Oral preparatory phase Flashcards
what happens in the oral preparatory phase?
Food:
- enters the oral cavity
- is sealed within the oral cavity
- is ground up and mixed with saliva to form a bolus
This phase is under voluntary control, but can be performed automatically
anterior and lateral borders of the oral cavity
the alveolar process of the maxilla and the upper teeth superiorly, the mandible and the lower teeth inferiorly
Facial muscles - which are used, and what CN are they innervated by?
Obicularis oris and risorius - close and tense the lips
Buccinator - maintains tension in the cheeks
Innervated by the facial nerve (CNVII)
What is dental occlusion, and what can problems with dental occlusion cause?
The way the upper and lower teeth meet when the jaws bite together
Problems can cause difficulty with biting and chewing food (could be caused by poorly fitting dentures, overbite, underbite, crossbite, open bite)
The TMJ: what is it and what movement does it enable?
The temporomandibular joint (synovial joint between the condylar process of the mandible and the mandibular fossa of the temporal bone
Rotation of the condylar process in the mandibular fossa (lower joint compartment) causes the mouth to open and close
Gliding movements of the mandibular condyle (upper joint compartment) causes the jaw to protrude and retract
Lateral movement of lower jaw relative to upper jaw enables chewing and grinding
Masseter
Masseter: elevates and protrudes mandible (closes mouth)
Which muscles close the mouth?
Masseter (up and forward), temporalis (up and back) and medial pterygoid (up and forward)
Key constituents of saliva
Water (99.5%)
Electrolytes (salts)
Digestive enzmes (e.g. amylase)
Antimicrobial enzymes that kill bacteria
Key functions of saliva
- moistening consistency of food to aid bolus formation and transit
- lubrication of oral mucosa to prevent damage
- initiating digestion of food components
- providing liquid medium to transport food molecules to taste receptors
- maintenace of oral hygiene
Intrinsic muscles of the tongue - vertical, transverse and longitudinal (superiro and inferior)
Vertical: flatten and widen tongue
Transverse: elongate and narrow tongue
Superior longitudinal: tip of tongue upwards
Inferior longitudinal: tip of tongue downwards
Extrinsic muscles of the tongue and innervation
palatoglossus, styloglossus, hyoglossus, genioglossus
All inervated by hypoglossal nerve except palatoglossus which is innervated by the vagus nerve
palatoglossus
elevates posterior part of tongue and depresses soft palate
styloglossus
elevates and retracts tongue
hyoglossus
depresses and retracts tongue
Genioglossus
protrudes the tongue
What does the tongue do in the oral preparatory phase?
moves the food around the mouth during mastication, e.g.
- directing between grinding surface of teeth, clearing ressidue from buccal cavity and around teeth
roof of the oral cavity
hard and soft palate, uvula
floor of the oral cavity
some of they suprahyoid muscles, largely occupied by tongue
posterior boundary of the oral cavity
the fauces (arched folds of tissue at the anterior end of the oropharynx)
Temporalis
anterior fibres elevate the mandible, posterior fibres retract the mandible (closes the mouth)
Medial pterygoid
bilateral contraction elevates and protrudes the mandible (closes the mouth)
unilateral contraction of medial and lateral pterygoid moves the mandible sideways for chewing
Lateral pterygoid
Lateral pterygoid: bilateral contraction depresses and protrudes the mandible (opens the mouth)
unilateral contraction of medial and lateral pterygoid moves the mandible sideways for chewing
