Sternocleidohyoid muscle: what it is, its characteristics and how it works

The human body has more than 650 muscles in total, which together make up 40-50% of the weight of a healthy adult.

If the muscular system has been extensively studied on several occasions, it should be noted that some researchers include in this device only muscles that contract voluntarily (skeletal). According to other authors, the smooth or involuntary musculature and the heart would also come under this system.

In any case (and despite organizational disagreements), the function of the musculature is clear and concise: to allow movement and permanence of the human being in a three-dimensional space and to make possible the functionality of internal systems. We’re not just talking about grabbing an object or pumping blood – did you know that, for example, a human needs the action of 12 facial muscles to smile?

Beyond running and jogging, musculature allows us to convey emotions, show disagreements, joy, and even speak and manifest ourselves as a species. From movement and speech, to pumping blood and stability in airspace, conceiving of life without muscles today would be an impossible task. Stay with us like we tell you all about an extremely unique muscle: the sternocleidohiodeo.

    What are Muscles?

    Before delving into the peculiarities of this muscle, it is necessary to lay the foundations that surround the subject. A muscle could be defined as a contractile organ that determines the shape and contour of our body and also has cells capable of lengthening along its axis of contraction.

    There are 3 types of muscle tissue, which in turn give rise to 3 major muscle variants. These are:

    • Skeletal muscle tissue (striated): voluntary and striated muscles. They are attached to the bones, so they shape the skeleton and allow movement.
    • Smooth muscle tissue: it is involuntary. These muscles take longer to contract than skeletal muscles, but they can stay in this position longer.
    • Heart muscle tissue: found in the heart. Its contractions, rhythmic and strong, expel the blood of this organ while beating.

    We have a minimum of 650 muscles that make up our body, All volunteers (skeletal). If one begins to explain smooth and heart muscles, this figure easily rises to 840 muscles in total. Of course, we are moving in significant numbers.

    What is the sternocleidohyoid muscle?

    The muscle that belongs to us today belongs to the skeletal muscle group, that is to say the voluntary striated muscles of the muscular apparatus. It is the most superficial of the muscles of the infrahyoid region (Under the hyoid bone, located at the front of the neck and under the tongue) the joint function is to flex the head and allow movement of the larynx during speech, among other things.

    This muscle is characterized by a curved shape that is distributed on both sides of the neck, about 20 millimeters wide and fleshy in nature. We dissect each of its peculiarities in the following lines.

    1. Origin

    The sternocleidohyoid muscle originates from a tendon that is inserted into 4 different structures. These are the posterior edge of the clavicle (connecting the sternum bone to the scapula), the posterior surface of the sternoclavicular ligament, the lateral half of the sternum grip, the bone of the central and anterior thorax) and the first cartilage. costal (which joins the first ribs with the sternum).

    2. Insertions

    Its anatomical course is “up”, and towards the center to the inferior border of the hyoid bone.. To do this, it is inserted on the upper surface of the posterior edge of the clavicle, in the posterior surface of the sternoclavicular ligament, in the lateral half of the manubrium sternal and in the first costal cartilage. It should be noted that its trajectory towards the hyoid bone is not entirely rectilinear, the neck nut being interposed between the lower insertion point and the bone already mentioned.

      3. Innervation

      Its innervation comes from the handle of the hypoglossus, the junction of the fibers of the C1-C2-C3 roots of the cervical plexus. This nerve structure primarily controls the motor functions of the neck. The contraction of the sternocleidohyoid muscle, by means of nerve signals from this plexus, causes the descent of the hyoid bone (In which it is inserted in its last section).

      4. Relations

      As mentioned above, the sternocleidohyoid muscle is part of the group of the infrahyoid musculature, located below the hyoid bone. These muscles attach to the bone and cause it to descend by contractions, which is essential for phonation and swallowing., Among others. Some of the muscles that are related to what attracts us are:

      • Homohyoid muscle: digastric muscle which acts as a depressant of the hyoid bone and as a tensor of the middle cervical fascia.
      • Sternothyroid muscle: It is ribbon-shaped, much like the sternocleidohyoid. Its main function is to lower the larynx.
      • Thyroid muscle: short and quadrilateral, this muscle also promotes the descent of the hyoid bone with its contraction.

