Mastication
Mastication is the fancy word for chewing.
What's the point of chewing?
This may seem like a silly question but there are different reasons we chew instead of just swallowing all foods whole...
How does it work?
So chewing isn't just the result of closing your teeth over and over on a piece of food. Bite force and muscles are necessary components to sufficiently break down the food. Another integral part is the tongue. The tongue is constantly manipulating the bolus throughout mastication and making sure the bolus stays between the teeth. The tongue plays a much larger part in chewing and swallowing then people realize!
- It's the process whereby by ingested food (food you've put into your mouth) is cut or crushed into small pieces mixed with saliva and formed into a bolus* in preparation for swallowing
What's the point of chewing?
This may seem like a silly question but there are different reasons we chew instead of just swallowing all foods whole...
- Chewing enables the food bolus to be easily swallowed (decreases chances of choking/gagging)
- Chewing enhances the digestibility of food
- Chewing mixes food with saliva which initiates digestion (by the activity of salivary amylase)
- Chewing prevents irritation of the GI system by large food masses
- Chewing ensures healthy growth and development of the oral tissues
- Chewing increases digestive efficiency
How does it work?
So chewing isn't just the result of closing your teeth over and over on a piece of food. Bite force and muscles are necessary components to sufficiently break down the food. Another integral part is the tongue. The tongue is constantly manipulating the bolus throughout mastication and making sure the bolus stays between the teeth. The tongue plays a much larger part in chewing and swallowing then people realize!
Mastication is dependent upon a complex chain of events. The rhythmic opening and closing movements of the jaws by a series of muscles needs to be correlated to tongue movements.
The teeth and jaws exert a powerful force referred to as bite force. This is the force that is exerted on food during mastication. The amount of force will vary according to the texture and quantity of food.
Their is no set amount of "chews" a person needs to do before swallowing. The amount of chewing before initiating a swallow varies based on the characteristics of the individual and is influenced by the nature of the food.
Their are 3 basic phases in the chewing cycle:
Mastication involves prolonged bursts of muscle activity.
The teeth and jaws exert a powerful force referred to as bite force. This is the force that is exerted on food during mastication. The amount of force will vary according to the texture and quantity of food.
Their is no set amount of "chews" a person needs to do before swallowing. The amount of chewing before initiating a swallow varies based on the characteristics of the individual and is influenced by the nature of the food.
Their are 3 basic phases in the chewing cycle:
- The jaw is open and the first "chew" happens is the closing stroke where the teeth have their first initial contact with the food and the work being done in this phase is against gravity
- When the food begins to get reduced is the power stroke; the jaw movement is slower than in the closing stroke because of the resistance being caused by the food, even though there will be a lot of muscle activity during this time
- Lastly, when the jaw is lowered, with an initial slower stage followed by a faster stage is the opening stroke.
Mastication involves prolonged bursts of muscle activity.
Jaw Patterns
Normal Jaw Patterns
It is important to note that these patterns do not develop in order. In the same person, more mature patterns could be observed with easy to chew foods and more primitive patterns with harder to chew items.
It is important to note that these patterns do not develop in order. In the same person, more mature patterns could be observed with easy to chew foods and more primitive patterns with harder to chew items.
- Mature patterns:
- are used with foods requiring grinding
- Primitive patterns:
- are used with less viscous foods
- primitive patterns do not disappear
- Close and hold
- Jaw stability and strength are adequate to close around the item with normal muscle tone, but not yet strong enough to allow up and down jaw movement around the item.
- Wide jaw excursion
- This is an early pattern characterized by poor jaw grading where downward jaw displacement is exaggerated. It is associated with poor internal jaw stability. This can occur during suckling, sucking, and chewing. It is seen most during nursing and then again later when cup drinking is first introduced.
- Phasic biting
- A primitive normal jaw pattern characterized by rapid rhythmical up and down movement of the jaw. No lateral movement of the jaw (side to side movement). It is limited in power.
- Nonstereotypical vertical movements
- A beginning chewing pattern, the jaw moves up and down with easy contact and release. Only vertical movement has developed, so that only food coming between the teeth is broken up.
