1/17: Muscles of Mastication Flashcards
How many maxillary bones are there?
2
Where are the maxillary bones fused together?
At the mid-palatal suture
What is the superior border of the maxilla?
Floor of the nasal cavity and orbit
What is the inferior border of the maxilla?
Palate and alveolar ridge
What are the two components of the maxilla?
Body and processes
What make up the processes?
Zygomatic
Frontal
Alveolar
Palatine
What is the largest and strongest bone on the skull?
Mandible
What two components make up the mandible?
Body and ramus
What is the superior aspect of the mandible?
Alveolar crest and teeth
What parts make up the body-posterior aspect of the mandible?
Mandibular angle
Ascending Ramus
What makes up the ascending ramus?
Coronoid process and condyle
What does the condyle articulate with?
The cranium
What poles make up the condyle?
Medial and lateral poles
What is the mediolateral length of the condyle?
15-20 mm
What is the anterior-posterior width?
8-10 mm
What does the squamous portion of the temproal bone articulate with?
The mandibular condyle
What are the two fossa’s of the temporal bone?
Articular or glenoid fossa
What is the articular eminence?
Thick dense bone to tolerate heavy forces
What are the muscles of mastication?
Lateral pterygoids
Medial pterygoid
Temporalis
Masseter
What are the two heads of the masseter?
Superficial
Deep
How do the superficial head fibers of the masseter run?
Downward and backward
How do the deep deep head fibers of the masseter run?
Fibers run in a vertical direction
What is the origin of the masseter?
Anterior 2/3 of lower border of Zygomatich arch
What is the insertion of the masseter?
Lateral surface of ramus coronoid process and angle of the mandible
What is the funciton of the masseter?
Elevates the mandible
Powerful muscle providing the force for chewing
What does the superficial head of the masseter aid in?
Protrusion
What is the function of the deep head of the masseter?
Stabilizes the condyle against the emence
What is the blood supply of the masseter?
A muscular branch of the maxillary artery
What is the nerve supply of the masseter?
Masseteric nerve of mandibular division of trigeminal nerve
What are the three distinct divisions of the temproalis?
Anterior
Middle
Posterior
How do the fibers run in the anterior division of the temporalis?
Vertical directed fibers
How do the fibers run in the middle divison of the temporalis?
Fibers run obliquely across lateral aspect of the skull
How do the fibers run in the posterior division of the temporalis?
Horizontal fibers come forward above the ear to join other temporalis fibers
What is the origin of the temporalis?
Temporal fossa and lateral surface of the skull
What is the insertion of the temporalis?
Coronoid process and anterior border of ascending ramus
What is the action of the anterior temporalis?
Mandible is raised vertically
What is the action of the middle temporalis?
Elevates and retrudes the mandible
What is the action of the posterior temporalis?
Aids in retrusion of the mandible
What is the blood supply of the temporalis?
A muscular branch of the maxillary artery
What is the nerve supply of the temporalis?
Deep temporal nerve of the mandibular division of the trigeminal nerve
What are the two heads of the lateral (external) pterygoid?
- Superior lateral pterygoid
- Inferior lateral pterygoid
What is the origin of the inferior lateral pterygoid?
Outer surface of lateral pterygoid plate
What is the insertion of the inferior lateral pterygoid?
Neck of condyle
Where does the inferior lateral pterygoid extend?
Backward, upward, and outward
What does the bilteral contraction of the inferior lateral pterygoid cause?
The condyles to be pulled down the articular eminences and the mandible is protruded
What does the unilateral contraction of the inferior lateral pterygoid cause?
Mediotrusive movement (downward, forward, and medially)
What is the smallest of the two bellies?
Superior lateral pterygoid
What is the origin of the superior lateral pterygoid?
Infratemporal surface of the greater sphenoid wing
What is the insertion of the superior lateral pterygoid?
Disk, capsule, and neck of the condyle
When is the superior lateral pterygoid inactive?
During mandibular opening
When is the superior lateral pterygoid active?
Only with elevator muscle (closure of the mandible)
What muscle is active during mandibular closure against resistance (chewing or clenching)?
Superior lateral pterygoid (power stroke)
What is the blood supply of the lateral pterygoid?
A muscular branch of the maxillary artery
What is the nerve supply of the lateral pterygoid?
A branch of the masseteric or buccal nerve of the mandibular division of the trigeminal nerve
What is the origin of the medial (internal) pterygoid?
Pterygoid fossa
What is the insertion of the medial (internal) pterygoid?
Medial surface of the mandibular angle
What are the 3 functions of the medial (internal) pterygoid?
- Elevates the mandible
- Protrudes the mandible
- Unilateral contraction
What does unilateral contraction result in?
Mediotrusion
What is the blood supply of the medial (internal) pterygoid?
A muscular branch of the maxillary artery
What is the nerve supply of the medial (internal) pterygoid?
A motor branch of the mandibular division of the trigeminal nerve, which reaches the posterior border of the muscle near the base of the skull
What makes up the masseter sling?
Masseter
Medial pterygoid
What is the group that makes up the suprahyoids?
Geniohyoid
Mylohyoid
Digastric
Stylohyoid
What is the function of the suprahyoids?
Elevate hyoid bone
Depress the mandible when hyoid bone is fixed
What is the origin of the geniohyoid?
Inferior genial tubercle on the inner surface of mandibular symphysis
What is the insertion of the geniohyoid?
Anterior surface of body of hyoid bone
What is the origin of the mylohyoid?
Line from last molar root to mandibular symphysis
What is the insertion of the mylohyoid?
Median raphe from chin to hyoid bone
What two belles make up the digastric?
Anterior
Posterior
What is the origin of the posterior belly of the digastric muscle?
Mastoid process
Which belly is the longest in the digastric muscle?
Posterior
What is the origin of the anterior belly of the digastric muscle?
A depression on the inner side of the lower border of the mandible, close to the symphysis
What is the insertion of the digastric muscle?
Hyoid bone
What are mandibular movements?
Depression
Elevation
Right lateral
Left lateral
Protrusion
Retrusion
What muscles contract when depressing the mandible?
Inferior lateral pterygoids
Digastric
What muscles relax when depressing the mandible?
Masseters
Medial pterygoids
Temporalis
What muscles contract when elevating the mandible?
Masseters
Medial pterygoid
Temporalis
Superior lateral pterygoid
What muscles relax when elevating the mandible?
Inferior lateral pterygoid
Digastric
What muscles contract when the mandible has right lateral movement?
Left inferior lateral pterygoid
What muscles relax when the mandible has right lateral movement?
Right inferior lateral pterygoid
Slight relaxation of elevators
What muscles contract when the mandible has left lateral movement?
Right inferior lateral pterygoid
What muscles relax when the mandible has left lateral movement?
left inferior lateral pterygoid
Slight relaxation of elevators
What muscles contract when the mandible is protruding?
Inferior lateral pterygoids mainly
Assisted by masseters and medial pterygoids
What muscles contract when the mandibule retrudes?
Temporalis