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

Mastication, TMJ and Swallowing Flashcards

1
Q

Infratemporal fossa

  • wedge shaped
  • lies inferior to the temporal fossa
A

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
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2
Q

Infratemporal fossa

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

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

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3
Q

Pterygoid Plexus of Veins

What is it and what is the risk here?

A
  • 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
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4
Q

Mastication

A
  • 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
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5
Q

Temporomandibular Joint (TMJ)

A
  • Articuar disc divides joint into upper & lower cavities
    • Provides extra movement
      • TMJ = simple hinge + sliding joint
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6
Q

Types of Movement at the TMJ

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

A

Hinge:

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

Gliding:

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

Lateral temperomandibular ligament - the strongest ligament at the joint

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7
Q

6 basic movements of the Mandible

Produced when the gliding and hinge movements are combined

A
  • Elevation
  • Depression
  • Lateral excursions (both left and right)
  • Protrusion
  • Retrusion
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8
Q

Muscles of Mastication

4 major ones

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

A
  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
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9
Q

Masseter Muscle

Double headed - has 2 origins

A

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
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10
Q

Actions of the Masseter Muscle

A
  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
    • ​​a single masseter can move the Mandible side to side

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

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11
Q

Temporalis

Fan shaped muscle

A

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
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12
Q

Actions of Temporalis

A
  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
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13
Q

Medial & Lateral Pterygoid Muscles

  • Occupy the Infratemporal Fossa

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

A

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
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14
Q

Actions of the

Medial Pterygoid Muscle

A
  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
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15
Q

Actions of the

Lateral Pterygoid Muscle

A
  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
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16
Q

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*
A

Infrahyoid Muscles:

  • Stylohyoid
  • Digastric
  • Mylohyoid
  • Geniohyoid

Suprahyoid Muscles:

  • Omohyoid
  • Sternohyoid
  • thryohyoid
  • Sternothyroid
17
Q

What is Ptylain?

A

An amylase that begins the breakdown of carbohydrates

18
Q

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

A

Bilateral contraction of the palatoglossus muscles narrow the OROPHARYNGEAL ISTHMUS

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

19
Q

What does relaxation of the palatoglossal muscles cause?

A

Opening of the Oropharyngeal isthmus

20
Q

Swallowing

Takes 2 seconds from oropharynx to stomach

A
  • 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
21
Q

Swallowing

A

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

22
Q

1) Buccal Phase of Swallowing

A

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

23
Q

2) Pharyngeal phase of Swallowing

A

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

24
Q

3) Oesophageal phase of Swallowing

A

Oesophageal sphincter opens and bolus is pushed into it

25
Q

Swallowing

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

A

They prevent food or drink entering the glottis during swallowing

Sc 23 - Head and neck Neuroanatomy (10 decks)

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