The stylopharyngeus is a slender, elongated muscle of the pharynx that plays a key role in elevating and widening the pharynx during swallowing and speech.[3] It is part of the inner longitudinal muscle layer of the pharynx and works alongside other pharyngeal muscles.
Location
The stylopharyngeus muscle originates from the styloid process of the temporal bone in the skull. It descends between the superior and middle pharyngeal constrictor muscles and inserts into the posterior border of the thyroid cartilage and the pharyngeal wall. It is located in the lateral aspect of the pharynx, near the throat.[1]
Anatomy
The stylopharyngeus muscle is a slender, elongated muscle that is part of the longitudinal muscle group of the pharynx. Below is a detailed description of its anatomy:
Origin
The stylopharyngeus muscle arises from the medial aspect of the styloid process of the temporal bone, near its base.
Course
- The muscle descends obliquely in the neck, passing inferiorly and medially.
- It travels between the superior and middle pharyngeal constrictor muscles to reach the lateral wall of the pharynx.[8]
Insertion
The stylopharyngeus muscle inserts into:
- The posterior border of the thyroid cartilage (part of the larynx).
- The lateral wall of the pharynx, blending with the fibers of the palatopharyngeus and constrictor muscles.
Relationships
- Superiorly: Lies close to the base of the styloid process and the beginning of the stylohyoid ligament.
- Inferiorly: Inserts between the thyroid cartilage and the pharyngeal wall.
- Medially: Related to the pharynx and its constrictor muscles.[5]
- Laterally: Associated with the glossopharyngeal nerve (cranial nerve IX), which runs along the muscle.
Nervous Supply
- The stylopharyngeus muscle is unique among pharyngeal muscles as it is the only muscle innervated by the glossopharyngeal nerve (cranial nerve IX).
- This nerve provides motor innervation to the muscle.
Blood Supply
Arterial Supply:
Supplied by branches of the:
- Ascending pharyngeal artery (a branch of the external carotid artery).
- Facial artery (ascending palatine branch).
Venous Drainage:
Drains into the pharyngeal venous plexus, which eventually empties into the internal jugular vein.[6]
Lymphatic Drainage
Lymphatic drainage of the stylopharyngeus follows the general pattern of the pharynx and drains into the deep cervical lymph nodes.
Relationships with the Glossopharyngeal Nerve
- The glossopharyngeal nerve runs along the lateral aspect of the stylopharyngeus muscle, providing its motor innervation.[7]
- The nerve continues toward the base of the tongue after passing this muscle.
Layer and Association
- The stylopharyngeus is part of the longitudinal muscle group of the pharynx, along with the palatopharyngeus and salpingopharyngeus muscles.
- It works in conjunction with these muscles to elevate and widen the pharynx during swallowing and speech.
Function
The stylopharyngeus muscle plays an essential role in swallowing and speech by modifying the shape and position of the pharynx and larynx. Below is a detailed explanation of its functions:
Elevation of the Pharynx and Larynx
The primary function of the stylopharyngeus muscle is to elevate the pharynx and larynx during swallowing and speech:
- Elevation shortens and widens the pharynx, creating space for the bolus of food to pass smoothly from the oropharynx to the esophagus.
- Laryngeal elevation helps protect the airway by allowing the epiglottis to cover the glottis during swallowing, preventing aspiration of food or liquids into the respiratory tract.
Widening of the Pharynx
The stylopharyngeus muscle pulls the lateral walls of the pharynx outward:
- This action increases the width of the pharyngeal lumen, facilitating the passage of larger food boluses.[4]
- The widening effect is particularly important during swallowing to minimize resistance in the pharynx.
Role in Swallowing (Deglutition)
The stylopharyngeus muscle coordinates with other longitudinal pharyngeal muscles (palatopharyngeus and salpingopharyngeus) to assist in the sequential phases of swallowing:
- It helps align and stabilize the pharynx for the peristaltic movement of food toward the esophagus.
- Works with the pharyngeal constrictors to guide food downward efficiently.
Contribution to Speech
During speech, the muscle’s ability to modify the shape and position of the pharynx contributes to:
- Resonance and clarity of voice.
- Proper positioning of the larynx for sound modulation.
Coordination with Glossopharyngeal Nerve
The muscle is innervated by the glossopharyngeal nerve (cranial nerve IX), which integrates motor signals to the muscle with sensory feedback from the pharynx and tongue:
This coordination ensures that pharyngeal elevation and widening occur reflexively during swallowing.
Assistance in Pressure Regulation
By widening the pharynx, the stylopharyngeus muscle may indirectly help regulate pressure during swallowing, balancing the forces between the oral cavity and the esophagus.
Clinical Significance
The stylopharyngeus muscle is crucial for swallowing, airway protection, and speech modulation, and its dysfunction can lead to significant clinical issues:
- Dysphagia (Difficulty Swallowing): Impaired function of the stylopharyngeus muscle, often due to damage to the glossopharyngeal nerve (cranial nerve IX), can result in difficulty elevating and widening the pharynx during swallowing, leading to food bolus retention or aspiration.
- Neurological Disorders: Conditions like strokes or cranial nerve palsies can impair the muscle’s function, causing dysphagia or impaired speech resonance.
- Glossopharyngeal Neuralgia: Pain along the glossopharyngeal nerve may indirectly affect the stylopharyngeus muscle, exacerbating swallowing difficulties.[2]
- Surgical Relevance: The stylopharyngeus is an important anatomical landmark during neck surgeries, particularly in procedures involving the pharynx, glossopharyngeal nerve, or carotid sheath.
