Omohyoid muscle

The Omohyoid muscle is a thin, elongated muscle located in the front of the neck. It is composed of two bellies separated by an intermediate tendon and is attached at one end to the scapula (shoulder blade) and at the other end to the hyoid bone. The Omohyoid muscle's main function is to depress the hyoid bone, which is a small, U-shaped bone located in the neck that serves as a point of attachment for several muscles involved in swallowing and speech.^[1] The Omohyoid muscle helps to anchor the hyoid bone in place, allowing it to function properly during these activities. The superior belly of the Omohyoid muscle is the most lateral member of the infrahyoid muscles, located lateral to both the sternothyroid muscles and the thyrohyoid muscles. It is an important muscle for maintaining proper posture and facilitating proper breathing and swallowing.^[2]

Structure

The Omohyoid muscle is a long, slender muscle that originates from the posterior border of the scapula (shoulder blade). It is composed of two main parts: the superior belly and the inferior belly.

• The superior belly is a thin, triangular muscle that arises from the posterior border of the scapula and inserts onto the hyoid bone.
• The inferior belly is a thicker, more oval-shaped muscle that arises from the posterior border of the scapula and inserts onto the hyoid bone and the thyrohyoid membrane.

The Omohyoid muscle is innervated by the ansa cervicalis, a branch of the cervical spinal nerves.^[8]It has a rich blood supply, with numerous branches of the superficial cervical artery and vein running through it. There are several variations of the Omohyoid muscle that can occur. These include the presence of additional bellies, the absence of one of the bellies, or the presence of additional tendinous bands. These variations are relatively rare and do not significantly impact the function of the muscle.

Location

The Omohyoid muscle is located in the neck, extending from the posterior border of the scapula to the hyoid bone. It lies deep to the Sternocleidomastoid muscle and the Trapezius muscle, and is partially covered by the Sternohyoid muscle.^[6] The Omohyoid muscle is located in the region of the neck known as the suprahyoid muscles, which are a group of muscles that attach to the hyoid bone and assist in swallowing and speech.^[5]

Function

Stabilizing the hyoid bone

The main function of the Omohyoid muscle is to stabilize the hyoid bone, which is a small, U-shaped bone located in the neck that serves as a point of attachment for several muscles involved in swallowing and speech.^[4] The Omohyoid muscle helps to anchor the hyoid bone in place, allowing it to function properly during these activities.

Breathing and swallowing

In addition to its role in stabilizing the hyoid bone, the Omohyoid muscle also assists in breathing and swallowing.^[2]When the Omohyoid muscle contracts, it helps to lift the hyoid bone and larynx (voice box), which can open up the airway and allow for easier breathing. It also helps to elevate the larynx during swallowing, allowing food and liquids to pass through the pharynx (throat) more easily.

Posture

The Omohyoid muscle also plays a role in posture and head movement. When it contracts, it helps to pull the head and neck forward, which can contribute to good posture. It also helps to rotate the head to the opposite side when contracting unilaterally.^[3]

Clinical Significance

Problems with the Omohyoid muscle can lead to various clinical issues. One common problem is the development of Omohyoid syndrome, which is characterized by pain and weakness in the neck and shoulder region due to irritation or compression of the Omohyoid muscle. This condition is often caused by the presence of a cervical rib, which is an extra rib that grows above the first rib and can compress the Omohyoid muscle. Another clinical issue that can arise with the Omohyoid muscle is difficulty swallowing or speaking. This can be caused by damage to the Omohyoid muscle or other suprahyoid muscles, which can result in weakness or paralysis of these muscles. This can make it difficult to lift the hyoid bone and larynx properly, leading to problems with swallowing and speaking. In addition to these clinical issues, the Omohyoid muscle can also be affected by a variety of injuries or conditions, including strains, sprains, and inflammation. These injuries can result in pain and weakness in the neck and shoulder region, and may require treatment such as rest, physical therapy, or medication.^[4]