Anatomy and Physiology

Muscles of the Swallow, Action, Innervation, and Clinical Relevance

Muscles of the lips and face are a complex orientation of fibers that act in a synergistic action to generate precise movements of not only mastication and swallowing, but also facial expression and speech production. The muscles of the lips and face and cheeks are responsible for lip seal and oral containment (McFarland, 2015; Vandaele, Perlman & Cassell, 1995).

Muscles of the Tongue

The tongue is composed of (and controlled by) the following two groups of muscles:

• Intrinsic lingual muscles have their origin inside the tongue, and are responsible for adjustments in tongue form and position. These muscles help to shape and move the bolus posteriorly.

• Extrinsic lingual muscles allow the tongue to move forward, back, up, down, and laterally. These muscles help with tongue position to assist in moving the bolus posteriorly (McFarland, 2015; Vandaele, Perlman & Cassell, 1995).

Muscles of the Soft Palate

The velum is a posterior extension of the hard palate. These muscles work together to eliminate nasal regurgitation, and facilitate posterior oral containment (McFarland, 2015; Vandaele, Perlman, & Cassell, 1995).

Extrinsic Muscles of the Larynx

Extrinsic laryngeal muscles influence laryngeal position and movement and are classified by whether they are located above or below the hyoid bone. Generally speaking, suprahyoid muscles are sometimes classified as laryngeal elevators; conversely, infrahyoid muscles are sometimes classified as laryngeal depressors. The suprahyoid muscles also assist in elevation and the superior-anterior movement of the hyolaryngeal complex, and contribute to the relaxation of the upper esophageal sphincter (Steele, Bailey, Chau, Molfenter, Oshalla, Waito, & Zoratto, 2011, Pearson, Langmore, & Zumwalt, 2011; Pearson, Langmore, & Zumwalt, 2012; McFarland, 2015; Vandaele, Perlman, & Cassell, 1995).

Intrinsic Muscles of the Larynx

These muscles are responsible for approximation of the arytenoid cartilages (downward, forward, and inward rotation), adduction (closure) of the vocal folds, as well approximation of the ventricular (false) vocal folds. As stated in Chapter 1, the vagus nerve can be divided into the following branches that arise in the neck: Pharyngeal branches, Superior Laryngeal Nerve Branch (SLN), and Recurrent Laryngeal Nerve Branch (RLN). All intrinsic muscles of the larynx are innervated by the Recurrent Laryngeal Nerve Branch of Cranial Nerve X (Vagus), with the exception of the cricothyroid, which is innervated by the external branch of the Superior Laryngeal Nerve of Cranial Nerve X (Vagus) (McFarland, 2015; Vandaele, Perlman, & Cassell, 1995).

Muscles of the Pharynx

The muscles of the pharynx’s job are to contract upon the bolus. These sequential contractions create positive pressure behind the bolus, assisting in pushing it downwards toward the esophagus (McFarland, 2015; Vandaele, Perlman, & Cassell, 1995).

Clinician’s Note

The longitudinal pharyngeal muscles are often forgotten, but the palatopharyngeus, salinpingopharyngeus (also helps to equalize pressure in middle ear), and stylopharyngeus help to widen and shorten the pharynx with some elevation of the larynx, which in turn displaces the epiglottis to a horizontal position (McFarland, 2015; Vandaele, Perlman, & Cassell, 1995).