The ansa cervicalis is a loop of nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

s that are part of the cervical plexus

Cervical plexus

The cervical plexus is a plexus of the ventral rami of the first four cervical spinal nerves which are located from C1 to C4 cervical segment in the neck. They are located laterally to the transverse processes between prevertebral muscles from the medial side and vertebral from lateral side...

. It lies superficial to the internal jugular vein

Internal jugular vein

The two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck.-Path:On both sides and at the base of the brain, the inferior petrosal sinus and the sigmoid sinus join to form the internal jugular vein...

 in the carotid sheath

Carotid sheath

The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipose tissue immediately beneath the skin.The deep...

.

Branches from the ansa cervicalis innervate three of the four infrahyoid muscles: the sternohyoid muscle

Sternohyoid muscle

The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum, one of the paired strap muscles of the infrahyoid muscles serving to depress the hyoid bone...

, the sternothyroid muscle

Sternothyroid muscle

The Sternothyreoideus is shorter and wider than the Sternohyoideus, beneath which it is situated.It arises from the posterior surface of the manubrium sterni, below the origin of the Sternohyoideus, and from the edge of the cartilage of the first rib, and sometimes that of the second rib, it is...

, and the omohyoid muscle

Omohyoid muscle

The omohyoid muscle is a muscle at the front of the neck that consists of two bellies separated by an intermediate tendon. It belongs to the group of infrahyoid muscles...

. It does not innervate the thyrohyoid muscle, which receives its innervation from the Hypoglossal Nerve.

Roots

Two roots make up the ansa cervicalis.

• Superior root of ansa cervicalis
  Superior root of ansa cervicalis
  The superior root of the ansa cervicalis is formed by branches of spinal nerves [Cervical spinal nerve 1 and 2 ].These nerve fibers travel in the hypoglossal nerve before separating in the carotid triangle to form the superior root....
  
  
• Inferior root of ansa cervicalis
  Inferior root of ansa cervicalis
  The inferior root of the ansa cervicalis, also known as descendens cervicalis, is formed by fibers from spinal nerves C2 and C3.The inferior root gives off branches to the inferior belly of the omohyoid muscle, and the lower parts of the sternothyroid and sternohyoid muscles.-External links:* at...
  
  

External links

• Photo and description at Tufts University
  Tufts University
  Tufts University is a private research university located in Medford/Somerville, near Boston, Massachusetts. It is organized into ten schools, including two undergraduate programs and eight graduate divisions, on four campuses in Massachusetts and on the eastern border of France...