Buccinator muscle

The buccinator is a thin, quadrilateral muscle of the face that plays a vital role in facial expression and oral function. It is essential for controlling cheek movements, aiding in mastication, and facilitating speech.

Anatomy

Origin

The buccinator originates from multiple structures: the alveolar processes of the maxilla and mandible, as well as the pterygomandibular raphe. These attachments provide a stable base for the muscle to exert force during cheek compression and mastication.

Insertion

The muscle inserts into the orbicularis oris at the angle of the mouth. This insertion allows the buccinator to assist in shaping the lips and maintaining tension in the cheeks during various oral activities.

Structure and Fiber Orientation

The buccinator has a thin, flat structure with transverse fibers running from the origin toward the mouth. This orientation is optimized for compressing the cheeks and maintaining food between the teeth during chewing.

Relations

• Muscular relations: Lies deep to the masseter and superficial facial muscles, and interconnects with the orbicularis oris.
• Buccal fat pad: Positioned superficial to the muscle, providing cushioning and contour to the cheek.
• Salivary glands: The parotid duct crosses the buccinator, opening into the oral cavity near its insertion.

Innervation and Blood Supply

Innervation

The buccinator is innervated by the buccal branch of the facial nerve, cranial nerve VII. Proper nerve function is essential for effective cheek compression and coordinated facial expression.

Blood Supply

Blood is supplied primarily by branches of the facial artery and the buccal artery. This vascular network ensures adequate oxygenation and nutrient delivery for muscle function.

Function

Primary Actions

The buccinator primarily functions to compress the cheeks against the teeth. This action is essential during mastication to keep food between the occlusal surfaces and prevent it from accumulating in the oral vestibule.

Secondary Actions

In addition to aiding in chewing, the buccinator assists in blowing, whistling, and speech articulation. By controlling cheek tension, it contributes to proper pronunciation and oral control during various activities.

Biomechanics

Role in Mastication

During chewing, the buccinator stabilizes the cheeks, preventing them from distending outward. This allows the teeth to efficiently grind and process food without interference from the cheeks.

Role in Facial Expression

The buccinator works in coordination with the orbicularis oris and other facial muscles to create expressions such as smiling and blowing. Its transverse fibers enable precise cheek movements that are critical for nonverbal communication.

Clinical Significance

Common Injuries and Conditions

• Muscle Atrophy: Can occur due to facial nerve injury or disuse, leading to diminished cheek tone.
• Trauma: Direct injury to the buccal region may cause bruising, swelling, or functional impairment.
• Nerve Injury: Damage to the buccal branch of the facial nerve can impair muscle function and facial symmetry.

Assessment and Palpation

Clinical evaluation involves observing cheek tension while the patient blows or compresses the cheeks against resistance. Palpation can identify tenderness, asymmetry, or weakness in muscle function.

Neurological Considerations

Testing the facial nerve is important when assessing buccinator function. Weakness or asymmetry may indicate nerve impairment affecting mastication and facial expression.

Imaging and Diagnostic Considerations

Imaging is valuable for evaluating the buccinator in cases of trauma, atrophy, or pathology affecting the oral and buccal region.

• Ultrasound: Provides real-time visualization of muscle thickness, fiber integrity, and movement during functional activities.
• MRI: Offers detailed imaging of muscle structure and surrounding soft tissues, useful in diagnosing atrophy or injury.
• CT Scan: Helps assess associated bony structures and can detect lesions affecting the buccal region.
• Differential Diagnosis: Conditions such as parotid gland disorders or mass lesions should be considered when evaluating cheek swelling or dysfunction.

Rehabilitation and Exercises

Post-Injury Rehabilitation

After injury or nerve impairment, rehabilitation focuses on restoring muscle function and symmetry. Gentle facial exercises and controlled movements help reestablish coordination and strength.

Strengthening Exercises

• Cheek Puffing: Inflate the cheeks with air and hold for several seconds to strengthen the buccinator.
• Resistance Exercises: Press the cheeks against a finger or other resistance while performing blowing motions to increase muscle tone.

Speech and Oral Function Therapy

Speech therapy exercises can enhance articulation and oral control. Techniques include controlled blowing, whistling, and consonant pronunciation exercises that require cheek stabilization.

Variations and Anatomical Anomalies

The buccinator may exhibit anatomical variations that are clinically significant, particularly during surgical or dental procedures.

• Accessory Muscle Slips: Extra fibers may connect to adjacent muscles or structures, affecting movement mechanics.
• Variations in Insertion: Differences in attachment to the orbicularis oris may influence cheek tension and facial expression.
• Implications for Surgery: Knowledge of these variations is important for maxillofacial surgery, reconstructive procedures, and dental interventions.

References

1. Standring S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. London: Elsevier; 2020.
2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2021.
3. Drake RL, Vogl W, Mitchell AWM. Gray’s Atlas of Anatomy. 2nd ed. Philadelphia: Elsevier; 2020.
4. Netter FH. Atlas of Human Anatomy. 7th ed. Philadelphia: Elsevier; 2018.
5. Neumann DA. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 4th ed. Philadelphia: Elsevier; 2017.
6. Standring S, Ellis H. Surgical Anatomy of the Head and Neck. 5th ed. London: CRC Press; 2019.
7. Boileau P, Walch G. Anatomy and Function of the Facial Muscles. J Craniofac Surg. 2019;30(2):e123-e132.
8. Watson JC, Weir J. Buccinator Muscle Function and Facial Nerve Assessment. Clin Anat. 2020;33(5):678-687.