Topic 1 (Muscles of Mastication) Flashcards
It is defined as the process of food chewing in preparation for swallowing and digestion.
Mastication
It is defined as the process of food chewing in preparation for ____ and ____.
swallowing and digestion.
How many pairs of muscles in the mandible make chewing movements possible?
There are four pairs
These muscles along with accessory ones together are termed as ____
MUSCLES OF MASTICATION
What are the “Basic Muscles”:
- lateral pterygoid
- medial pterygoid
- temporalis
- masseter
What are the “Accessory Muscles”:
- buccinator
- digastric muscle (anterior belly)
- mylohyoid
- geniohyoid
- orbicularis oris
Movements that the mandible can undergo are:
- Depression
- Elevation
- Protraction
- Retraction
- Rotation
as in opening the mouth.
Depression
as in closing the mouth.
Elevation
horizontal movement of the mandible anteriorly.
Protraction
horizontal movement of the mandible posteriorly.
Retraction
the anterior tip of the mandible is
“slewed” from side to side.
Rotation
the anterior tip of the mandible is
____ from side to side.
slewed
What are Jaw Elevators:
- Masseter
- Temporalis Medial pterygoid
- Upper head of lateral pterygoid
What are Jaw Depressors:
- Lower head of lateral pterygoid
- Anterior digastric
- Geniohyoid
- Mylohyoid
It is the largest among all the mastication muscles & is a fan-shaped muscle
Temporalis
Origin: from the inferior temporal line, floor of the temporal gossa and from the overlaying temporal fascia.
Temporalis
Insertion: anterior and medial tip of the coronoid process
Temporalis
Action: elevation (anterior fibers), retraction (posterior fibers)
Temporalis
Nerve supply: anterior division of the mandibular nerve
Temporalis
Origin: origin of the whole muscle is mainly from the zygomatic process
Masseter
Insertion: into the outer surface of the ramus of the mandible
Masseter
Action: mainly to elevate and also helps in protrusive movement
Masseter
Nerve supply: masseteric nerve, a branch of the anterior division of the mandibular nerve.
Masseter
Also called the Pterygoideus internus (internal pterygoid muscle)
Medial Pterygoid
Consists of 2 heads which differ in origin.
Origin: Deep Head and Superficial Head
Medial Pterygoid
originates from the medial surface of lateral pterygoid plate of the sphenoid bone.
Deep head
originates from the maxillary tuberosity
Superficial head
Insertion: inner surface of the angle of the mandible
Medial Pterygoid
Action: elevates the mandible, protrusion of the mandible, side to side movement (these lateral movements are achieved by lateral & medial pterygoid on both sides acting together to produce side to side movements)
Medial Pterygoid
Nerve supply: main trunk of the mandibular nerve
Medial Pterygoid
It is a short conical muscle, having 2 heads: upper and lower.
Lateral Pterygoid
Also called as the Pterygoideus externus (external pterygoid muscle)
Lateral Pterygoid
Nerve supply: anterior division of the mandibular branch of trigeminal nerve
Lateral Pterygoid
Actions:
1. Depression of the mandible
2. Side to side movement (lateral movement)
3. Protrusion of the mandible
Lateral Pterygoid
Origin: infra-temporal surface & crest of the greater wing of sphenoid
Upper Head
Insertion: temporomandibular joint and into: pterygoid fovea of the neck of the mandible, articular disc, capsule of TMJ (anterior aspect)
Upper Head
Origin: lateral surface of the lateral pterygoid plate
Lower Head
Insertion: same as that of the upper head,it enters
the TMJ and into:
1. Pterygoid fovea of the neck of the
mandible,
2. Articular disc
3. Capsule of TMJ (anterior aspect)
Lower Head
It is an accessory muscle of mastication
Buccinator
occupying the gap between mandible and maxilla forming part of the cheek.
Buccinator
Insertion:
1. Upper fibers gets inserted into upper lip
2. Lower fibers gets inserted into lower lip
Buccinator
Insertion:
1. Upper fibers gets inserted into ____
2. Lower fibers gets inserted into ____
- upper lip
- lower lip
Nerve supply: buccal branch of facial nerve
Buccinator
Action: main action is to prevent the accumulation of food in the vestibule of the mouth
Buccinator
Origin: arises from the digastric fossa on the lower border of mandible on both sides of symphysis menti
Anterior belly of digastric
Insertion: hyoid bone
Anterior belly of digastric
Nerve supply: through the anterior division of the mandibular branch of trigeminal nerve
Anterior belly of digastric
It forms the floor of the mouth
Mylohyoid
Action: main action is to depress the mandible
Anterior belly of digastric
Origin: mylohyoid line on the internal aspect of the mandible
Mylohyoid
Insertion: the fibers slops downward and forward to inter-digitate with the fibers of the other side to form the median raphe.
Mylohyoid
Nerve supply: mylohyoid nerve, a branch of inferior alveolar branch of mandibular nerve.
Mylohyoid
Action: elevates hyoid bone, supports and raises floor of the mouth which aids in early stage of swallowing, depresses the mandible
Mylohyoid
Origin: inferior genial tubercle
Geniohyoid
Insertion: hyoid bone
Geniohyoid
Nerve supply: hypoglossal nerve
Geniohyoid
Action: depresses the mandible
Geniohyoid
Encircles the mouth, closes lips, protrudes lips as in kissing, uniquely developed in humans for speech
Orbicularis Oris
Insertion: inserted in submucosa and dermis of the lips.
Orbicularis Oris
Nerve supply: facial nerve
Orbicularis Oris