ulnar nerve innervate the opponens pollicis and/or abductor pollicis brevis. Regardless of their final innervation, the nerves that reach the thenar muscles arise from the C8 and T1 roots, pass through the lower trunk of the [[brachial plexus]], and then through the medial cord of the plexus.{{citation needed|date=December 2024}}

The adductor pollicis is typically innervated by the [[ulnar nerve]].

The ulnar nerve is exclusively responsible for the innervations of the [[hypothenar eminence]]. Both nerves contribute to the innervations of the [[midpalmar group]].<ref name="test">{{cite book
| last     = Van De Graaff | first = Kent M.
| title    = Human Anatomy | edition = 3rd
| location = Dubuque | publisher = Wm C Brown | year = 1992
| isbn     = 0-697-09716-1
}} Print.</ref>

The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve. The lateral two [[Lumbricals of the hand|lumbrical muscles]] are the other exception.

==Additional images==
<gallery>
 File:Slide8PPP.JPG|Thenar eminence
 File:Hand dissection 5.jpg|Carpal tunnel and thenar and hypothenar eminences
 File:Thenar eminence comparison anterior.jpg|Comparison, anterior
 File:Thenar eminence comparison posterior.jpg|Comparison, posterior
 File:Thenar eminence comparison thumbs.jpg|Comparison facing thumbs
</gallery>

==See also==
* [[Hypothenar eminence]]

==References==
{{Gray's|inline=1}}
{{Reflist|colwidth=30em}}

==External links==
* {{NormanAnatomy|lesson5mus&tendonsofhand}}

{{Muscles of upper limb}}
{{Authority control}}

{{DEFAULTSORT:Thenar Eminence}}
[[Category:Hand]]
[[Category:Muscles of the upper limb]]