The sternothyroid muscle is a muscle of the human skeletal system. It is located between the tongue and the larynx. Its function is to assist in the swallowing process.
What is the sternothyroid muscle?
The sternothyroid muscle is called the sternocleidomastoid cartilage muscle. It is a muscle that is part of the hyoid bone musculature. This is referred to as the infrahyal musculature. The sternothyroid muscle is a narrow muscle that pulls from the sternum to the upper part of the larynx. It is instrumental in the performance of the swallowing act in humans. As soon as the muscle fibers of the sternothyroid muscle contract, the hyoid bone moves downward. At the same time, the larynx also moves downward. This process occurs at the moment when the swallowing reflex kicks in. This clears the way to the stomach. This process is no longer subject to voluntary control, even if the preparations for the act of swallowing are controlled and planned.
Anatomy and structure
The sternothyroid muscle is a striated muscle. This means that the muscle fibers of the muscle have an arrangement in which they repeat periodically. This results in a certain pattern. It is formed by transverse striations. The sternothyroid muscle originates from the manubrium sterni. This is a part of the sternum. It is located cranially, at the top, and forms the widest part of the sternum. This is called the sternum in medicine. The sternum connects with the clavicle. The larynx is called the larynx. It consists of fibers as well as cartilage and is set in motion by various muscles. The larynx has a vertical shape and is enclosed all around by various layers of cartilage. These include the thyroid cartilage, the cricoid cartilage, the stellate cartilage and the epiglottis cartilage. The thyroid cartilage is called the cartilago thyreoidea. The sternothyroid muscle runs from the sternum below the sternohyoid muscle. Its path continues to the thyroid cartilage, which it sets in motion. The sternothyroid muscle is innervated by the ansa cervicalis. This is a nerve pathway composed of various fibers of the cervical plexus and spinal cord.
Function and tasks
The sternothyroid muscle, along with other muscles in the mouth and throat, is responsible for the functional activity of swallowing. During the act of swallowing, there is first an elevation of the pharynx and then a lowering. At the same time, the trachea is closed so that the fluids, food and saliva produced in the mouth can be passed directly into the esophagus and down to the stomach. The act of swallowing is considered very complex. Various muscles work in close cooperation with each other so that it can take place without errors. The process of swallowing is divided into a voluntary controlled process and an automatic process. Preparations, such as crushing the food or adding liquids, belong to the voluntary controlled process. They initiate the act of swallowing. In this process, the ingested substances are moved deep into the pharynx. Here, the functionality of the tongue plays an essential role. Once there, the swallowing reflex is automatically initiated. During this process, the trachea is closed and the base of the tongue is lifted. This pushes food, saliva and liquids deeper into the throat. So that they can then flow out, the hyoid bone lowers. At the same time, the larynx also lowers. The activity of the sternothyroid muscle ensures that the hyoid bone and the upper cartilage of the larynx are lowered. In this way, it makes a significant contribution to a well-functioning swallowing act.
Diseases
Diseases that have an effect on the activity of the sternothyroid muscle include all those whose symptoms have discomfort in the area of the mouth to the larynx. These can be inflammatory diseases, paralysis, swelling, tissue neoplasms, as well as infections. In the case of inflammation and infection, problems occur during the swallowing act. In the case of paralysis or spasm, the swallowing process cannot be performed. Swelling includes enlargement of the tonsils or lymph. They close the throat entrance and cause narrowing of the esophagus. Sleep disorders such as sleep apnea result in cessation of breathing.There is a spontaneous relaxation of the muscles while the person’s consciousness is not active. Neoplasms, such as edema or cysts in the entrance of the throat to the larynx, contribute to narrowing of the channel between the pharynx and upper larynx. The formation of a carcinoma significantly impairs the activity of the larynx. Accidents or falls involving the neck have an immense impact on the swallowing process and phonotonia. Since the larynx is surrounded by a cartilaginous framework, it does not have the necessary protection as soon as the throat is constricted from the outside. Throat constriction not only affects the act of swallowing. In addition, the air supply is restricted or suspended. In the event of an emergency or the rescue of a person, emergency oxygenation may be required in some cases. For this procedure, a tracheotomy is performed and intubated. Depending on the situation, this may result in injury to the cartilaginous structure of the larynx. In medicine, this is referred to as trauma. Trauma can also occur if a patient has to be intubated for a long period of time. In addition, anything that attacks the throat and pharynx is harmful. This includes smoking, as well as inhaling toxic gases.
