Salpingopharyngeus muscle

The salpingopharyngeus muscle is a small, longitudinal muscle in the pharynx that contributes to the elevation of the pharynx and larynx during swallowing and speech.^[3] It also helps open the auditory tube to equalize pressure between the middle ear and the pharynx. This muscle is often considered part of the inner longitudinal layer of the pharyngeal muscles.

Location

The salpingopharyngeus muscle originates from the cartilaginous part of the auditory (Eustachian) tube in the nasopharynx. It descends along the lateral wall of the pharynx and blends with the palatopharyngeus muscle, inserting into the side of the pharynx.^[4]

Anatomy

The salpingopharyngeus muscle is a slender muscle of the pharynx that plays a role in swallowing and pressure regulation within the auditory tube. Below is a detailed description of its anatomy:

Origin

• The salpingopharyngeus muscle arises from the inferior border of the cartilaginous part of the auditory (Eustachian) tube, located in the nasopharynx.^[5]
• It originates near the pharyngeal orifice of the auditory tube.

Insertion

• The muscle descends along the lateral wall of the pharynx.
• It blends with the fibers of the palatopharyngeus muscle and attaches to the posterior border of the thyroid cartilage and the pharyngeal wall.^[2]

Structure

• The salpingopharyngeus is a narrow, strap-like muscle and is one of the inner longitudinal muscles of the pharynx.
• It is often difficult to distinguish from the palatopharyngeus muscle due to their close association and blending of fibers.

Layer and Relationships

• The salpingopharyngeus muscle is part of the longitudinal layer of the pharyngeal muscles, which also includes the stylopharyngeus and palatopharyngeus muscles.
• It lies deep to the mucosa of the nasopharynx and pharynx and is lateral to the superior constrictor muscle.

Nervous Supply

• Innervated by the vagus nerve (cranial nerve X) through the pharyngeal plexus.
• It receives motor innervation indirectly, as part of the coordinated action of pharyngeal muscles during swallowing.^[6]

Blood Supply

The salpingopharyngeus muscle is supplied by branches of the:

• Ascending pharyngeal artery, a branch of the external carotid artery.
• Ascending palatine artery, a branch of the facial artery.

Lymphatic Drainage

Lymphatic drainage follows the pattern of the pharynx and drains into the deep cervical lymph nodes.

Relationships to Adjacent Structures

• Superiorly: Related to the cartilaginous part of the auditory tube.
• Inferiorly: Merges with the fibers of the palatopharyngeus muscle.
• Anteriorly: Lies close to the nasopharyngeal mucosa.
• Posteriorly: Related to the superior pharyngeal constrictor muscle.

Histological Features

• The muscle is composed of skeletal muscle fibers, enabling voluntary control during swallowing and speech.
• It is covered by a layer of connective tissue and pharyngeal mucosa.

Function

The salpingopharyngeus muscle is a small yet essential muscle in the pharynx that contributes to various physiological processes involving the throat and auditory tube. Below is a detailed explanation of its functions:

Elevation of the Pharynx and Larynx

The salpingopharyngeus muscle assists in elevating the pharynx and larynx during swallowing and speech:

• Elevation of the pharynx shortens its length, making it easier to propel food and liquids from the oropharynx into the esophagus.^[7]
• Elevation of the larynx protects the airway by ensuring the epiglottis covers the glottis during swallowing.

Assistance in Swallowing (Deglutition)

The muscle works synergistically with other longitudinal pharyngeal muscles (stylopharyngeus and palatopharyngeus) and pharyngeal constrictors to facilitate swallowing: It pulls the lateral walls of the pharynx inward, narrowing the lumen and aiding in the smooth passage of food and liquids.

Opening of the Auditory (Eustachian) Tube

The salpingopharyngeus muscle plays a critical role in equalizing air pressure between the middle ear and the nasopharynx by:

• Opening the auditory tube during swallowing, yawning, or other activities that involve pharyngeal muscle contraction.
• This function helps maintain balance and hearing by preventing pressure differences that could damage the tympanic membrane (eardrum).

Contribution to Pressure Regulation

By connecting the auditory tube to the pharynx, the salpingopharyngeus aids in regulating pressure changes in the ear during altitude shifts (e.g., flying or diving).^[8]

Coordination in Speech

Elevation and tension adjustments in the pharynx by the salpingopharyngeus muscle contribute to voice modulation and resonance during speech.

Role in Immune Defense

While indirectly related, the muscle’s function in opening the auditory tube helps maintain the drainage and ventilation of the middle ear, reducing the risk of infections such as otitis media.

Clinical Significance

The salpingopharyngeus muscle is clinically significant due to its role in swallowing, auditory tube function, and pressure regulation:

• Eustachian Tube Dysfunction: Impaired function of the salpingopharyngeus can lead to difficulty in opening the auditory tube, causing issues like ear barotrauma, middle ear effusion, or recurrent otitis media.
• Swallowing Disorders (Dysphagia): Dysfunction of the salpingopharyngeus muscle may contribute to swallowing difficulties, particularly in conditions affecting the coordination of pharyngeal muscles.
• Speech and Resonance Disorders: Improper functioning of the muscle can impact voice modulation and resonance, affecting speech clarity.^[1]
• Neurological Conditions: Damage to the vagus nerve or the pharyngeal plexus (e.g., due to stroke or trauma) may impair salpingopharyngeus activity, leading to compromised swallowing and auditory tube dysfunction.