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Ansa cervicalis
Ansa cervicalis
	Ansa cervicalis. Superior root labeled as "descending hypoglossal," Inferior root labeled as "descending cervical."
Details
Innervates	Sternohyoid muscle,; sternothyroid muscle,; omohyoid muscle
Identifiers
Latin	ansa cervicalis,; ansa hypoglossi
TA98	A14.2.02.013
TA2	6376
FMA	55142
	Anatomical terms of neuroanatomy [edit on Wikidata]

The ansa cervicalis (or ansa hypoglossi in older literature^{[citation needed]}) is a loop formed by muscular branches of the cervical plexus formed by branches of cervical spinal nerves C1-C3. The ansa cervicalis has two roots - a superior root (formed by branch of C1) and an inferior root (formed by union of branches of C2 and C3) - that unite distally, forming a loop. It is situated anterior to the carotid sheath.^[1]^: 334

Branches of the ansa cervicalis innervate three of the four infrahyoid muscles: the sternothyroid, sternohyoid, and omohyoid muscles (note that the thyrohyoid muscle is the one infrahyoid muscle not innervated by the ansa cervicalis - it is instead innervated by cervical spinal nerve 1 via a separate thyrohyoid branch^[2]^{: 582, 600}).

Its name means "handle of the neck" in Latin.^{[citation needed]}

Anatomy

The ansa cervicalis is typically embedded within the anterior wall of the carotid sheath anterior to the internal jugular vein.^[1]^: 344

Superior root

The superior root of the ansa cervicalis (formerly known as descendens hypoglossi^[1]^: 500) is by fibres of the cervical spinal nerve 1 ^[1]^: 344^[3] (and, according to some sources, of cervical spinal nerve 2 as well^[3]) that have joined and run with the hypoglossal nerve (CN XII) for some distance before^[1]^: 344 progressively^[1]^: 369 branching off the CN XII in the carotid triangle to form the superior root.^[1]^: 344

The superior root is situated within the carotid triangle.^[1]^: 344 It passes anterior-ward between the internal carotid artery and the common carotid artery.^[1]^: 500 It curves around the occipital artery^{[citation needed]} before descending upon the anterior aspect of the internal carotid artery and the common carotid artery.^[1]^: 344 on the carotid sheath.^{[citation needed]} It issues a branch to the superior belly of the omohyoid muscle,^[1]^: 344 and the upper parts of the sternothyroid and sternohyoid muscles before uniting with the inferior root.^{[citation needed]}

Inferior root

The inferior root of the ansa cervicalis (formerly known as descendens cervicalis^[1]^: 500) is formed by the union of fibers of the anterior rami spinal cervical nerves C2-C3 that unite as part of the cervical plexus.^[1]^: 344

The inferior root curves posteroanteriorly around^[1]^: 344 the lateral side of the internal jugular vein^[1]^: 343 before descending to unite with the superior root upon the (inferior portion of) the internal jugular vein. It may occasionally pass anterior in between the internal jugular vein and the internal carotid artery.^[1]^: 344

Branches

Branches to the sternothyroid muscle, sternohyoid muscle, and inferior belly of the omohyoid muscle issue from the loop of the ansa cervicalis, whereas the branch for the superior belly of the omohyoid muscle arises from the superior root.^[1]^: 344

Additional images

Cervical plexus shown in purple
Plan of the cervical plexus.
The right brachial plexus with its short branches, viewed from in front.
Cervical plexus
Muscles, arteries and nerves of neck. Newborn dissection.

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). Elsevier Australia. ISBN 978-0-7295-3752-0.
^ Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). New York. ISBN 978-0-7020-7707-4. OCLC 1201341621.{{cite book}}: CS1 maint: location missing publisher (link)
^ ^a ^b Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2018). Clinically Oriented Anatomy (8th ed.). Wolters Kluwer. p. 1005. ISBN 978-1-4963-4721-3.

"Ansa cervicalis." Stedman's Medical Dictionary, 27th ed. (2000). ISBN 0-683-40007-X
Gray's Anatomy: The Anatomical Basis of Clinical Practice. (2005). ISBN 0-443-07168-3

External links

Anatomy figure: 25:03-08 at Human Anatomy Online, SUNY Downstate Medical Center
Photo and description at Tufts University
MedicalMnemonics.com: 1042
https://web.archive.org/web/20080304085514/http://www.med.mun.ca/anatomyts/nerve/cerplex.htm

[:022-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). Elsevier Australia. ISBN 978-0-7295-3752-0.

[:224-2] Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). New York. ISBN 978-0-7020-7707-4. OCLC 1201341621.{{cite book}}: CS1 maint: location missing publisher (link)

[:0-3] Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2018). Clinically Oriented Anatomy (8th ed.). Wolters Kluwer. p. 1005. ISBN 978-1-4963-4721-3.

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Ansa cervicalis