Logan Steele
The strap muscles, also known as the infrahyoid muscles, are composed of four paired muscles: the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid. These muscles are located in the anterior part of the neck, below the hyoid bone, and are involved in movements of the hyoid bone and thyroid cartilage during vocalization, swallowing, and mastication. They are responsible for depressing the hyoid during swallowing and play an active role in the movement of the larynx.
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Infrahyoid muscles and their role in swallowing
The infrahyoid muscles, also known as the "strap muscles", are composed of four paired muscles: the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid. They are located inferiorly to the hyoid bone in the anterior part of the neck. These muscles are involved in movements of the hyoid bone and thyroid cartilage during vocalization, swallowing, and mastication.
The infrahyoid muscles lie in two planes: the superficial plane, which includes the omohyoid and sternohyoid muscles, and the deep plane, which includes the sternothyroid and thyrohyoid muscles. The arterial supply to these muscles is via the superior and inferior thyroid arteries, with venous drainage via the corresponding veins.
The infrahyoid muscles play an important role in swallowing by controlling the positioning of the larynx and hyoid bone. The omohyoid, sternohyoid, and thyrohyoid muscles act to depress the hyoid bone, while the thyrohyoid elevates the larynx, and the sternothyroid depresses it. The infrahyoid muscles also support the opening of the upper oesophageal sphincter by moving the hyoid bone anteriorly.
Dysphagia, or difficulty swallowing, may result from various problems such as neurological impairment and physiological and anatomical derangements in any region from the mouth to the oesophagus, including the muscles involved in swallowing. Infrahyoid muscle paralysis can also lead to swallowing difficulties, as well as a hoarse voice and throat tightness. This paralysis typically occurs due to trauma to the cervical spine, resulting in damage to the ansa cervicalis.
Several exercises have been introduced to strengthen the muscles involved in swallowing, such as the Shaker exercise, tongue press exercise, chin tuck against resistance (CTAR) exercise, and submandibular push exercise. These exercises have been studied for their effectiveness in inducing selective supra- and infrahyoid muscle contractions using surface electromyography (EMG).
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The four paired muscles that make up the strap muscles
The strap muscles, also known as the infrahyoid muscles, are composed of four paired muscles: the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid. These muscles are located in the anterior part of the neck, below the hyoid bone, and are responsible for depressing the hyoid during functions such as swallowing and vocalization.
The sternohyoid is the most superficial of all the infrahyoid muscles. It originates from the posterior surface of the manubrium of the sternum and the posterior surface of the medial end of the clavicle, inserting on the inferior border of the body of the hyoid bone. Like the omohyoid and sternothyroid, the sternohyoid is innervated by the ansa cervicalis (C1-C3), arising from the cervical plexus. It receives its blood supply from branches of the superior thyroid artery.
The sternothyroid is the only hyoid muscle that does not directly attach to the hyoid bone. It originates from the posterior surface of the manubrium of the sternum and the costal cartilage of rib 1, inserting on the oblique line of thyroid cartilage. The sternothyroid is innervated by the ansa cervicalis (C1-C3) and supplied by the superior thyroid and lingual arteries.
The omohyoid is a thin, narrow strap that lies anterior to the other strap muscles and the thyroid gland. It is composed of two bellies (superior and inferior) united at an angle by an intermediate tendon. The superior belly arises from the hyoid bone, while the inferior belly originates at the superior border of the scapula. The omohyoid is innervated by the superior ramus of the ansa cervicalis and the hypoglossal nerve. It is supplied by the superior thyroid and lingual arteries.
The thyrohyoid is a small, quadrilateral muscle that may be considered an upward continuation of the sternothyroid. It attaches to the lower border of the greater cornu and the adjacent part of the body of the hyoid bone. The thyrohyoid is innervated by fibres of the first cervical spinal nerve and branches of the hypoglossal nerve. It is supplied by the superior thyroid and lingual arteries.
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The deep and superficial layers of the strap muscles
The strap muscles, also known as the infrahyoid muscles, are composed of four paired muscles: the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid. These muscles are located below the hyoid bone on the anterolateral surface of the thyroid gland and play a role in movements of the hyoid bone and thyroid cartilage during vocalization, swallowing, and mastication.
The infrahyoid muscles can be divided into two layers: the superficial layer and the deep layer. The superficial layer is composed of the sternohyoid and the omohyoid muscles, while the deep layer consists of the sternothyroid and the thyrohyoid muscles.
