The pterygoid plates are bony structures located deep within the skull, extending from the sphenoid bone, which forms a significant part of the skull base. They serve as rigid anchors for powerful muscles, playing a fundamental role in the mechanics of the jaw and upper throat. These plates enable essential functions like chewing and swallowing.
Anatomy and Position within the Skull
The pterygoid plates project downward from the sphenoid bone’s body and its greater wings, situated behind the upper jaw bone (maxilla). They form a boundary, marking the posterior limit of the nasal cavity and the roof of the pharynx (throat). Each pterygoid process consists of two thin, vertical sheets of bone: the medial and lateral plates.
The plates diverge as they extend backward, creating a V-shaped depression known as the pterygoid fossa. This fossa provides a sheltered space for muscle attachments. The Lateral Pterygoid Plate is broader and thinner, facing outward toward the cheek area.
The Medial Pterygoid Plate is narrower and longer, oriented toward the midline of the body. This plate terminates at its lower end with a small, hook-like projection called the Hamulus. The hamulus acts much like a pulley, redirecting the path of a muscle tendon.
The lateral surface of the lateral plate forms the medial wall of the infratemporal fossa, a space below the temporal bone. This protected positioning highlights their role as internal buttresses and foundational points for the musculature that controls the lower jaw. The plates are fused superiorly but separate inferiorly to connect with other facial bones.
Essential Role in Jaw Movement and Swallowing
The pterygoid plates are indispensable for the mechanics of the mouth and throat, functioning primarily as robust attachment sites for several muscles. These muscles control the movements of the lower jaw, which is vital for consuming food. The plates translate muscle contraction into the complex motions required for chewing.
Two major muscles of mastication, the Medial and Lateral Pterygoid muscles, anchor directly onto these plates. The Lateral Pterygoid muscle originates from the lateral pterygoid plate and the greater wing of the sphenoid. Its contraction is responsible for opening the jaw and performing side-to-side movements necessary for grinding food.
The deep head of the Medial Pterygoid muscle takes its origin from the medial surface of the lateral pterygoid plate, while its superficial head attaches elsewhere. This muscle works in conjunction with the masseter muscle to elevate the mandible, forcefully closing the jaw to crush food. If the muscles on only one side contract, they create the lateral, grinding motion of the jaw.
Beyond chewing, the plates are involved in the process of swallowing and breathing through the attachment of the Tensor Veli Palatini muscle. This muscle originates near the base of the medial plate and wraps its tendon around the hamulus. This unique pulley system allows the muscle to tense the soft palate, which is necessary to seal off the nasal cavity during swallowing.
The Tensor Veli Palatini’s contraction also assists in opening the auditory (Eustachian) tube, which connects the middle ear to the back of the throat. This action helps to equalize air pressure across the eardrum, a sensation often felt when swallowing or yawning. The anchoring provided by the pterygoid plates is linked to ear health and throat function.
Medical Relevance and Potential Issues
The location of the pterygoid plates at the base of the skull makes them a significant indicator in cases of facial trauma. A fracture of one or both plates is commonly associated with severe mid-face injuries. In the Le Fort classification system, involvement of the pterygoid plates is a characteristic feature used to confirm the severity of the injury.
The plates’ involvement in these fractures signals a high-impact force that has separated the facial skeleton from the skull base. While frequently seen alongside other fractures, an isolated pterygoid plate fracture, though rare, can occur from localized trauma. These fractures require careful assessment as they can indicate complex injuries to surrounding structures.
The pterygoid region is also an anatomical landmark for surgeons operating on the skull base or deep facial structures. In orthognathic surgery, which involves repositioning the jaw, the plates sometimes interfere with the desired movement of the maxilla. Surgeons may intentionally fracture or remove a portion of the pterygoid plate to create sufficient space for the maxilla to be moved backward.
Issues with the muscles attached to the plates can also cause pain that is sometimes mistakenly attributed to dental or sinus problems. Dysfunction in the Medial or Lateral Pterygoid muscles is a component of Temporomandibular Joint Disorder (TMD). In TMD, muscle tension or spasm can lead to referred pain in the face, head, or neck. Understanding the connection between the muscles and their bony anchors helps in diagnosing the source of this deep facial pain.