Jaw

Question 1

What are the basic oral motor functions?

Answer 1

1. Ingestion - the ingestion of bolus of food - active lowering of the mandble, opening of the lips and depression of the tongue
2. Mastication - mechanical breakdown of food and mixing with saliva without damaging supportive tissue - facilitated by the masticatory apparatus
3. Deglutition
4. Communication/speech
5. Respiratory

Question 2

What parts of the body comprise the masticatory aparatus?

Answer 2

1. Teeth
2. Jaws
3. Masticatory muscles
4. TMJs
5. Tongue
6. Lips
7. Palate
8. Salivary glands

Question 3

What are the parts of the masticatory cycle?

Answer 3

1. Opening phase
2. Closing phase
3. Occlusal phase/power stroke

Question 4

What is the importance of mastication?

Answer 4

1. Digestion
2. Optimse the actions of the salivary enzymes
3. Sensation from taste buds
4. Detection of unwanted objects
5. Mental satisfaction
6. Plays a role in cognitive functions

Question 5

What are the primary muscles of mastication?

Answer 5

1. Masseter
2. Temporalis
3. Medial pterygoid
4. Lateral pterygoid

Question 6

What are the accessory muscles of mastication

Answer 6

Two groups:
1. Suprahyoids - digastric, mylohyoid, geniohyoid, stylohyoid
2. Infahyoids - thyrohyoid, sternohyoid, omohyoid

Question 6

What are the muscles involved in the up and down movements of the mandible?

Answer 6

Temporalis and masseter muscles

Question 7

What are the muscle involved in the side-to-side or grinding movements of the mandible?

Answer 7

Medial and lateral pterygoid

Question 8

What is a motor unit?

Answer 8

It is when several muscles fibres are innervated by a single motorneruon.

In the muscles of mastication have relatively fine control.

Question 9

What are receptors of the mastication?

Answer 9

1. Muscle spindles - spinned around intrafusal muscles - they are stimulated by stretch and cause a contraction of extrafusal fibres as a result of a reflex - monitor the of the muscles, their stretch and the speed of the stretch - involved in constant maintenance of mandible position - only available in jaw closer muscles
2. Tendon organ receptors - no specific info for orofacial area
3. Receptors in the TMJ - pain receptors, mechanoreceptors
4. Skin and mucosal receptors
5. Periodontal mechanoreceptors

Question 10

What are the basic components of the reflex arch?

Answer 10

1. Receptor - site of stimulus transduction
2. Sensory neuron - transmits afferent impulses to CNS
3. Integration centre - in the CNS
4. Motor neuron - conducts efferent impulses from the integration centre to an effector organ
5. Effector - muscle fibre or gland cell that produces response

Can be used to explain the jaw-closing reflex

Question 11

What is the jaw opening reflex?

Answer 11

It is a reflex that occurs due to instances of oral and perioral painful stimuli.

In humans, the JOR is essentially inhibition of jaw-closing muscles with little evidence for excitation of jaw opening muscles.

It plays a protective role in the mouth

Question 12

What is a periodontal reflex?

Answer 12

It is a reflex that is similar to the jaw opening reflex in terms of inhibiting the work of the jaw closer muscles - but it rather focuses on wear pressure thus it helps the jaw to keep food between the teeth.

Question 13

What is the peripheral input + cortical input + central pattern generator theory?

Answer 13

It is the most accepted theory that is used to explain mastication.

Essential the mastication occurs due to multiple factors and depend on the goal of mastication.

Question 14

What are the stages of swallowing?

Answer 14

1. Masticatory phase
2. Oral phase - voluntary pushing the bowlus from the oral cavity, by the tongue, into the oroharynx
3. Pharyngeal phase - respiration inhibition, elevation of soft palate to seal nasal cavity, glottis closes and seal entrance to trachea, involuntary control occurs
4. Oesophageal phase - oesophagela sphincter open and parastatic movement move the bolus down

Question 15

What are the three components of swallowing control?

Answer 15

1. Sensory input - from the oral cavity, pharynx, larynx and oesophagus
2. Interneuronal network - located in the ventral and dorsal regions of the medulla
3. Motor output

Question 16

What is gag reflex?

Answer 16

It is an uleasant, spasmodic and abortive respiratory movement with the glottis closed.

Can be triggered by mechanical stimulation initially, later, due to conditioning, may be cause by psychological factors.

Gagging need to be inhibited by appropriate training.

Question 17

What is the digastric muscle and what does it do?

Answer 17

They are two fleshy bellies united by a cylindrical intermediate tendon

They play a role in jaw opening

Question 18

What is the mylohyoid muscles and what does it do?

Answer 18

It is the muscle that forms the floor of the mouth.

It is similar in function to digastric muscles - meaning it pays a role in jaw opening - but it also plays a role in tongue movement

Question 19

What is the function of temporalis muscle and what is ti associated with?

Answer 19

The function of the temporalis muscle is to elevate and retract the mandible at TMJ to close the jaw.

The temporalis is commonly associated with TMD and also has trigger points for bruxism and teeth clenching

Question 20

What is the function of the lateral pterygoid muscle and what is it associated with?

Answer 20

Plays an important role in control of jaw movement and has two head

1. Inferior head - involved with jaw opening, jaw protrusion and contralateral jaw movements
2. Superior head - similar function

Both head should be seen as one unit

Question 21

What is the function of medial pterygoid muscle and what is it associated with?

Answer 21

Elevation of the mandible

Assisting the laterl pterygoid in moving the jaw from side to side.

Associated with trismus!!!!!!!

Question 22

What is the function of the masseter muscle and what is it associated with?

Answer 22

It is active in inhibiyion of jaw closing during incisal clenching

Question 23

What are the three main types of muscle fibres and what are they used for?

Answer 23

1. MyHC-I isoform - aerobic, slow contractin and slow to fatigue, tonic contractions
2. MyHC-II isoform - anaerobic, fast contracting, quick to fatigue, power contractions
3. Hybdrid fibre (meaning differen MyHC present) - very fine gradation of force and movement - IMPORTNAT FOR MUSCLE OF MASTICATION, high proportion is orofacial area

Question 24

What are some factors that affect fibre-type composition?

Answer 24

1. Activity 2. Age 3. Sex 4. Diet

Question 25

How do muscle respond to alteration in the oral cavity?

Answer 25

Muscle of theorofacial region can adapt to new functional needs due to muscular plasticity. That concept is used in tooth extractions, surgical intervention and orthodontic interventions.