Anatomy and Origin
The medial pterygoid muscle belongs to the group of muscles of mastication, which also includes the masseter, temporalis, and lateral pterygoid muscles.
- Origin (origo) — pterygoid fossa (fossa pterygoidea).
- Insertion (insertio) — pterygoid tuberosity (tuberositas pterygoidea).
- Blood supply — branches of the maxillary artery (a. maxillaris).
- Innervation — V3.
- Fascial relations — the proximal segments of the mandibular nerve and the medial pterygoid muscle are enclosed by the interpterygoid fascia.
Topography and Adjacent Structures
The medial pterygoid muscle forms the boundaries of several key facial fascial spaces:
- Pterygomandibular space — the muscle forms its medial boundary, while the inner surface of the mandibular ramus forms the lateral boundary. The inferior alveolar nerve (n. alveolaris inferior) descends into this space.
- Parapharyngeal space (spatium parapharyngeum) — the medial pterygoid muscle forms its lateral wall.
- Interpterygoid fascial space — bounded medially by this muscle and laterally by the lateral pterygoid muscle. Branches of the mandibular nerve pass through this interval.
- Retromandibular region — the medial pterygoid muscle, along with the posterior border of the mandibular ramus, forms its anterior boundary.
- Intermandibular space — the medial pterygoid muscle serves as the inferior boundary of this region.
Clinical Significance
The anatomical position of the muscle is critical in oral and maxillofacial surgery and dentistry:
- Spread of infection: when an infection originates near the lingual side of the lower molars, the inflammatory process can spread beneath the medial pterygoid muscle. Clinically, this presents with tissue infiltration and marked trismus (grade II–III).
- Surgical approaches: the inner surface of the medial pterygoid muscle serves as a landmark during blunt tissue dissection to drain abscesses and phlegmons of the parapharyngeal space. In extraoral approaches to pterygomandibular space phlegmons, a portion of the medial pterygoid muscle tendon is surgically detached.
- Reconstructive surgery: during conservative mandibular resection, the masseter (m. masseter) and medial pterygoid (m. pterygoideus medialis) muscles are sutured to the angle of the mandible to stimulate and enhance bone tissue regeneration.
- Local anesthesia: the interpterygoid fascia covering the medial pterygoid muscle acts as the medial boundary of the pterygomandibular space, preventing the local anesthetic solution from diffusing outside the target zone.