Logan Steele
The hyoid bone is suspended from the cranium by the posterior suprahyoid muscles and from the jaw by the anterior suprahyoid muscles. There are four suprahyoid muscles: the digastric, stylohyoid, mylohyoid, and geniohyoid. These muscles all act to elevate the hyoid bone, an action involved in swallowing. The stylohyoid elevates and retracts the hyoid bone, elongating the floor of the mouth during swallowing. The mylohyoid elevates the hyoid bone, tenses the floor of the mouth, and supports the floor of the oral cavity. The geniohyoid pulls the hyoid bone anterosuperiorly, shortening the floor of the mouth and widening the pharynx during swallowing. The digastric is composed of two muscular bellies, which contract and pull upward on the hyoid bone.
| Characteristics | Values |
|---|---|
| Muscles that elevate the hyoid bone | Digastric, stylohyoid, mylohyoid, and geniohyoid |
| Number of muscles that elevate the hyoid bone | Four |
| Location of the muscles | Above the hyoid bone in the neck |
| Function | Involved in swallowing and mastication |
| Arterial supply to these muscles | Branches of the facial artery, occipital artery, and lingual artery |
| Innervation | Inferior alveolar nerve, a branch of the mandibular nerve |
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What You'll Learn
Digastric
The digastric muscle is a suprahyoid muscle located in the anterior region of the neck. It is composed of two muscular bellies: an anterior belly and a posterior belly, which are joined by an intermediate tendon. The tendon passes through a connective tissue loop attached to the hyoid bone. The digastric muscle is involved in complex jaw actions such as speaking, swallowing, chewing, and breathing.
The anterior belly of the digastric muscle originates in the digastric fossa on the inner surface of the mandibular body, extending downward and backward. It receives motor innervation from the mylohyoid nerve, a branch of the inferior alveolar nerve. The posterior belly, on the other hand, originates in the mastoid notch on the medial side of the mastoid process of the temporal bone, sloping downward and forward. The posterior belly is supplied by the digastric branch of the facial nerve and is particularly important in swallowing and chewing.
When the two bellies of the digastric muscle contract, they work together to elevate the hyoid bone. However, if the hyoid is fixed in place by the infrahyoid muscles, the digastric muscle instead acts to depress the mandible, opening the mouth for actions such as yawning or taking a large bite.
Variations in the structure of the digastric muscle have been observed in some cases, particularly in the anterior belly. These variations are important to consider during surgical procedures in the anterior region of the neck.
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Stylohyoid
The stylohyoid is a slender, suprahyoid muscle that originates from the styloid process of the temporal bone and inserts onto the hyoid bone. It is one of four suprahyoid muscles, the others being the mylohyoid, geniohyoid, and digastric muscles. The stylohyoid muscle is located in the anterior triangle of the neck, superior to the hyoid bone.
The stylohyoid muscle is innervated by the stylohyoid branch of the facial nerve (Cranial nerve 7). It receives arterial supply from branches of the facial, occipital, and posterior auricular arteries, which are large branches of the external carotid artery. The internal jugular vein is responsible for draining venous blood from the stylohyoid muscle.
The stylohyoid muscle acts to elevate and retract the hyoid bone, drawing it upwards, backwards, and superiorly. This action elongates the floor of the mouth, facilitating tongue retraction, which is important during swallowing. The stylohyoid also helps to keep the pharynx open during inspiration by tensing the floor of the mouth.
The stylohyoid muscle is highly variable, and it may be absent or doubled in certain individuals. It is situated anterosuperior to the posterior belly of the digastric muscle and may insert suprahyoid or infrahyoid muscles.
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Mylohyoid
The mylohyoid muscle is a flat, thin, and triangular-shaped muscle that forms the floor of the oral cavity of the mouth. It is one of the four suprahyoid muscles, along with the digastric, stylohyoid, and geniohyoid muscles. These muscles are located above the hyoid bone in the neck and are all pharyngeal muscles, except for the geniohyoid.
The mylohyoid muscle originates from the mylohyoid line, which is located on the inner surface of the mandible near the molars of the lower jaw. It then continues along the entire inner mandibular rim. The mylohyoid muscles meet at a median tendon called the mylohyoid raphe, which might be absent in some individuals. In such cases, the mylohyoid muscle fibres either blend with the anterior belly of the digastric muscle or fuse with each other.
