Mastication (Chewing)

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  • Created by: SamDavies
  • Created on: 23-04-18 23:18

Functions of Chewing

  • Mash and crush food to create a bolus that is small enough to swallow. This aids digestion
  • Mix food with saliva
  • Increase surface area for enzymes such as amylase

This involves moving the mandible (jaw bone) up and down to allow the incisors to bite the food and moving it side to side so the molars can crush the food into a bolus. The tongue then moves to allow the swallowing of the bolus

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Muscles Involved

The muscles involved in jaw closing:

  • Temporalis
  • Masseters
  • Medial pterygoid

The muscle involved in jaw opening:

  • Lateral pterygoid

 (http://www.medicalestudy.com/wp-content/uploads/2016/07/MasticationMuscles.jpg)

The movement of these muscles is innervated by cranial nerve V trigeminal (5th )

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Control of Chewing (1)

Chewing is under both voluntary control and sensory control
The CPG (central pattern generator) or chewing centre is a network of neurones in the brainstem that can control both jaw movements (i.e. opening and closing) and force of bite.

Voluntary control

  • The cortex, which controls voluntary movement, sends signals to the chewing centre which brings about an appropriate response/effect
  • Cortex è chewing centre è effector

Sensory control

  • There are sensory nerves within the teeth which can also relay information to the chewing centre to bring about a response
  • Sensory nerves è chewing centre è effector

This control is important because we can adapt our responses to food type (e.g. hard or soft foods) so that we prevent excessive force being applied to the tooth.

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Control of Chewing (2)

The masticatory CPG is composed of two groups of neurones:

  • Rhythm generator: generates the basic masticatory rhythm
  • Burst generator: adapts the rhythm according to sensory inputs from the oral cavity so that the movement becomes appropriate for the food bolus, size, viscosity and temperature

Mastication is somewhat a reflex mechanism because the CGP automatically initiates and maintains jaw opening/closing without conscious input. We don't have to think about which muscles to activate and the timing of activation. However, this is still under our voluntary control.

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