omohyoid muscle

The omohyoid muscle consists of muscle bellies that meet at an angle at the muscle's intermediate tendon.{{Cite book |last=Standring |first=Susan |url=https://www.worldcat.org/oclc/1201341621 |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |year=2020 |isbn=978-0-7020-7707-4 |edition=42nd |location=New York |pages=581–582 |oclc=1201341621}}

The inferior belly is narrow and flat band.

It arises from the superior border of scapula (near the scapular notch). It sometimes also arises from the superior transverse scapular ligament.

It is directed anteriorly and somewhat superiorly from its origin, extending across the inferior portion of the neck. It passes posterior to the sternocleidomastoid muscle to insert at the intermediate tendon.

The superior belly arises at the intermediate tendon. It extends nearly vertically superior-ward close to the lateral border of sternocleidomastoid muscle to insert at the inferior border of the body of hyoid bone (its site of insertion is lateral to that of the sternohyoid muscle).

The intermediate tendon is variable in length and form, and contains a variable amount of muscle tissue. It is anchored inferiorly to the clavicle and first rib by a band of deep cervical fascia that surrounds the intermediate tendon; this fascial fixation maintains the angle of the muscle.

It is typically situated at the level of the arch of cricoid cartilage, adjacent to the internal jugular vein.

The omohyoid is innervated by the ansa cervicalis of the cervical plexus.{{Citation|last1=McHanwell|first1=Steve|title=Chapter 7 - Localization of Motoneurons in the Spinal Cord|date=2009-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780123742476500110|work=The Spinal Cord|pages=94–114|editor-last=Watson|editor-first=Charles|place=San Diego|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-374247-6.50011-0|isbn=978-0-12-374247-6|access-date=2020-11-20|last2=Watson|first2=Charles|editor2-last=Paxinos|editor2-first=George|editor3-last=Kayalioglu|editor3-first=Gulgun|url-access=subscription}} The inferior belly is innervated by the ansa cervicalis itself (which is derived from cervical spinal nerves C1-C3), and the superior belly is innervated by the superior root of ansa cervicalis (which is derived from the first cervical spinal nerve (C1)).

The inferior belly of the omohyoid divides the posterior triangle of the neck into a occipital triangle (above) and a subclavian triangle (below).{{Citation |last1=Luna |first1=Mario A. |title=Chapter 11 - Cysts of the Neck, Unknown Primary Tumor, and Neck Dissection |date=2009-01-01 |url=http://www.sciencedirect.com/science/article/pii/B9781416025894000115 |work=Diagnostic Surgical Pathology of the Head and Neck (Second Edition) |pages=839–881 |editor-last=Gnepp |editor-first=Douglas R. |access-date=2020-11-20 |place=Philadelphia |publisher=W.B. Saunders |language=en |doi=10.1016/b978-1-4160-2589-4.00011-5 |isbn=978-1-4160-2589-4 |last2=Pfaltz |first2=Madeleine|url-access=subscription }}{{Verify source|date=July 2023}}

Its superior belly divides the anterior triangle into an carotid triangle (above) and a muscular triangle (below).Human anatomy, Jacobs, Elsevier, 2008, page 189{{Verify source|date=July 2023}} Its superior belly serves as the most lateral member of the infrahyoid muscles, located lateral to both the sternothyroid muscles and the thyrohyoid muscles.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 102{{Verify source|date=July 2023}}

The tendon is related to the internal jugular vein and can be used as a landmark for this vein during surgery.{{Citation needed|date=July 2023}}

The omohyoid muscle may be doubled or completely absent in some people.{{Citation needed|date=November 2020}} Either belly may be doubled or absent.{{Cite book |last=Standring |first=Susan |url=https://www.worldcat.org/oclc/1201341621 |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |year=2020 |isbn=978-0-7020-7707-4 |edition=42nd |location=New York |pages=581 |oclc=1201341621}}

The inferior belly may be attached to the clavicle directly (rather than by fascia).{{Cite book |last=Standring |first=Susan |url=https://www.worldcat.org/oclc/1201341621 |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |year=2020 |isbn=978-0-7020-7707-4 |edition=42nd |location=New York |pages=581 |oclc=1201341621}}

The superior belly may be fused with the sternohyoid muscle.{{Cite book |last=Standring |first=Susan |url=https://www.worldcat.org/oclc/1201341621 |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |year=2020 |isbn=978-0-7020-7707-4 |edition=42nd |location=New York |pages=581 |oclc=1201341621}}

The muscle depresses the hyoid bone when the bone is in an elevated position.

A putative action of the muscle is tension of the inferior portion of deep cervical fascia to prevent soft tissues from collapsing inward into the upper airway during deep inspiration.

The name "omohyoid" derives from the Greek "omos" meaning shoulder, giving one of its attachments, and "hyoid", giving the other attachment – the hyoid bone.{{Citation needed|date=July 2023}}

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• {{SUNYAnatomyLabs|24|06|01|00}}
• {{SUNYAnatomyFigs|24|01|09}}
• {{NormanAnatomy|lesson6}}

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Category:Muscles of the head and neck