Muscles of the Larynx

There are many muscles that either make up a certain part of the laryngeal structure inside the neck, or that sit adjacent to it and aid in its function:
- These muscles produce the movements of the larynx and its cartilages:
  - Thus enabling the proper air conduction, speech, movements of the epiglottis and airways protection
The muscles of the larynx are divided into two groups:
- Extrinsic muscles:
  - Which produce the movements of the hyoid bone
  - The extrinsic muscles of the larynx are those that are somehow attached to the hyoid bone:
    - Be it via origin or insertion and thus move the thyroid cartilage
  - These are the:
    - Infrahyoid:
      - The infrahyoid muscles are part of and attach to the lower larynx as well as the inferior aspect of the hyoid bone
      - This muscle group includes the:
        Sternohyoid
        Omohyoid
        Sternothyroid
        Thyrohyoid
      - These muscles work to lower the larynx and the hyoid bone
    - Suprahyoid muscles:
      - Are attached to the superior aspect of the hyoid bone
      - Function to fixate the hyoid bone as well as elevate it along with the larynx
      - These muscles include:
        Stylohyoid
        Digastric
        Mylohyoid
        Geniohyoid
      - The stylopharyngeus muscle is not attached directly to the hyoid bone:
        However it acts indirectly to elevate both the hyoid bone and the larynx
- Intrinsic muscles:
  - Which move the vocal cords in order to produce speech sounds
  - They are functionally divided into:
    - Adductors:
      - Lateral cricoarytenoid:
        Ailing from the arch of the cricoid cartilage, this muscle distally attaches itself to the muscular process of the arytenoid cartilage
        It acts as an adductor of the vocal folds
      - Transverse arytenoid
    - Abductors:
      - Posterior cricoarytenoid:
        The proximal attachment of this muscle is on the posterior surface of the lamina of the cricoid cartilage and its corresponding insertion point is on the muscular process of the arytenoid cartilage
        The recurrent laryngeal nerve innervates this muscle:
        As it does all the other intrinsic muscles of the larynx:
        With the exception of the cricothyroid muscle
        Its function is to abduct the vocal folds
    - Sphincters:
      - Transverse arytenoid:
        The arytenoid cartilage acts as a point of origin for both the transverse and oblique arytenoid muscles:
        Which run between the two arytenoid cartilages, as they distally attach to the opposing arytenoid cartilage
        Due to their points of attachment, they are able to close the intercartilaginous portion of the rima glottidis
      - Oblique arytenoid
      - Aryepiglottic
    - Muscles that tense the vocal cords:
      - Cricothyroid:
        This muscle originates on the anterolateral part of cricoid cartilage and inserts into the inferior border of the thyroid cartilage and its inferior horn
        It is innervated by the external branch of the superior laryngeal nerve
        Irrigation is by the superior and inferior thyroid arteries:
        As are all the intrinsic laryngeal muscles
        Upon contraction:
        It lengthens and tenses the vocal ligaments
    - Muscles that relax the vocal cords:
      - Thyroarytenoid:
        The thyroarytenoid muscle originates from the angle of thyroid cartilage and adjacent cricothyroid ligament
        It inserts into the anterolateral surface of arytenoid cartilage:
        Just as the posterior and lateral cricoarytenoid muscles do
        As for function, the muscle shortens and relaxes the vocal cords
      - Vocalis:
        The proximal attachment of the vocalis muscle is upon the vocal process of the arytenoid cartilage
        It inserts distally upon the vocal ligament and acts by tensing the anterior vocal ligament and relaxing the posterior vocal ligament