      5. Blood supply

      The sternocleidohyoid muscle, like all human tissue, it requires blood flow so that your cells can receive oxygen and nutrients, among other things. The lingual artery and the upper thyroid are responsible for it.

      Before the lingual artery enters the tissue of the tongue (its final destination), it issues a hyoid branch that follows the upper edge of the hyoid bone. Thus, it gives off a series of ramifications that nourish the aforementioned muscles.

      Functions of the sternocleidohyoid muscle

      The anterior part of the neck contains a number of structures vital for the development and survival of the human species.. The muscles involved (including the sternocleidohyoid) are responsible for carrying out head and neck movements, but also play essential functions in processes such as facilitating swallowing and phonation (speaking in humans).

      In addition to producing the descent of the hyoid bone when contracted, the infrahyoid muscles act as protectors of the trachea, the esophagus, the vasculature of the region and the thyroid glandss (which produce parathyroid hormone, which modulates the amount of circulating calcium).

      Above them is neck fat, a major absorber of mechanical damage that could seriously compromise the speech, respiratory and swallowing systems. Finally, above this fat is the skin of the neck, the first barrier that prevents the entry of pathogens.

      The role of the sternocleidohyoid in swallowing

      Finally, we will explore the mechanism by which the sternocleidohyoid facilitates swallowing in our species.

      The suprahyoid muscles elevate the hyoid bone (and therefore the larynx) with its contraction, an activity produced by the act of swallowing. This action closes the airways, preventing food from entering the wrong places.. Once food has passed from the pharynx to the esophagus, the sternocleidohyoid muscle helps reopen the laryngeal cavity (by lowering the hyoid and larynx), which allows air to flow back to the lungs. Without a structure as small and simple as this muscle, the process of breathing and swallowing in humans would surely be much more difficult.

      summary

      Spaces like this emphasize that even the smallest muscle and even the least ‘relevant’ bone play a vital role in the physiology and maintenance of the human body over time. Thanks to the sternocleidohideo muscle (next to others), the descent of the hyoid bone takes place, a process essential for swallowing, sound production and breathing, among others.

      Bibliographical references:

      • Alvarado, EAC and Girón, MDCT (2017). Study of the cadaver of the submandibular triangle. Mexican Journal of Stomatology, 3 (2), 104-110.
      • Barton Jr, FE, Spicer, TE and Byrd, HS (1983). Reconstruction of the head and neck with myocutaneous latissimus dorsi colpa: anatomical observations and report of 60 cases. Plastic and Reconstructive Surgery, 71 (2), 199-204.
      • Costache, A., Dumitru, M., Anghel, I., Cergan, R., Anghel, AG i Sarafoleanu, C. (2015). Ultrasound anatomy of the head and neck – a picture for the ENT specialist. Medical ultrasound, 17 (1), 104-108.
      • González, S., Figueroa, L., & Marín, G. Topographic anatomy of the head and neck.
      • Khan, YS and Bordoni, B. (2020). Anatomy, head and neck, suprahyoid muscle. StatPearls [Internet].
      • Sternocleidohyoid muscle, dolopedic. Collected February 15 from https://dolopedia.com/articulo/musculo-esternocleidohioideo#.YCosjWhKjIU
      • Prades, JM and Chardon, S. (2000). Anatomy and physiology of the trachea. EMC-Otolaryngology, 29 (1), 1-12.
      • Sternohyoid muscle, Radiopedia. Retrieved February 15 from https://www.kenhub.com/en/library/anatomy/sternohyoid-muscle
      • Steroid Muscle: Want More Info? Kenhub. Retrieved February 15 from https://www.kenhub.com/en/library/anatomy/sternohyoid-muscle
      • Trotoux, J. (2001). Access routes of the cervical esophagus. CEM General Surgery, 1 (1), 1-4.

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