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The hyoid bone is a U-shaped bone located in the anterior neck. It is the only bone in the human body that does not articulate with any other bone, instead being suspended by a network of muscles and ligaments. The hyoid bone is important for tongue movement, swallowing, breathing, and speech. The muscles attaching to the hyoid bone can be classified into two groups: the suprahyoid muscles, which are located superior to the hyoid bone and are involved in elevating it, and the infrahyoid muscles, which are located below the hyoid bone and depress it.
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What You'll Learn
Digastric muscle
The digastric muscle is a small paired muscle located in the anterior compartment of the neck. It is part of a group of muscles called the suprahyoid muscles, which also includes the mylohyoid, geniohyoid, and stylohyoid muscles. The digastric muscle has two parts: an anterior belly and a posterior belly, joined by an intermediate tendon. The muscle derives its name from the Greek word "dis" meaning double or twofold, and the Latin "gaster" meaning belly.
The anterior belly of the digastric muscle originates from the digastric fossa of the lower border of the mandible, near the midline close to the mandibular symphysis. This portion of the muscle extends postero-inferiorly from the mandible, joining with the intermediate tendon. The anterior belly is involved in jaw opening, chewing, and speech, as it raises the tongue base and hyoid bone, and depresses the mandible.
The posterior belly of the digastric muscle originates at the medial surface of the mastoid notch of the temporal bone. From here, it travels antero-inferiorly towards the hyoid bone, piercing the stylohyoid muscle before attaching to the intermediate tendon of the digastric muscle. The posterior belly is particularly involved in swallowing and chewing.
The two bellies of the digastric muscle have different embryological origins, with the anterior belly derived from the first brachial arch and the posterior belly from the second brachial arch. This results in different innervations for each belly. The submental artery, a branch of the facial artery, supplies blood to the anterior belly of the digastric muscle.
The digastric muscle is involved in complex jaw actions such as speaking, swallowing, chewing, and breathing. It also divides the anterior triangle of the neck into smaller triangles: the submandibular triangle (digastric triangle), carotid triangle, submental triangle (suprahyoid triangle), and inferior carotid triangle (muscular triangle).
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Mylohyoid muscle
The mylohyoid muscle, also known as diaphragma oris, is a flat and triangular-shaped muscle in the neck. It is one of the suprahyoid muscles, along with the digastric, geniohyoid, and stylohyoid muscles. The suprahyoid muscles connect the hyoid bone to the skull.
The mylohyoid muscle originates from the mylohyoid line of the mandible, which extends from the mandibular symphysis to the last molar tooth. The muscle forms the floor of the oral cavity of the mouth, or the oral diaphragm, and is essential for swallowing and speaking. It also reinforces the floor of the mouth, forming a contractile hammock to support the oral cavity base.
The mylohyoid muscle separates the sublingual space from the submandibular space, with these spaces communicating around the posterior border of the muscle. The submandibular gland wraps around the edges of the mylohyoid and is divided into superficial and deep lobes above and below the muscle.
The mylohyoid muscle elevates the hyoid bone and the tongue, which is important during swallowing and speaking. It also depresses the mandible when the hyoid bone is in a fixed position.
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Geniohyoid muscle
The geniohyoid muscle is a short, paired muscle that is part of the suprahyoid muscle group in the neck. It is named for its passage from the chin ("genio-" is a standard prefix for "chin") to the hyoid bone. It originates from the inferior mental spine, located on the posterior surface of the mandible near the lower part of the mandibular symphysis. From there, the muscle fibres radiate posteroinferiorly, close to the central line, and insert into the superior border of the body of the hyoid bone. The paired geniohyoid muscles, placed next to each other, meet in the midline of the mouth floor.
The geniohyoid muscle is innervated by the anterior ramus of spinal nerve C1, carried by the hypoglossal nerve. Its arterial supply comes from the sublingual branch of the lingual artery. The geniohyoid muscle is one of the muscles that constitute the floor of the oral cavity, along with the digastric, stylohyoid, and mylohyoid muscles. Its main function is to coordinate the movements of the floor of the mouth and the hyoid bone during swallowing and voice production.
The geniohyoid muscle elevates the hyoid bone and draws it anteriorly, causing the attached larynx and pharynx to move anterosuperiorly. This action dilates the upper airway, assisting respiration. During the first act of deglutition, when food is driven from the mouth into the pharynx, the geniohyoid muscle assists in depressing the mandible and pulling it inwards.
The hyoid bone is a small, U-shaped bone located in the anterior region of the neck. It is the only bone in the human body that does not directly articulate with any other bones. Instead, it is suspended by a complex network of muscles and ligaments that tether it to surrounding structures. The hyoid bone plays a pivotal role in functions such as swallowing, breathing, and speech, and is necessary for the production of a wide range of sounds.
