Mastication, TMJ and Swallowing Flashcards
What allows us for the movement of the mandible?
This movement is due to the synovial joint between the mandible and the temporal bone.
Where is the articular disc found?
It is found above the head of the mandible and below the temporal bone.
What 6 movements does the articular disc allow for?
Lateral deviation (moving left to right), protrusion&retraction (moving mandible forwards and backwards), elevation and depression.
What two movements can the mandible do in respect to the temporal bone?
The mandible can either deviate or rotate in respect to the temporal bone.
The deviation is between the upper compartment of the moving disc and the stationary fossa (space).
The rotation is between the lower compartment between the stationing disc and the moving condyle of the mandible.
Where do we find the infra temporal fossa?
What does the fossa allow for?
Found behind the maxilla and deep to the zygomatic arachnoid and the ramus of the mandible.
The fossa is of relevance to the muscles of mastication as it allows the passage of the temporalis and pterygoid muscles. It also allows the passage of the maxillary artery and the pterygoid venous plexus.
Explain briefly the blood and venous supply to the masticatory muscles
The muscles of mastications receive blood supply from the maxillary artery, the larger of the two terminal branches of the external carotid.
The length of this artery is subdivided into mandibular, pteygoid and pterygopalatine.
The equivalent drainage is called the pterygoid venous plexus.
What nerve innervates the muscles of mastication?
The mandibular nerve (V3).
Where does the pterygoid plexus of veins lie?
Between the temporalis and pterygoid muscles and anastomoses with the facial vein and the cavernous sinus.
(The facial vein is the most important vein for drainage. This drains into the internal jugular and then into the subclavian artery)
Name the 4 main muscles of mastication?
Masseter
Temporalis
Medial pterygoid
Lateral pterygoid
Where is the masseter muscle found?
What are the actions of the masseter muscle?
Originates from the zygomatic bone and inserts into the ramus of the mandible.
Masseter muscle action:
Elevation = uses both masseter muscles, enabling the teeth to be clenched
Retrusion = uses the superficial fibres of both masseter muscles, retruding a protruded mandible
Ipsilateral excursion = a single masseter can move the mandible to the same side.
Where is the temporalis muscle found?
What is the muscle action?
It originates from the side of the skull and inserts to the coronoid process of the mandible.
Resting tonus - maintaining the mandible at rest position when the subject is upright
Elevation - e.g. when chewing
Retrusion - this involves the posterior horizontal fibres of both sides retruding a protruded mandible
Ipsilateral excursion - using only one side of the temporalis is capable of pulling the mandible to one side.
Where are the medial and lateral pterygoid muscles found?
They occupy the infratemporal fossa.
To the seen when a portion of the mandible is removed.
The medial pteryoid is a mirror of the masseter muscle, but on the inside of the mandible.
What is the muscle action of the medial pteryoid muscle?
Elevation - acting together, the medial pterygoid plus master are powerful elevators
Protrusion - together the right and left muscles aid in protruding the jaw
Contralateral excursion - the medial pterygoid from one side moves the jaw to the opposite side
What is the only muscle of mastication with horizontal fibres?
The lateral pterygoid muscle.
What is the muscle action of the lateral pterygoid muscle?
Profusion - both sides together are prime protractors. Also the horizontal fibres pull the mandible forwards onto the articular disc.
Depression - both sides together not only pull the mandible forwards but depress when combines with the hyoid muscles.
Contralateral excursion - one side moves the mandible in the opposite direction