- Munching
- An early chewing pattern that combines phasic biting and some nonstereotypic vertical movements of the jaw with tongue movement to the hard palate. No lateral jaw movement is observed.
A person with these above 5 patterns would not be able to grind fibrous foods. There is still no lateral jaw movement. Soft, lumpy foods and ground meats are usually the diet tolerated.
- An early chewing pattern that combines phasic biting and some nonstereotypic vertical movements of the jaw with tongue movement to the hard palate. No lateral jaw movement is observed.
- Lateral jaw shift
- This is a lateral (side to side) movement of the jaw with no downward displacement of the jaw
- Diagonal movement
- This is a lateral, downward movement of the jaw to either side with easy contact and release. It aids in the placement of food between molars for chewing. There is no grinding movement and no movement of the jaw across midline. It occurs with vertical jaw movement.
- Diagonal rotary movement
- This is a lateral downward movement with upward horizontal sliding movements for grinding foods between molars. The jaw moves to one side or the other without crossing midline. It may also have lateral movement of food from the center of the tongue to the teeth.
- Circular rotary movement
- This is the most mature chewing pattern, with jaw movement laterally, downward across the midline to the other side and upward to close. It may occur either clockwise or counter-clockwise. It may have transfer of food from one side of the mouth across the midline to the other side of the mouth. Each of these patterns may be accompanied by significant muscle weakness. The pattern is observed, but is not efficient for more viscous foods due to lack of power for closing the jaw.
Abnormal Jaw Patterns
Abnormal jaw patterns can interfere with eating, drinking, and speech. Controlled movement of the cheeks, lips, and tongue is also adversely affected by abnormal jaw patterns. When these are present, mealtimes take longer. There will be poor control of items placed in the mouth leading to loss of foods, fluids, medications and saliva. Oral hygiene becomes difficult to provide resulting in dental problems.
Abnormal:
Abnormal jaw patterns can interfere with eating, drinking, and speech. Controlled movement of the cheeks, lips, and tongue is also adversely affected by abnormal jaw patterns. When these are present, mealtimes take longer. There will be poor control of items placed in the mouth leading to loss of foods, fluids, medications and saliva. Oral hygiene becomes difficult to provide resulting in dental problems.
Abnormal:
- Jaw clonus
- Rapid, rhythmical movement of the jaw upon closure, indicating weakness or fatigue. May be observed in infants during sucking
- Rapid, rhythmical movement of the jaw upon closure, indicating weakness or fatigue. May be observed in infants during sucking
- Tonic bite reflex
- This is jaw closure accomplished by forceful, sustained upward movement of the jaw. Increased abnormal tone in the jaw muscles. It is difficult to release. Damage to the teeth or to the object placed in the mouth may occur. The tonic bite increases if the item is pulled on.
- This is jaw closure accomplished by forceful, sustained upward movement of the jaw. Increased abnormal tone in the jaw muscles. It is difficult to release. Damage to the teeth or to the object placed in the mouth may occur. The tonic bite increases if the item is pulled on.
- Jaw thrust
- The jaw opens through forceful, sustained downward and outward movement of the jaw. It occurs following presentation of food for biting. Can also occur as part of a total body extension pattern. Increased abnormal tone in jaw muscles. Pressing up on the jaw increases the jaw thrust.
- The jaw opens through forceful, sustained downward and outward movement of the jaw. It occurs following presentation of food for biting. Can also occur as part of a total body extension pattern. Increased abnormal tone in jaw muscles. Pressing up on the jaw increases the jaw thrust.
- Jaw retraction
- Forceful, sustained movement of the lower jaw, carrying it up and towards the back so that the alignment of the molars is displaced. It is associated with an abnormal increase in jaw muscle tone. It can occur after change in body position or following the presentation of foods/liquids/or meds into the mouth. There is less room in the back of the mouth so swallowing and breathing are more difficult.
- Forceful, sustained movement of the lower jaw, carrying it up and towards the back so that the alignment of the molars is displaced. It is associated with an abnormal increase in jaw muscle tone. It can occur after change in body position or following the presentation of foods/liquids/or meds into the mouth. There is less room in the back of the mouth so swallowing and breathing are more difficult.
