Thyroid Muscles: Anatomy, Function, and Related Conditions
Beyond the gland, a set of crucial muscles supports neck function. Learn how these structures relate to the thyroid, from daily actions to surgical considerations.
The neck houses the thyroid gland, a butterfly-shaped endocrine structure situated at the front of the neck. This region is a complex assembly of bones, cartilage, and soft tissues, including several muscles in close proximity to the thyroid gland. Understanding the arrangement and purpose of these surrounding muscles is helpful for appreciating the integrated nature of the neck’s structure.
Defining the Thyroid Muscles: Anatomy and Location
The term “thyroid muscles” is an informal descriptor for the muscles positioned directly around the thyroid gland. This primarily refers to the infrahyoid muscles, often called strap muscles due to their long, flat shape. This group consists of four pairs of muscles: the sternohyoid, sternothyroid, thyrohyoid, and omohyoid. These muscles are organized into a superficial layer, containing the sternohyoid and omohyoid, and a deep layer with the sternothyroid and thyrohyoid.
These muscles occupy the space between the hyoid bone in the upper neck and the upper chest. The sternothyroid muscle, for instance, lies over the anterior surface of the thyroid gland. The strap muscles are covered by the sternocleidomastoid, a large muscle that runs from behind the ear down to the collarbone and sternum. This layered arrangement creates a protective muscular casing around the larynx and thyroid gland.
Key Roles of the Thyroid Muscles
The muscles surrounding the thyroid gland are involved in swallowing and voice production. During swallowing (deglutition), the infrahyoid muscles depress the hyoid bone and the larynx. This movement helps close off the airway and allows food to pass into the esophagus.
For voice production (phonation), the sternothyroid depresses the larynx while the thyrohyoid can elevate it. These adjustments in the larynx’s vertical position, facilitated by the strap muscles, contribute to changes in vocal pitch and tone. By stabilizing this structure, they provide a foundation for the control required for speaking and singing.
Beyond their roles in swallowing and vocalization, the infrahyoid muscles also assist in stabilizing the neck. The omohyoid muscle has a specific function related to circulation; its attachment to the carotid sheath helps pull on the structure, which can lower pressure in the internal jugular vein and support blood return to the heart. Together, these muscles provide structural support and facilitate a range of motions for the head and neck.
Thyroid Muscles and Their Connection to the Thyroid Gland
The infrahyoid muscles are in direct contact with the thyroid gland, with the sternothyroid muscle covering much of its front surface. This proximity is significant during thyroid surgery, such as a thyroidectomy. To access the gland, surgeons must retract or sometimes cut the fascia connecting the sternohyoid and sternothyroid muscles.
Conditions affecting the thyroid gland can also impact these muscles. A significantly enlarged thyroid (goiter) or large thyroid nodules can press against the strap muscles. This physical compression may lead to feelings of tightness or pressure in the neck.
Common Conditions Affecting Thyroid Muscles
Issues can arise directly within the muscles near the thyroid gland. Muscle strain from overuse or holding an awkward posture can lead to localized pain and stiffness in the anterior neck. Stress and tension can also cause muscle spasms or myofascial pain, which involves tender points in the muscle tissue.
Symptoms of muscle dysfunction can mimic other conditions. Pain or difficulty swallowing (dysphagia) or voice changes like hoarseness may result from muscular problems. These symptoms occur when the muscles cannot properly coordinate movements for swallowing or stabilize the larynx for voice production.
Following thyroid surgery, manipulation of the strap muscles can cause temporary weakness, soreness, and difficulty swallowing. These symptoms resolve as the muscles heal. In rare cases, damage to the ansa cervicalis nerve during a procedure can lead to more persistent weakness or paralysis of the infrahyoid muscles, causing a hoarse voice and throat tightness.