Lecture 2- Muscles of Mastication Flashcards
how many maxillary bones are there and what fuses them together
-2 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 maxillar
palate and alveolar ridge
what are the components of the maxilla
-body
-zygomatic process
-frontal process
-alveolar process
-palatine process
what is the largest and strongest bone on the skull
the mandible
what is the superior aspect of the mandible
alveolar crest and teeth
what is the posterior aspect of the mandible
-mandibular angle
-ascending ramus
-coronoid process
-condyle
what does the condyle articulate with
the cranium
what is the medoilateral length of the condyle
15-20 mm
what is the anterior-posterior width of the condyle
8-10 mm
what does the squamous portion of the temporal bone articulate with
the mandibular condyle
what is the articular eminence of the temporal bone
thick dense bone to tolerate heavy forces
what are the muscles of mastication
-lateral pterygoids
- medial pterygoids
- temporalis
-masseter
what direction do fibers of the superficial masseter and deep masseter run
-superficial: fibers run downwards and backwards
-deep: vertical
what is the origin and insertion of the masseter
-origin: zygomatic arch
-insertion: lateral surface of ramus and angle of mandible
what are the actions of the masseter
-elevates the mandible
-provides force for chewing
-superficial head: aids in protrusion
- deep head: stabilizes the condyle against the eminence
what is the blood supply to the masseter
muscular branch of the maxillary artery
what innervates the massester
masseteric nerve of mandibular division of the trigeminal nerve
what are the 3 divisions of the temporalis and what direction do the fibers run
-anterior- vertical directed fibers
- middle- oblique across lateral aspect of the skull
- posterior: horizontal fibers come forward above the ear to join other temporalis fibers
what is the origin and insertion of the temporalis
-origin: temporal fossa and lateral surface of the skull
- insertion: coronoid process and anterior border of ascending ramus
what are the actions of each division of the temporalis
-anterior: mandible is raised vertically
- middle: elevates and retrudes the mandible
- posterior: aids in retrusion of the mandible
what is the blood supply and nerve supply of the temporalis
-blood: a muscular branch of the maxillary artery
- nerve: deep temporal nerve of the mandibular division of trigeminal nerve
what are the 2 heads of the lateral pterygoid
-superior lateral pterygoid
- inferior lateral pterygoid
what is the origin and insertion of the inferior lateral pterygoid and where does it extend
- origin: outer surface of lateral pterygoid plate
- insertion: neck of condyle
extends: backwards upwards and outwards
what are the actions of the inferior lateral pterygoid
-bilateral contraction: causes the condyle to be pulled down the articular eminence and the mandible is protruded
- unilateral contraction: causes mediotrusive movement - downward, forward and medially
what is the origin and insertion of the superior lateral pterygoid
- origin: infratemporal surface of the greater sphenoid wing
- insertion: disk , capsule, and neck of the condyle
what belly is smaller in the lateral pterygoid
superior lateral
what are the actions of the superior lateral pterygoid
-inactive during mandibular opening
- active only with elevator muscles (closing of the mandible)
- power stroke: this muscle is active during mandibular closure against resistance (chewing or clenching)
what is the blood and nerve supply to the lateral pterygoid
-blood: a muscular branch of the maxillary artery
- nerve: a branch of the masseteric or buccal nerve of the mandibular division of the trigeminal nerve
what is the origin and insertion of the medial pterygoid
-origin: pterygoid fossa
- insertion: medial surface of the mandibular angle
what are the functions of the medial pterygoid
- elevates the mandible
- protrudes the mandible
-unilateral contractions
results in mediotrusion
what is the blood and nerve supply to the medial pterygoid
-blood: a muscular branch of the maxillary artery
- nerve: 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 muscles make up the masseter sling
masseter and medial pterygoid
what muscles make up the suprahyoids
-geniohyoid
- mylyhyoid
-digastric
-stylohyoid
what are the functions of the suprahyoids
-elevate hyoid bone and depresses the mandible when hyoid bone is fixed
what is the origin and insertion of the geniohyoid
origin: inferior genial tubercle on the inner surface of the mandibular symphysis
insertion: anterior surface of body of hyoid bone
what is the origin and insertion of the mylohyoid
origin: line from last molar root to mandibular symphysis
insertion: median raphe from chin to hyoid bone
what are the 2 bellies of the digastric
anterior and posterior
what is the origin and insertion of the digastric
origin: the posterior belly, longer than the anterior, arises from the mastoid process. the anterior belly arises from a depression on the inner side of the lower border of the mandible, close to the symphysis
insertion: hyoid bone
what muscles contract during depression of the mandible
-inferior lateral pterygoid
-digastric
what muscles relax during depression of the mandible
-masseters
-medial pterygoids
- temporalis
what muscles contract during elevation of the mandible
-masseters
- medial pterygoid
- temporalis
-superior lateral pterygoid
what muscles relax during elevation of the mandible
-inferior lateral pterygoid
- digastric
what muscles are contracting and relaxing during right lateral movement
contraction: left inferior lateral pterygoid
relaxation: right inferior lateral pterygoid and slight relaxation of elevators
what contracts and relaxes during left lateral movement
contraction: right inferior lateral pterygoid
relaxation: left inferior lateral pterygoid, slight relaxation of elevators
what contracts during protrusion
mainly inferior lateral pterygoids assisted by masseters and medial pterygoids
what is contracting during retursion
temporalis
