The pterygoid muscles are a crucial pair of muscles located deep within the skull, playing a primary role in the complex movements of the jaw. They are two of the four muscles essential for mastication (chewing), situated in a specialized area called the infratemporal fossa. These muscles are instrumental in enabling the diverse range of motions of the mandible (lower jaw) at the temporomandibular joint (TMJ).
The two distinct pterygoid muscles are:
- Lateral Pterygoid Muscle
- Medial Pterygoid Muscle
Together, their coordinated actions facilitate chewing, speaking, and other jaw functions.
Understanding the Pterygoid Muscles
The pterygoid muscles are named after their attachment to the pterygoid process of the sphenoid bone, a prominent structure at the base of the skull. Their unique orientation and attachments allow for precise control over the mandible's position and movement.
1. Lateral Pterygoid Muscle
The lateral pterygoid muscle is primarily responsible for the forward movement (protrusion) and side-to-side motion of the jaw. It's also the only muscle of mastication that actively helps in depressing (opening) the jaw.
- Origin: It has two heads:
- Superior Head: Arises from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone.
- Inferior Head: Arises from the lateral surface of the lateral pterygoid plate.
- Insertion: Primarily inserts into the neck of the condyle of the mandible and the articular disc and capsule of the temporomandibular joint.
- Actions:
- Protrusion: Pulls the mandible forward.
- Depression: Aids in opening the mouth (especially the inferior head).
- Lateral Excursion: Moves the jaw from side to side when acting unilaterally (one side at a time).
For a deeper dive into its anatomy, you can explore resources like Kenhub's article on the lateral pterygoid muscle.
2. Medial Pterygoid Muscle
The medial pterygoid muscle works in synergy with the masseter muscle to elevate and protrude the jaw, providing significant power during chewing.
- Origin: It also has two heads:
- Deep Head: Arises from the medial surface of the lateral pterygoid plate.
- Superficial Head: Arises from the tuberosity of the maxilla and the palatine bone.
- Insertion: Inserts into the medial surface of the ramus and angle of the mandible.
- Actions:
- Elevation: Closes the mouth.
- Protrusion: Aids in pushing the jaw forward.
- Lateral Excursion: Contributes to side-to-side grinding motions, especially when acting unilaterally.
You can find more detailed information on the medial pterygoid muscle via TeachMeAnatomy's muscles of mastication section.
Functions and Movements of the Mandible
The primary function of the pterygoid muscles is to produce movements of the mandible at the temporomandibular joint. These movements are critical for various daily activities.
| Muscle | Primary Actions |
|---|---|
| Lateral Pterygoid | - Protrusion (forward movement) - Depression (opening the mouth) - Lateral Excursion (side-to-side movement) |
| Medial Pterygoid | - Elevation (closing the mouth) - Protrusion (forward movement) - Lateral Excursion (side-to-side movement) |
Key Mandibular Movements facilitated by Pterygoid Muscles:
- Protrusion: Moving the lower jaw straight forward (e.g., biting into an apple). Both pterygoids contribute.
- Retrusion: Moving the lower jaw straight backward (achieved by other muscles like the temporalis, but the pterygoids play a role in coordinating the return).
- Elevation: Closing the mouth (primarily medial pterygoid, alongside masseter and temporalis).
- Depression: Opening the mouth (primarily lateral pterygoid, alongside suprahyoid muscles).
- Lateral Excursion (Grinding/Chewing): Moving the jaw from side to side (e.g., grinding food). This involves alternating contraction of the pterygoid muscles on opposite sides. For instance, the left lateral pterygoid and right medial pterygoid contract together to move the jaw to the right.
Clinical Relevance and Practical Insights
Understanding the pterygoid muscles is crucial in several medical and dental fields:
- Temporomandibular Joint (TMJ) Disorders: Dysfunction or spasm in the pterygoid muscles can lead to pain, clicking, and limited jaw movement, common symptoms of TMJ disorders.
- Dental Procedures: Dentists and oral surgeons need a thorough understanding of these muscles during procedures involving the jaw and surrounding structures.
- Bruxism (Teeth Grinding): Overactivity of the pterygoids, especially the medial pterygoid, can contribute to bruxism, leading to wear on teeth and muscle soreness.
- Trigger Points: These muscles are common sites for myofascial trigger points, which can cause referred pain in the face, head, and ear.
Proper function of the pterygoid muscles is essential for efficient chewing, clear speech, and overall oral health.
