Please enable JavaScript.
Coggle requires JavaScript to display documents.
Myology OCF & TMJ - Coggle Diagram
Myology OCF & TMJ
MUSCLES INVOLVED IN A BROAD SMILE/LAUGHTER
Facial Expression Muscles (Main Conductors
Zygomaticus major: Pulls corners of mouth upward and outward (creating the broad smile).
Zygomaticus minor: Elevates the upper lip.
Risorius: Draws corners of the mouth laterally (widening the smile).
Levator labii superioris: Raises the upper lip to show upper teeth.
Buccinator: Keeps the cheek firm and prevents folding/bulging.
Masticatory Muscles (Assist/Stabilize)
Masseter: Stabilizes the lower jaw when the mouth opens widely during laughter.
Lateral Pterygoid: Helps open the mouth when laughing broadly.
Temporalis (posterior fibers): Aids in returning the jaw to normal position after a wide laugh.
Neck Muscles (Assist/Support)
Platysma: Tenses neck skin and pulls mouth corners downward (supports lower facial expression).
Sternocleidomastoid (SCM): Stabilizes the head and neck during vigorous laughter.
MANDIBULAR GROWTH AND SHAPE CHANGES
Embryologic Background
Mandible forms from the mandibular prominence of the first pharyngeal arch.
Initially develops by membranous ossification, with endochondral ossification only in the condyle.
Condyle Changes (Major Growth Site)
Undergoes endochondral ossification and reshaping during growth.
Allows elongation of the ramus and adjustment to the TMJ.
Childhood: Rounded, bulbous shape; grows through vertical and superior growth.
Adult: Flat, tapered shape; continues to adapt to the TMJ's functional stresses.
Mandibular Ramus Changes
Mechanism: Coordinated bone apposition (on the posterior surface) and resorption (on the anterior surface).
Result: This remodeling moves the ramus posteriorly (backward) for proper occlusion.
Ramus Height: Increases as growth continues.
Mandibular Angle: Changes from Oblique (140-130°) in childhood to More Acute (110-120°) in adulthood.
FACIAL EXPRESSION MUSCLES (Oral Region)
Named Based on Function
Levator Anguli Oris
Basis: "Levator" (elevate) and "Anguli Oris" (angle of the mouth).
Position: Originates from the canine fossa of maxilla; Inserts at the modiolus (angle of the lips).
Function: Elevates/draws the corner of the mouth superiorly.
Depressor Anguli Oris
Basis: "Depressor" (depresses) and "Anguli Oris" (angle of the mouth).
Position: Originates from the mandible (external oblique line area); Inserts at the corner of the mouth.
Function: Lowers the mouth corner (sadness/anger expression).
Named Based on Fiber Shape
Buccinator
Basis: Named after "bucca" (cheek); fibers spread like a flat sheet.
Function: Compresses cheek against teeth ; prevents cheek folding; aids in sucking/blowing.
Orbicularis Oris
Basis: "Orbicularis" (circular) and "Oris" (mouth); fibers are arranged in concentric rings.
Function: Closes and protrudes the lips (sphincter of the oral region).
MUSCLES OF MASTICATION
Main Muscles and Functions
Masseter: Elevates and causes protrusion of the mandible.
Temporalis: Elevates and retracts the mandible (posterior fibers).
Medial Pterygoid: Elevates and assists protrusion.
Lateral Pterygoid: Protrudes and controls opening/condyle translation at the TMJ.
Innervation: All are innervated by the Mandibular division of the Trigeminal nerve (CN V3).
FUNCTIONAL DIFFERENCE (Attachment)
Facial Expression Muscles
Attachment: Insert into skin and superficial fascia.
Force: Designed for subtle forces for emotional display.
Function: Primarily nonverbal communication, closing the lips, and shaping the mouth.
Masticatory Muscles
Attachment: Insert directly into bone (Mandible) and the craniofacial skeleton (e.g., temporal bone).
Force: Designed to exert high forces for chewing/biting.
Function: Primarily food breakdown, mandibular posture, and generating power.