Ansa cervicalis
The ansa cervicalis 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 and an inferior root - that unite distally, forming a loop. It is situated anterior to the carotid sheath.
Branches of the ansa cervicalis innervate three of the four infrahyoid muscles: the sternothyroid, sternohyoid, and omohyoid muscles.
Its name means "handle of the neck" in Latin.
Anatomy
The ansa cervicalis is typically embedded within the anterior wall of the carotid sheath anterior to the internal jugular vein.''''''Superior root
The superior root of the ansa cervicalis is by fibres of the cervical spinal nerve 1 that have joined and run with the hypoglossal nerve (CN XII) for some distance before' progressively' branching off the CN XII in the carotid triangle to form the superior root.'The superior root is situated within the carotid triangle.' It passes anterior-ward between the internal carotid artery and the common carotid artery.' It curves around the occipital artery before descending upon the anterior aspect of the internal carotid artery and the common carotid artery.' on the carotid sheath. It issues a branch to the superior belly of the omohyoid muscle, and the upper parts of the sternothyroid and sternohyoid muscles before uniting with the inferior root.
Inferior root
The inferior root of the ansa cervicalis is formed by the union of fibers of the anterior rami spinal cervical nerves C2-C3 that unite as part of the cervical plexus.'The inferior root curves posteroanteriorly around' the lateral side of the internal jugular vein before descending to unite with the superior root upon the the internal jugular vein. It may occasionally pass anterior in between the internal jugular vein and the internal carotid artery.''''''