2. 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
3. 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
