The hyoid bone is a very small and therefore mostly underestimated bone located below the tongue at the base of the mouth. The medical names are os hyoideum and hyoid, respectively.
What is the hyoid bone?
Located between the larynx and lower jaw, the hyoid bone is only about two to three centimeters long and curved in a U-shape. It is usually considered to be part of the cranial skeleton. However, this point is debatable because the hyoid bone is already located at the transition to the neck in the pharyngeal region. The hyoid bone is an unpaired bone that can be felt through the skin as well as visualized by standard imaging examination techniques, such as x-ray, ultrasound, or computed tomography. The integration of the hyoid bone into its environment is optimal, especially since it is fixed only with various muscles and ligaments in the area of the skull base. There is no connection to other bones and thus to the skeleton. Skeletal models are therefore often incomplete with regard to the hyoid bone. The complex interaction of the hyoid bone, the adjacent muscles and the surrounding body parts is the basis for error-free swallowing, breathing and speaking. The hyoid bone even has an influence on coughing and various movements.
Anatomy and structure
The hyoid bone is composed of a middle piece, the corpus ossis hyoidei, and four so-called hyoid horns. Two of the horns, medically cornu majus, point posteriorly and end with a small thickening. They form in the embryonic phase together with the middle piece from the cartilages of the third pharyngeal arch and are connected to the larynx. The two anterior horns, cornu minus, are somewhat smaller and arise from the second pharyngeal arch. They are connected to the temporal bone by the stylar process – an ossified connection found only in humans and other primates. The muscles surrounding the hyoid bone are divided into two groups, each containing outer and deeper muscles. While the suprahyal muscles (geniohyoideus muscle, mylohyoideus muscle, digastricus muscle, stylohyoideus muscle) are capable of pulling the hyoid bone upward, the infrahyal muscles (sternohyoideus muscle, omohyoideus muscle, thyrohyoideus muscle) enable the hyoid bone to be pulled downward. The muscles lead towards the tongue, throat as well as the jaw. Even connections to the chest and shoulder blades are present.
Function and tasks
Without the movements of the hyoid bone and the contractions of the muscles connected to it, the functions of speaking, breathing and also swallowing cannot be performed properly. Only through the hyoid bone are, for example, the targeted movements of the tongue possible. This is stabilized by the small curved bone and only then allows the formulation of words. The hyoid bone is supported by the larynx, which is connected to it by a flexible membrane through which the upper laryngeal artery also passes. In addition to the larynx, the trachea is also loosely attached to the hyoid bone. It can be closed or opened as needed. In doing so, muscles pull the hyoid bone along with the larynx upward during the swallowing process, pressing the laryngeal cap against the inside of the neck and closing the entrance to the larynx. Other muscle groups, in turn, subsequently pull the hyoid bone downward. Food is forced into the esophagus and breathing is released through the trachea. Consequently, simultaneous swallowing and breathing is not possible. However, if speaking is done in parallel, there is a risk that small pieces of food will touch the larynx and trachea, triggering a coughing impulse. But the hyoid muscles play a major role not only in swallowing. Among other things, they serve to open the jaw and chew through their connection to the floor of the mouth. In addition, as part of the neck muscles, they participate in the coordination of movement of the shoulders and neck area – a connection that is often neglected.
Diseases
Diseases of the hyoid bone itself are extremely rare. Only sporadically are inflammations or tumors observed on it. Occasionally, carcinomas of the thyroid gland extend through the hyoid bone to the tongue. Cysts, on the other hand, usually form only in its vicinity and do not affect this bone. The hyoid bone can also fracture due to the action of force.However, this requires a large amount of force, which can be achieved when a person is strangled or strangled. Since such pressure is usually applied involuntarily, the fracture of a hyoid bone is a topic mainly in forensic medicine. The force required for the fracture inevitably damages other parts of the neck, and thus a hyoid fracture is almost invariably diagnosed in dead people. On the other hand, there are complaints such as problems with breathing or poor posture of the body. They occur more often, but in many cases are not immediately associated with the hyoid bone and the adjacent muscles. One example is mandibular recession, in which the hyoid bone is anchored unusually loosely and is too far back. The result is a narrowing of the trachea, which leads to corresponding breathing problems. Although hyperextension of the head brings relief in breathing, it can also lead to tension, pain, migraine or poor posture. Tension in the hyoid muscles can also have far-reaching consequences. If their activity is restricted due to immobility, tense movements, a stiff neck or discomfort when swallowing appear.
