Hyoid Bone Definition

The hyoid bone is the solitary bony component in the larynx; it is also the only bone in humans that does not connect with other bones. Rather than that, it binds to cartilage, muscles, and ligaments. As a result, it is commonly referred to as “free-floating.” Mastication (chewing), tongue movement, phonation, and swallowing all rely on it. Strangulation might be indicated by a fractured hyoid bone.

What is the Hyoid Bone?

The tongue bone, the hyoid bone, sometimes referred to as the hyoid bone, is a U-shaped or horseshoe-shaped bone. The Greeks named the upside-down letter U (upsilon) “hyodeides,” which is how the tongue bone earned its most well-known moniker.

A part of the hyoid-larynx complex is the lingual bone, which plays an important role in orofacial movement. Between the oropharynx on the upper side as well as the cartilaginous tracheal rings on the lower side, it helps to maintain the airway open.

Where is the Hyoid Bone Located?

The hyoid bone is located between the chin and the cartilage of the thyroid gland at the third or fourth cervical vertebra.

The cricoid cartilage is the first cartilage you can feel as you go up the neck’s midline from its base. The thyroid cartilage is above this, and the tongue bone is above the thyroid cartilage.

The hyoid bone is located just behind the submaxillary or digastric triangle, a prominent structure beneath the lower jaw (mandible).

Hyoid Bone Anatomy

The architecture of the hyoid bone is simple, but it serves as an attachment site for a variety of muscles. A part of the hyoid-larynx complex is the lingual bone, which includes the hyoid and its ligaments, as well as the thyroid, cricoid, and arytenoid cartilages and ligaments.

Because it has no junctions with other bones, the hyoid bone is unusual. The hyoid-larynx complex is held in place by muscles, ligaments, and surrounding cartilage, as well as ligaments of the temporal bones of the skull.

The left and right stylohyoid ligaments support the tongue bone from the ends of the left and right temporal bones’ styloid processes. Additionally, you can observe how the hyoid is attached to the tongue.

Hyoid Bone Parts

The body of the lingual bone is made up of two horns that give it its characteristic form.

The body is 2.5 cm in width and one centimetre in thickness. The anterior surface of the neck, which faces the front, is convex and sits somewhat forward and upward in a neutral posture. The body is divided into two parts by a vertical mid-line ridge.

The body’s posterior side, which faces the trachea, is concave and points slightly backward and downward in a neutral posture. The tongue bone is separated from the epiglottis soft tissue by a membrane known as the hyothyroid membrane.

The larger and smaller cornua are the two paired horns.

The bigger horns of the hyoid bone extend rearward and serve as a muscle attachment point, similar to the body. The stylohyloid ligament attaches to the hyoid bone’s smaller horns, which are shorter and stumpier. The hyoid is held in place by this ligament by the styloid processes of the temporal bones. The styloid processes may be seen in the figure below, which displays the rear of the skull and spine.

A clicking hyoid bone is an unusual occurrence. This term refers to an unpleasant hammering noise in the throat. The bigger horns’ tips connect with the cervical vertebra directly behind them, causing this. It might be unpleasant to swallow and move your neck. Photographs of a greater cornua excision while clicking hyoid bone surgery are included in this study.

Hyoid Bone Muscle Attachments

This bone serves as a point of attachment for two sets of muscles: suprahyoid (above the hyoid) and infrahyoid (below the hyoid).

The lingual bone is connected to the jaw, skull, and tongue by four pairs of suprahyoid muscles. When the suprahyoid muscles have their beginnings above the hyoid and insert at the hyoid, when they flex, the tongue bone is dragged upward. The following are the four muscles:

• Digastric muscle
• Stylohyoid muscle
• Mylohyoid muscle
• Geniohyoid muscle

When the digastric muscle engages while speaking, swallowing, or even breathing, the hyoid bone raises. The lower jaw will drop, opening the mouth if other muscles obstruct the hyoid’s upward migration.

The stylohyoid muscle, which arises from the temporal bone’s styloid process, also elevates the tongue bone as we begin to swallow.

The mylohyoid muscle lifts the lingual bone and tongue as we speak or swallow. It, like the digastric muscle, aids in mouth opening. Opening the mouth is caused by lowering the lower jaw, or mandible. It has the same dramatic effect as lowering the upper jaw, or maxilla, does not.

To open the airway, the geniohyoid muscle elevates the hyoid bone. It’s also involved in swallowing and opening the mouth.

From the hyoid bone to the shoulders, there are four sets of infrahyoid muscles. The lingual bone serves as the attachment site for these muscles, which have their beginnings at the base of the neck and shoulders, pulling the hyoid down.