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Infrahyoid muscles
The hyoid bone is a small, 'U'-shaped bone located in the anterior region of the neck. It is the only bone in the human body that does not directly articulate with any other bones. Instead, it is suspended by a complex network of muscles and ligaments.
The infrahyoid muscles are a group of four paired muscles located in the anterior part of the neck, inferior to the hyoid bone. They are also known as strap muscles due to their long and flat shape, similar to a belt or strap. These muscles include the omohyoid, sternothyroid, thyrohyoid, and sternohyoid. The omohyoid is comprised of two muscle bellies, which are connected by a muscular tendon. The superior belly arises from the hyoid bone, while the inferior belly arises from the scapula. The sternothyroid muscle is a wide muscle located underneath the sternohyoid in the deep plane of the neck. It arises from the manubrium of the sternum and attaches to the thyroid cartilage. The thyrohyoid is a short band of muscle, thought to be a continuation of the sternothyroid. It originates at the oblique line of thyroid cartilage and inserts onto the inferior border of the body and greater cornu of the hyoid bone. The sternohyoid muscle originates from the posterior surface of the manubrium of the sternum and the posterior surface of the medial end of the clavicle, inserting onto the inferior border of the body of the hyoid bone.
The infrahyoid muscles, along with the suprahyoid muscle group, are important for several functions related to speech, swallowing, and the movement of the larynx. They control the positioning of the hyoid bone and play an active role in depressing the hyoid bone during swallowing. The omohyoid has an additional function due to its attachment to the carotid sheath. By pulling the sheath, it maintains low pressure in the internal jugular vein, increasing blood return from the head to the superior vena cava.
The arterial supply to the infrahyoid muscles is via the superior and inferior thyroid arteries, with venous drainage via the corresponding veins. Each muscle is supplied by different nerves from the ansa cervicalis. Trauma in the region of the cervical spine can damage the ansa cervicalis, resulting in paresis or paralysis of the infrahyoid muscles, leading to clinical presentations such as swallowing difficulties, a hoarse voice, and throat tightness.
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Suprahyoid muscles
The hyoid bone is a U-shaped bone located in the anterior region of the neck. It is the only bone in the human body that does not articulate with any other bone, and is instead suspended by a network of muscles and ligaments. The hyoid bone plays a role in several physiological functions, including tongue movement, swallowing, breathing, and speech.
The muscles attaching to the hyoid bone can be classified into suprahyoid muscles and infrahyoid muscles. Suprahyoid muscles are located superior to the hyoid bone and are primarily involved in elevating it. They include the following:
Digastric Muscle: This muscle has an anterior and posterior belly, which are connected by an intermediate tendon. The tendon is suspended by a fibrous sling that attaches to the hyoid bone at the junction between the greater horn and the body. The digastric muscle elevates the hyoid bone and depresses the mandible.
Mylohyoid Muscle: The mylohyoid muscles originate from the mylohyoid line of the mandible and form the floor of the mouth. The anterior fibers insert into the mylohyoid raphe, while the posterior fibers insert into the lower anterior surface of the body of the hyoid bone.
Geniohyoid Muscle: This muscle originates from the inferior mental spine of the mandible and travels inferiorly to insert into the anterior surface of the body of the hyoid bone. It moves the hyoid bone upward and forward, widening the airway passage.
Stylohyoid Muscle: The stylohyoid muscle is a thin, long muscle that originates from the styloid process of the temporal bone and travels inferiorly. It attaches to the junction between the greater horn and body of the hyoid bone, retracting and elevating the bone.
These suprahyoid muscles facilitate chewing, swallowing, and phonation. They also assist in neck flexion and play a crucial role in airway management, as their dysfunction can contribute to obstructive sleep apnea.
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Frequently asked questions
The hyoid bone is a small, U-shaped bone located in the anterior region of the neck. It is the only bone in the human body that does not articulate with any other bone directly.
The hyoid bone provides attachment to the muscles of the floor of the mouth, the tongue, the larynx, the epiglottis, and the pharynx.
Suprahyoid muscles are located superior to the hyoid bone and are primarily involved in elevating it. They include the digastric, stylohyoid, mylohyoid, and geniohyoid muscles.
Infrahyoid muscles, also known as strap muscles, are located below the hyoid bone and primarily depress the bone. They include the thyrohyoid and omohyoid muscles.
In addition to muscles, the hyoid bone is also attached to ligaments such as the stylohyoid, thyrohyoid, and hyoepiglottic ligaments. It is connected to surrounding structures like the mandible, styloid processes of the temporal bone, sternum, and thyroid cartilage.
