The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

s that are part of the

cervical plexus The cervical plexus is a plexus of the anterior rami of the first four cervical spinal nerves which arise from C1 to C4 cervical segment in the neck. They are located laterally to the transverse processes between prevertebral muscles from the medi ...

. It lies superficial to the

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posteri ...

in the

carotid triangle The carotid triangle (or superior carotid triangle) is a portion of the anterior triangle of the neck. Coverings and boundaries It is bounded: * Posteriorly by the anterior border of the Sternocleidomastoid; * Anteroinferiorly, by the superior bel ...

. Its name means "handle of the neck" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

. Branches from the ansa cervicalis innervate most of the

infrahyoid muscles The infrahyoid muscles, or strap muscles, are a group of four pairs of muscles in the anterior (frontal) part of the neck. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles. Excluding the sternothyro ...

, including the

sternothyroid muscle The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid. Structure The sternothyroid arises from the ...

sternohyoid muscle The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternohyo ...

and the

omohyoid muscle The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to th ...

. Note that the

thyrohyoid muscle The thyrohyoid muscle is a small skeletal muscle on the neck. It originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone. It is supplied by the hypoglossal nerve, and a branch of the ventral rami ...

, which is also an infrahyoid muscle and the

geniohyoid muscle The geniohyoid muscle is a narrow muscle situated superior to the medial border of the mylohyoid muscle. It is named for its passage from the chin ("genio-" is a standard prefix for "chin") to the hyoid bone. Structure It arises from the infe ...

which is a suprahyoid muscle are innervated by

cervical spinal nerve 1 The cervical spinal nerve 1 (C1) is a spinal nerve of the cervical segment. ...

via the

hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated by ...

Roots

Two roots make up the ansa cervicalis, a superior root, and an inferior root.

The superior root of the ansa cervicalis is formed from

cervical spinal nerve 1 The cervical spinal nerve 1 (C1) is a spinal nerve of the cervical segment. ...

of the

. These nerve fibers travel in the

before separating in the

to form the superior root. The superior root goes around the

occipital artery The occipital artery arises from the external carotid artery opposite the facial artery. Its path is below the posterior belly of digastric to the occipital region. This artery supplies blood to the back of the scalp and sternocleidomastoid muscles ...

and then descends on the

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 adipo ...

. It sends off branches to the superior belly of the

, and the upper parts of the sternothyroid and

sternohyoid The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternoh ...

muscles and is then joined by the inferior root. The inferior root of the ansa cervicalis, also known as descendens cervicalis, is formed by fibers from

spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into th ...

s C2 and C3. The inferior root gives off branches to the inferior belly of the

, and the lower parts of the sternothyroid and

muscles.

Additional images

Image:Gray784.png, Cervical plexus shown in purple Image:Gray804.png, Plan of the cervical plexus. Image:Gray808.png, The right brachial plexus with its short branches, viewed from in front. Image:Cervical plexus.gif, Cervical plexus File:Slide1EBA.JPG, Muscles, arteries and nerves of neck.Newborn dissection.

References

* "Ansa cervicalis." ''Stedman's Medical Dictionary, 27th ed.'' (2000). * ''Gray's Anatomy: The Anatomical Basis of Clinical Practice.'' (2005).

External links

*
Photo and description
at

Tufts University Tufts University is a private research university on the border of Medford and Somerville, Massachusetts. It was founded in 1852 as Tufts College by Christian universalists who sought to provide a nonsectarian institution of higher learning. ...

* * https://web.archive.org/web/20080304085514/http://www.med.mun.ca/anatomyts/nerve/cerplex.htm {{Authority control Nerves of the head and neck