• Muscle of the sternohyoid
• Muscle of the sternothyroid
• Muscle of the omohyoid
• Muscle of the thyrohyoid

The infrahyoid muscles draw the hyoid bone back down after the suprahyoid muscles raise it. The airway dilates when the hyoid is lifted.

The airway must be sealed when we swallow meals to prevent food particles from entering the lungs. When expanding the mouth to talk, eat, and to a lesser extent, for certain head motions, hyoid depression is also necessary.

Two muscles that are not included in the above-mentioned muscle groups originate from the tongue bone. The hyoglossus and middle pharyngeal constrictor muscles are referred to as the hyoglossus and middle pharyngeal constrictor muscles, respectively.

The hyoglossus depresses and pulls back the tongue, while the middle pharyngeal constrictor constricts around the food bolus entering the oropharynx, driving it down into the oesophagus.

Hyoid Bone Ligamentous Attachments

The lingual bone is connected to the thyroid cartilage by the thyrohyoid membrane, which is a ligament. The larger horns and the rear of the hyoid body are connected by this strong membrane that starts at the top of the thyroid cartilage.

The stylohyoid ligament originates from the temporal bone’s styloid process and extends to the hyoid bone’s lesser horn. As we’ve seen.

The hyoepiglottic ligament is the third ligament that joins the hyoid. This links the hyoid body’s top to the epiglottis’ front (anterior surface).

The epiglottis is a soft tissue flap that protects the airway by falling over the trachea as we swallow. Through the vocal chords, a breathing tube is placed and directed towards the lungs during endotracheal intubation.

Hyoid Bone Function

The tongue is held up by the hyoid bone from below, while the larynx is held in place by the hyoid bone from above.

The lingual bone plays a role in maintaining an open airway between the oropharynx and tracheal rings. When chewing (and swallowing), as well as when speaking, it is required.

Among the hyoid bone’s additional roles is its capacity to prevent regurgitation. It also aids with tongue control and has a small impact on head placement.

Hyoid Bone Fracture

Because this little bone is typically broken while manual (with the hands) and ligature (hanging/garotting) strangling, hyoid bone fractures are a common indication during forensic examinations. Blunt force trauma to the neck may potentially cause a hyoid fracture.

Manual strangulation is the most prevalent cause of a fractured hyoid, as stated on pages 5–7 of this University of Mississippi Medical Center article.

Lingual bone fractures affect around one-third of strangulation victims, and this form of fracture is more common among the elderly. The body and larger horns of the hyoid bone merge as we age, resulting in less give and a higher risk of these joints snapping. Ankylosis refers to the fusing of bone joints.

Serial murderers have been known to strangle their victims. This scholarly paper delves further into the disturbing repercussions of strangling.

During strangling, the larger horns get crushed against the third or fourth cervical vertebrae as they extend toward the rear of the neck. Due to the connection between the superior horns of the thyroid cartilage and the bigger horns of the hyoid, pressure on the thyroid may result in hyoid fractures and vice versa.

Hyoid Bone and Sleep Apnea

Obstructive sleep apnea syndrome (OSAS) is a persistent respiratory disease in which the throat contracts during sleep.

It’s easy to see why the tongue bone is important. It’s an attachment site for the suprahyoid and infrahyoid muscle groups, and it’s these muscles, together with oropharyngeal muscles, that maintain the airway open. Many neurological impulses go away as we sleep, which is especially visible in our muscles. People who have sleep paralysis are aware of how unresponsive their muscles become.

The upper airway closes in OSAS due to relaxed muscles and pressure from fatty tissue (OSAS is commonly linked with overweight people).

Obstructive sleep apnea is exacerbated by a hyoid posture. When the two hyoid muscle groups aren’t functioning together, pharyngeal collapse occurs.

OSAS is frequently treated with continuous positive airway pressure (CPAP), which involves forcing air into the airway under pressure. However, surgery is also an option for treating this chronic disease.

The hyoid bone is usually the focus of surgical therapy. Hyoidothyroidopexy, hyoid suspension, and hyoid myotomy are examples of sleep apnea surgery. The hyoid is stitched to the top section of the thyroid cartilage by the former. The hyoid bone is brought forward by securing it to the lower jaw (below). The second form of surgery (carried done with or without suspension) cuts into the hyoid muscles to allow more air to move through.

References

Nguyen J, Duong H. (Updated 2019). Anatomy, Head and Neck, Sternohyoid Muscle. Treasure Island (FL): StatPearls Publishing. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK547693/

Schünke M, Schulte E, Ross LM, Lamperti ED, Schumache U. (2006). Thieme Atlas of Anatomy: Neck and Internal Organs. Stuttgart, Thieme.

Dolinak D, Matshes E, Law E. (2005). Forensic Pathology: Principles and Practice. New York, Elsevier Academic Press.