The mylohyoid muscle functions to elevate the hyoid bone and the floor of the mouth, particularly during swallowing and speaking. It also depresses the mandible when the hyoid bone is in a fixed position. This action aids in deglutition, or swallowing, by pressing the tongue against the hard palate and pushing food towards the pharynx. Additionally, the mylohyoid muscle works with the infrahyoid muscle to guide the position of the hyoid bone.
The mylohyoid muscle is supplied by the mylohyoid nerve, a branch of the inferior alveolar nerve, which in turn arises from the mandibular nerve. The blood supply to the mylohyoid muscle is provided by the mylohyoid artery, a branch of the inferior alveolar artery, which originates from the internal maxillary artery.
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Geniohyoid
The geniohyoid muscle is a short, paired muscle that belongs to the suprahyoid muscle group of the neck. It is a narrow, short muscle that arises from the inferior mental spine, on the back of the mandibular symphysis, and runs backward and slightly downward, to be inserted into the anterior surface of the body of the hyoid bone. The geniohyoid muscle is innervated by the anterior ramus of spinal nerve C1, carried by the hypoglossal nerve.
The geniohyoid is one of four suprahyoid muscles, along with the digastric, stylohyoid, and mylohyoid muscles. These muscles are all pharyngeal muscles, with the exception of the geniohyoid. Together, they constitute the floor of the oral cavity. The main function of the geniohyoid muscle is to elevate the hyoid bone and draw it forward, dilating the upper airway and assisting respiration. This movement also assists in swallowing, widening the pharynx to receive food.
The hyoid bone is suspended from the cranium, above and behind, by the posterior suprahyoid muscles (stylohyoid and the posterior belly of the digastric). From the symphyseal region of the jaw in front, it is suspended by the anterior suprahyoid muscles, including the geniohyoid. The geniohyoid muscle pulls the hyoid bone anterosuperiorly, shortening the floor of the mouth and widening the pharynx during swallowing. This movement also assists in voice production by the vocal cords.
The geniohyoid muscle is involved in the first act of deglutition, when food is driven from the mouth into the pharynx. During this process, the hyoid bone and tongue are carried upward and forward by the anterior bellies of the digastrici, the mylohyoidei, and the geniohyoidei. If the hyoid bone is fixed by other muscles, the geniohyoid muscle assists in depressing the mandible and pulling it inwards, helping to open the mouth.
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Anterior and posterior suprahyoids and infrahyoids
The suprahyoid muscles are a group of four muscles located above the hyoid bone in the neck. They are the digastric, stylohyoid, mylohyoid, and geniohyoid muscles. They are all pharyngeal muscles, except for the geniohyoid muscle. The digastric muscle consists of two parts, or bellies, separated by an intermediate tendon. The anterior belly originates from the digastric fossa of the mandible, while the posterior belly originates from the mastoid notch of the temporal bone. When the two bellies contract, they pull upward on the hyoid bone. However, if the hyoid is fixed from below, the digastric assists in extreme opening of the mouth, such as yawning or taking a large bite. The mylohyoid elevates the hyoid bone and tenses the floor of the mouth. The geniohyoid pulls the hyoid bone anterosuperiorly, shortening the floor of the mouth and widening the pharynx during swallowing. The stylohyoid elevates and retracts the hyoid bone, elongating the floor of the mouth during swallowing.
The infrahyoid muscles, or strap muscles, are a group of four pairs of muscles in the anterior (frontal) part of the neck, located below the hyoid bone. They are the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. These muscles function to elevate and depress the hyoid bone and larynx during swallowing and speech. 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 hyoid bone. The thyrohyoid muscle constitutes the continuation of the sternothyroid, originating at the oblique line of thyroid cartilage and inserting on the inferior border of the hyoid bone.
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Frequently asked questions
The four muscles that elevate the hyoid bone are the digastric, stylohyoid, mylohyoid, and geniohyoid.
The digastric is comprised of two muscular bellies that are connected by a tendon. When the two bellies contract, they pull upward on the hyoid bone.
The stylohyoid muscle elevates and retracts the hyoid bone, elongating the floor of the mouth during swallowing.
The mylohyoid is a broad, triangular-shaped muscle that forms the floor of the oral cavity and supports the floor of the mouth. It elevates the hyoid bone and tenses the floor of the mouth.
The geniohyoid is located on either side of the midline of the neck, deep to the mylohyoid muscle. It pulls the hyoid bone anterosuperiorly, shortening the floor of the mouth and widening the pharynx during swallowing.