- Dystonic jaw movement
- Characterized by rhythmical, nonfunctional movement of the jaw associated with Parkinson's or Parkinson's like symptoms. The ability to interrupt the movement is related to the severity of the disease. With less severe, the pattern can be interrupted during functional activities like eating and speech and will not be observed during sleep
- Characterized by rhythmical, nonfunctional movement of the jaw associated with Parkinson's or Parkinson's like symptoms. The ability to interrupt the movement is related to the severity of the disease. With less severe, the pattern can be interrupted during functional activities like eating and speech and will not be observed during sleep
- Bruxism
- Also known as toothgrinding, can occur for a variety of reasons. Can be associated with muscle weakness or with abnormally increased muscle tone. Pressure to the outside of the face is not effective in reducing this. Emphasize on increased internal jaw stability with opportunities for closing molars around chewy objects. Bruxism can increase when an ear infection or fluid in the middle ear is present. It can also increase with headaches or pain due to gum/tooth disease.
- Also known as toothgrinding, can occur for a variety of reasons. Can be associated with muscle weakness or with abnormally increased muscle tone. Pressure to the outside of the face is not effective in reducing this. Emphasize on increased internal jaw stability with opportunities for closing molars around chewy objects. Bruxism can increase when an ear infection or fluid in the middle ear is present. It can also increase with headaches or pain due to gum/tooth disease.
The tongue
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The tongue has four primary functions:
The tongue has two types of muscles: |
What is the tongue?
It is an extremely movable set of muscles with the root of the tongue anchored to the floor of the mouth, and the other parts of the tongue can freely move. A strip of tissue called the lingual frenulum connects the underside of the tongue to the floor of the mouth. When you close your mouth, your tongue almost fills up the entire space of your mouth. |
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Extrinsic muscles:
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Intrinsic muscles:
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Let's focus on the extrinsic muscles' responsibilities as they are the ones crucial to feeding.
The tongue's jobs:
The tongue's jobs:
- Eating and drinking
- The tongue's main job is helping us to eat. It allows us to suck and turn solid food into a mash that can be swallowed. The tongue also initiates the act of swallowing. The tongue differentiates tastes and flavors.
- The tongue's main job is helping us to eat. It allows us to suck and turn solid food into a mash that can be swallowed. The tongue also initiates the act of swallowing. The tongue differentiates tastes and flavors.
- Sucking
- The tongue is vital for babies when breastfeeding. When the mouth latches on and the lips form a tight seal the oral cavity becomes a cylinder. The tongue moves backward in the closed mouth producing low pressure which sucks in fluid for drinking.
- The tongue is vital for babies when breastfeeding. When the mouth latches on and the lips form a tight seal the oral cavity becomes a cylinder. The tongue moves backward in the closed mouth producing low pressure which sucks in fluid for drinking.
- Chewing, grinding, pressing, salivating
- When we chew, the tongue and cheeks work together to constantly move the food between the teeth so that it can be chewed. The tongue presses the crushed food against the palate and moves the bolus to the throat when it is ready to be swallowed. The movement of the tongue also massage small glands directly underneath it to squeeze out saliva which is used to create the bolus and break down food. This also starts pre-digestion of the food and the bolus can glide down the esophagus (food tube) more easily.
- When we chew, the tongue and cheeks work together to constantly move the food between the teeth so that it can be chewed. The tongue presses the crushed food against the palate and moves the bolus to the throat when it is ready to be swallowed. The movement of the tongue also massage small glands directly underneath it to squeeze out saliva which is used to create the bolus and break down food. This also starts pre-digestion of the food and the bolus can glide down the esophagus (food tube) more easily.
- Swallowing
- The tongue will press the bolus into the throat, during that backward movement the tongue initiates the swallow mechanism which will lower the epilgottis and prepare the throat for the bolus
- The tongue will press the bolus into the throat, during that backward movement the tongue initiates the swallow mechanism which will lower the epilgottis and prepare the throat for the bolus
- Tasting
- The tongue's mucous membrane contains many taste receptors to test the things we eat and drink. These are found in the taste buds.
- The tongue's mucous membrane contains many taste receptors to test the things we eat and drink. These are found in the taste buds.
