Ansa cervicalis

The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin.

Ansa cervicalis
Ansa cervicalis. Superior root labeled as "descending hypoglossal," Inferior root labeled as "descending cervical."
Details
Innervatessternohyoid muscle, sternothyroid muscle, omohyoid muscle
Identifiers
LatinAnsa cervicalis, ansa hypoglossi
TAA14.2.02.013
FMA55142
Anatomical terms of neuroanatomy

Branches from the ansa cervicalis innervate most of the infrahyoid muscles, including the sternothyroid muscle, sternohyoid muscle, and the omohyoid muscle. Note that the thyrohyoid muscle, which is also an infrahyoid muscle and the geniohyoid muscle which is a suprahyoid muscle are innervated by cervical spinal nerve 1 via the hypoglossal nerve.

Roots

Two roots make up the ansa cervicalis, a superior root, and an inferior root.

Ansa cervicalis

The superior root of the ansa cervicalis is formed from cervical spinal nerve 1 of the cervical plexus. These nerve fibers travel in the hypoglossal nerve before separating in the carotid triangle to form the superior root.

The superior root goes around the occipital artery and then descends on the carotid sheath. It sends off branches to the superior belly of the omohyoid muscle, and the upper parts of the sternothyroid and sternohyoid muscles and is then joined by the inferior root.

The inferior root of the ansa cervicalis, also known as descendens cervicalis, is formed by fibers from spinal nerves C2 and C3.

The inferior root gives off branches to the inferior belly of the omohyoid muscle, and the lower parts of the sternothyroid and sternohyoid muscles.

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.
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References
  • "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
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