- Ansa cervicalis (ansa hypoglossi): U-shaped nerve loop in the carotid triangle, embedded in the anterior wall of the carotid sheath.
- Formed from ventral rami of C1, C2 and C3 spinal nerves.
Roots
- Two roots unite to form the loop: superior root and inferior root, joining in front of the common carotid artery at the level of the cricoid cartilage.
Differences between the superior and inferior roots of the ansa cervicalis
Point
Origin
- Superior root (descendens hypoglossi)
- Descending branch of the hypoglossal nerve, carrying C1 fibres
- Inferior root (descendens cervicalis)
- Ventral rami of C2 and C3
Course
- Superior root (descendens hypoglossi)
- Descends over the internal and common carotid arteries
- Inferior root (descendens cervicalis)
- Winds round the internal jugular vein, then passes anteroinferiorly to join the superior root