Sternohyoid Muscle: Structure, Function & Diseases

The sternohyoid muscle is a muscle that is part of the human skeletal musculature. Its path runs from the chin down to the sternum. It belongs to the hyoid muscles.

What is the sternohyoid muscle?

The sternohyoid muscle is called the sterno hyoid muscle. Its shape is narrow and its pathway runs vertically along the neck. During the act of swallowing, it pulls the hyoid bone downward. This clears the way for ingested food and nutrition to reach the stomach. It is a bilateral muscle that runs along the outside of the neck. In the anterior middle of the neck, the two cords are connected by connective tissue. The sternohyoid muscle is instrumental in carrying out a smooth swallowing process. As soon as it contracts, the hyoid bone moves and opens the way into the esophagus. This occurs with the onset of the swallowing reflex. The hyoid bone is fixed to the base of the skull. This is done by ligaments and the muscles that innervate the hyoid bone. In this way, it acquires a rocking function. On the lower side are the larynx and the trachea. Thus, the hyoid bone is in a direct connection with processes such as phonotonia, breathing, opening of the jaw, swallowing and coughing. The hyoid bone is a small curved bone below the tongue.

Anatomy and structure

The sternohyoid muscle is one of the striated muscles in humans. Its muscle fibers are arranged in a pattern and periodically repeating. This results in the formation of transverse striations. It is a slender muscle and one of four muscles assigned to the lower hyoid musculature. They include the omohyoideus muscle, the sternohyoideus muscle, the sternothyroideus muscle, and the thyrohyoideus muscle. The path of the sternohyoid muscle begins at the posterior aspect of the sternum. This is referred to by physicians as the manubrium sterni. There, the sternohyoid muscle finds its origin at the end of the clavicle, the collarbone. It pulls cranially to the lower edge of the hyoid bone. This is the os hyoidem. Viewed externally, the sternohyoid muscle runs vertically between the sternum to the chin. The sternohyoid muscle is supplied by nerve fibers from the ansa cervicalis profunda. This is a loop of nerves formed from branches of the nerve plexus. The nerve plexus is called the cervical plexus.

Function and tasks

The sternohyoid muscle has two major functions. Together with various other muscles in the mouth and throat, the sternohyoid muscle is involved in the very complex act of swallowing in the human organism. This is divided into different mechanisms. The first is the controlled as well as voluntary part. This includes the ingestion of food and liquids. This is consciously controlled. After grinding the food, it passes from the oral cavity to the pharynx via the tongue. There, voluntary control turns into an automatic process that can no longer be regulated. A swallowing reflex occurs. This transports the ingested substances from the pharynx into the esophagus. During this process, the trachea must be closed. Only then is it guaranteed that no food, liquids or saliva can pass through the esophagus into the stomach. Within the swallowing reflex, various muscles work together in a matter of seconds. The sternohyoid muscle is responsible for moving the hyoid bone downward. It belongs to the infrahyoid musculature. This means that it belongs to the lower hyoid muscles. The suprahyal musculature is to be distinguished from it. This is assigned to the upper hyoid musculature. Their task, in addition to the act of swallowing, is to support the opening of the jaw. Once the suprahyal musculature is active, the sternohyoid muscle immobilizes the hyoid bone. This is the second task of the sternohyoid muscle.

Diseases

There are several diseases that have an effect on the functional performance of the sternohyoid muscle. Virtually any ailment of the pharynx and upper neck can result in discomfort during the act of swallowing. In everyday life, scalding and burning can occur when drinks or food that are too hot are ingested in the mouth up to the throat. The mucous membranes are attacked by this and in severe cases vesicles form.Defects in the mucous membranes cause swallowing difficulties. In addition, they have an influence on phonation. The most common diseases associated with the sternohyoid muscle are inflammation and infarction. Both are associated with limitations of the swallowing act. Enlargement of the lymph or tonsils, such as with angina, results in narrowing of the cervical inlet. The swallowing process is more difficult and often associated with a sensation of pain. Paralysis or damage to the nerve fibers from the ansa cervicalis profunda result in the sternohyoid muscle not being innervated. It also shows signs of paralysis. If there is neoplasm of the tissue due to edema, cysts or carcinoma, this also results in narrowing of the esophagus. The channel between the pharynx and the upper part of the larynx is no longer clear, leading to discomfort during the act of swallowing. The larynx is completely enclosed by various cartilages. These are easily palpable from the outside of the neck. Cartilage is not as stable as bone. Therefore, external damage due to accidents or falls can result in parts of the cartilage being injured. Since the larynx as a whole is involved in the act of swallowing and voice production, direct effects are expected.