The sternohyoid muscle is part of the superficial layer of the strap muscles. It receives its supply from branches of the superior thyroid artery. The sternohyoid muscle is involved in depressing the hyoid bone and plays a role in swallowing and phonation.
The omohyoid muscle is also part of the superficial layer and is found deep within the sternocleidomastoid muscle. It consists of two bellies, superior and inferior, united by an intermediate tendon. The omohyoid muscle is involved in depressing the hyoid bone and ensuring proper venous blood return through its attachment to the carotid sheath.
The deep layer of the strap muscles consists of the sternothyroid and the thyrohyoid muscles. The sternothyroid muscle is attached to the thyroid cartilage and supports the superior pole of the thyroid gland. It is involved in depressing the larynx and the hyoid bone. The thyrohyoid muscle, on the other hand, elevates the larynx.
Together, the infrahyoid muscles play an important role in swallowing and phonation due to their ability to move and position the larynx. They are ensheathed by the middle layer of the deep cervical fascia, contributing to one of the deep fascial compartments of the neck.
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The function of the omohyoid muscle
The omohyoid muscle is one of the four paired infrahyoid or strap muscles. It is a thin, narrow strap located in the neck, deep in the sternocleidomastoid. The omohyoid muscle consists of two bellies (superior and inferior) connected by an intermediate tendon. The superior belly is attached to the hyoid bone, while the inferior belly is attached to the scapula. The tendon is anchored to the clavicle and first rib by a band of deep cervical fascia.
The omohyoid muscle is innervated by the ansa cervicalis of the cervical plexus, with the superior belly innervated by the superior root of ansa cervicalis and the inferior belly innervated by the ansa cervicalis itself. The muscle is supplied by the superior thyroid artery (a branch of the external carotid artery) and the inferior thyroid artery (a branch of the thyrocervical trunk).
The omohyoid muscle has several important functions. Firstly, it depresses the hyoid bone, especially when it is in an elevated position. This action is crucial for swallowing and phonation, as it helps with the movement and positioning of the larynx. Additionally, the omohyoid muscle tenses the lower part of the deep cervical fascia during prolonged inspiration, preventing the soft tissues from collapsing inward into the upper airway.
Furthermore, the omohyoid muscle plays a role in venous blood return. By pulling on the carotid sheath, it maintains a low-pressure system in the internal jugular vein, leading to increased blood return to the superior vena cava. The intermediate tendon of the omohyoid muscle also overlies and tenses the cervical fascia, ensuring the patency of the internal jugular vein.
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The importance of the strap muscles for speech and vocalization
The strap muscles, also known as the infrahyoid muscles, are composed of four paired muscles: the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid. These muscles are located in the anterior part of the neck, below the hyoid bone, and are responsible for several functions related to speech, swallowing, and the movement of the larynx.
The infrahyoid muscles play a crucial role in controlling the positioning of the hyoid bone and the movement of the larynx, which is essential for speech and vocalization. The hyoid bone is a small, U-shaped bone located in the anterior neck, just below the mouth. It serves as an attachment site for the muscles of the tongue, soft palate, and pharynx, and plays a crucial role in tongue movement and swallowing.
The thyrohyoid muscle, one of the strap muscles, elevates the larynx, while the sternothyroid depresses it. The omohyoid muscle, another strap muscle, depresses the hyoid bone and also has a function in ensuring proper venous blood return through its attachment to the carotid sheath. By pulling on the carotid sheath, the omohyoid maintains a low-pressure system in the internal jugular vein, leading to increased blood return to the superior vena cava. This action is important for vocal cord hydration and lubrication, as well as overall vocal health.
In addition to their role in speech and vocalization, the strap muscles also work together during the act of swallowing. All of the infrahyoid muscles, except the sternothyroid, depress the hyoid bone during swallowing. This movement helps to facilitate the passage of food and liquid through the pharynx and into the oesophagus.
Damage to the strap muscles, or the nerves that innervate them, can lead to difficulties in swallowing, hoarseness of the voice, or throat tightness. This can occur as a result of trauma to the cervical spine, which may cause paresis or paralysis of the infrahyoid muscles.
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Frequently asked questions
The strap muscles, also known as the infrahyoid muscles, are a group of four paired muscles in the anterior neck below the hyoid bone. They are responsible for depressing the hyoid during functions like swallowing and the movement of the larynx.
The four paired muscles that make up the strap muscles are the sternohyoid, the sternothyroid, the omohyoid, and the thyrohyoid.
The name "strap muscles" comes from their long and flat shape, similar to a belt or strap.
