Ansa Cervicalis

• This is a thin nerve loop that lies embedded in the anterior wall of the carotid sheath over the lower part of the laryrrx.
• It supplies the infrahyoid muscles

Formation
It is formed by a superior and an inferior root.

• The superior root is the continuation of the descending branch of the hypoglossal nerve.
  Its fibres are derived from the first cervical nerve. This root descends over the internal carotid artery and the common carotid artery.
  
  

• The inferior root or descending cervical nerve is derived from second and third cervical spinal nerves.
  As this root descends, it winds round the internal jugular vein, and then continues anteroinferiorly to join the superior root in front of the common carotid artery

Distribution

• Superior root: To the superior belly of the omohyoid.
  
• Ansa cervicalis: To the sternohyoid, the sternothyroid and the inferior belly of the omohyoid.
  
  
• Note that the thyrohyoid and geniohyoid are supplied by separate branches from the first cervical nerve through the hypoglossal nerve 

Watch the lectures on YouTube:

Cervical Plexus | Formation, Branches, Communicating Branches | Ansa Cervicalis|