Mastication, TMJ and Swallowing Flashcards Preview

Sc 23 - Head and neck Neuroanatomy > Mastication, TMJ and Swallowing > Flashcards

Flashcards in Mastication, TMJ and Swallowing Deck (25):

Infratemporal fossa

- wedge shaped

- lies inferior to the temporal fossa

Major Contents:

  • Sphenomandibular Ligament
  • Medial & Lateral Pterygoid muscles
  • Maxillary artery
  • Mandibular nerve - CN V3
  • Branches of Facial nerve - CN VII
  • Glossopharyngeal nerve CN IX
  • Pterygoid plexus of veins



Infratemporal fossa

  • Main things to know that is within here
  • Nerves + vasculature


Branches of the Mandibular Division (V3) of the Trigeminal nerve and the Maxillary Artery

  1. Inferior alveolar nerve
  2. Nerve to Mylohyoid
  3. Lingual Nerve
  4. Buccal nerve

N.B. The Maxillary artery is a branch of the External Carotid Artery


Pterygoid Plexus of Veins


What is it and what is the risk here?

  • Communicates with retromandibular and facial veins
  • Possible route of infection:
    • Infection can travel through here as the veins in the head and neck don't have valves to stop them progressing



  • process initiated by movement of the lower jaw:-
    • ​Possibly since there is a synovial joint btwn the mandible and the temporal bone
  • Movement here allows teeth to function in biting and grinding food
  • Muscles of the tongue act to keep the food between the molars



Temporomandibular Joint  (TMJ)

  • Articuar disc divides joint into upper & lower cavities
    • Provides extra movement
      • TMJ = simple hinge + sliding joint


Types of Movement at the TMJ


Presence of the articular disc in the joint cavity allows more than one type of movement


  • ​Takes place in the LOWER COMPARTMENT between the stationary disc and the moving condyle


  • Takes place in the UPPER COMPARTMENT between the moving disc and the stationary fossa

Lateral temperomandibular ligament - the strongest ligament at the joint


6 basic movements of the Mandible

Produced when the gliding and hinge movements are combined

  • Elevation
  • Depression
  • Lateral excursions (both left and right)
  • Protrusion
  • Retrusion


Muscles of Mastication

4 major ones

Supplied by the mandibular division (V3) of the Trigeminal nerve

  1. Massester
  2. Temporalis
  3. Medial Pterygoid
  4. Lateral Pterygoid

N.B. Also a number of minor masticatory muscles

- e.g. the superior and inferior hyoid muscles



Masseter Muscle

Double headed - has 2 origins


  1. Zygomatic Arch
  2. Mandible
  • Muscle is qualrilateral in shape
  • Covers most of the ramus of the Mandible
    • Superficial fibres: are oblique
    • Deep fibres: vertical in orientation


Actions of the Masseter Muscle

  1. Elevation:
    • ​​using both massester muscles - powerful elevation of mandible = clenched teeth
  2. Retrusion
    • using both mass. muscles, deep fibres help retrude a protruded Mandible
  3. Ipsilateral Rotation
    • ​​single masseter can move the Mandible side to side

N.B.: All work together to provide normal movement




Fan shaped muscle


Attaches to side of skull and the coronoid process of the mandible

Insertion by the 3rd lower molar

Muscle arises from 2 heads:

  1. Attached to the Temporal bone
  2. Arises from the Temporal Fascia


Actions of Temporalis

  1. Resting Tonus
    • ​​Maintain the normal mandibular rest position (i.e. closed mouth) when the subject is in the upright position
  2. Elevation
    • ​​Fibres of both sides are active esp in biting
  3. Retrusion
    • ​​Posterior Horizontal Fibres of both sidesd retrude the protuded Mandible
  4. Ipsilateral Excursion
    • ​Acting one side only, temporalis is capable of pulling Mandible to the same side


Medial & Lateral Pterygoid Muscles

  • Occupy the Infratemporal Fossa

Have to remove a portion of the Mandible to see the muscles


medial pterygoid muscle:

  • Mirror of the Masseter Muscle on the inner surface of the Mandible

lateral pterygoid muscle:

  • almost triangular in shape
  • Only muscle of Mastication to lie horizontally


Actions of the 

Medial Pterygoid Muscle

  1. Elevation
    • ​​Acting together, med ptery along with Masset are powerful elevators of the jaw
  2. Protrusion
    • ​​Together the right and left muscles aid in protrusion of the jaw
  3. Contralateral Excursion
    • ​​Muscle from one side, the med ptery moves the jaw to the opp side


Actions of the

Lateral Pterygoid Muscle

  1. Protrusion
    • ​​Acting together the lat ptery are the prime protractors of the mandible
    • Horizontal fibes pull the mandible forward onto the articular disc
  2. Depression
    • ​​Contraction of both muscles pull the jaw forwards  
    • also with hyoid muscles help depress the jae
  3. Contralateral Excursion
    • ​​Singly the lat ptery moves the Mandible in the opposite direction


Hyoid Muscles:

Always contract bilaterally.

Infrahyoid muscles: depress the hyoid bone and larynx during swallowing

Suprahyoid muscles: form the floor of the mouth.

- Act to raise the hyoid bone and larynx when the mandible is stabilised

Can also act with the infrahyoid and lat ptery to depress the mandible

Infrahyoid Muscles:

  • Stylohyoid
  • Digastric 
  • Mylohyoid
  • Geniohyoid

Suprahyoid Muscles:

  • Omohyoid 
  • Sternohyoid 
  • thryohyoid
  • Sternothyroid


What is Ptylain?

An amylase that begins the breakdown of carbohydrates


What is the mechanism by which breathing is allowed whilst chewing by preventing food entering the airstream?

Bilateral contraction of the palatoglossus muscles narrow the OROPHARYNGEAL ISTHMUS

the posterior part of the tongue fills the remainder of the gap


What does relaxation of the palatoglossal muscles cause?

Opening of the Oropharyngeal isthmus



Takes 2 seconds from oropharynx to stomach

  • As bolus reaches oropharynx, soft palate is made taught by tensor muscles & raised by the levator muscles
  • Superior constrictor also contracts, closing the nasopharynx from the oropharnyx
  • Larynx simulataneously is raised and brough forward by action of suprahyoid muscles, esp Geniohyoid and Ant belly of Digastric, to sit under the tongue, forcing epiglottis over the laryngeal opening
  • Epiglottis - acts as a deflector 
  • Middle and inf constrictors contract, pushing bolus into the oesophagus continuing peristalitic contraction
  • Aryepiglotic and Transvers arytenoid muscles contract reducing the size of the laryngeal inlet. Vocal and vestibular folds also close
  • As food enters the oesophagus, the muscles relax and the hyoid bone and larynx return to their original position, upon which breathing can then resume




Begins as a voluntary movement but proceeds involuntarily once it has begun


1) Buccal Phase of Swallowing

Compression of bolus against the hard palate and elevation of the soft palate


2) Pharyngeal phase of Swallowing

Bolus comes into contact with the Pharyngeal wall. Larynx is elevated and the muscles propel the bolus towards the oesophagus.


3) Oesophageal phase of Swallowing

Oesophageal sphincter opens and bolus is pushed into it



what do the intrinsic and extrinsic muscles of the larynx prevent?

They prevent food or drink entering the glottis during swallowing