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Formation and Muscles Supplied by Ansa Cervicalis
Ansa cervicalis is a U-shaped nerve loop which is embedded in the anterior wall of the carotid sheath.
Formation: It is formed by two roots which arise from ventral rami of C1, C2 and C3 spinal nerves. The roots of ansa cervicalis are:
- Superior root (descendens hypoglossi) is formed by the fibers from C1 spinal nerve which join the hypoglossal nerve and later leave it and descends anterior to the carotid sheath.
- Inferior root (descendens cervicalis) is formed by C2 and C3 spinal nerves. It spirals around the lateral margin of internal jugular vein and turns medially to join the superior root in front of the common carotid artery at the level of cricoid cartilage.
Muscles supplied: It supplies all the infrahyoid muscles except thyrohyoid which is supplied by nerve to thyrohyoid (C1) which accompanies hypoglossal nerve.
- Superior root supplies branch to superior belly of omohyoid.
- The loop supplies branches to sternohyoid, sternothyroid and inferior belly of the omohyoid.
