The mechanism of mastication, or chewing, involves both vertical and horizontal (side-to-side) movements of the jaw that crush and break down food into smaller fragments suitable for swallowing, while simultaneously mixing it with saliva.
Here's a more detailed breakdown:
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Food Intake: The process begins with food entering the mouth.
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Jaw Movements: Mastication relies on coordinated movements of the mandible (lower jaw).
- Vertical Movements: Primarily involve opening and closing of the mouth. These movements allow the teeth to initially bite and begin breaking down the food.
- Horizontal (Lateral) Movements: Side-to-side grinding actions are crucial for effective crushing and shearing of food, especially by the molars.
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Role of Teeth: Different types of teeth contribute to the process:
- Incisors: Used for initial biting and cutting of food.
- Canines: Help in tearing food.
- Premolars & Molars: Primarily responsible for grinding and crushing food into smaller particles.
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Saliva Secretion: Salivary glands release saliva, which contains:
- Amylase: An enzyme that begins the chemical breakdown of carbohydrates.
- Mucus: Lubricates the food, facilitating easier swallowing and bolus formation.
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Muscles Involved: Several muscles are involved in mastication:
- Masseter: Elevates the mandible (closes the jaw).
- Temporalis: Elevates and retracts the mandible.
- Medial Pterygoid: Elevates and protrudes the mandible, contributing to lateral movements.
- Lateral Pterygoid: Depresses and protrudes the mandible, also contributing to lateral movements.
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Sensory Feedback: Sensory receptors in the mouth provide feedback about the texture, size, and consistency of the food, influencing the masticatory movements.
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Bolus Formation: Through chewing and mixing with saliva, the food is formed into a soft, cohesive mass called a bolus.
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Swallowing: Once the bolus is formed, it is ready for swallowing, initiating the process of deglutition.
In essence, mastication is a complex process that utilizes the coordinated action of jaw muscles, teeth, and saliva to reduce food particle size, lubricate the food, and initiate digestion, preparing it for swallowing and further processing in the digestive system.
