The oral stage of swallowing encompasses both the preparation of food in the mouth and its movement to the back of the mouth in preparation for the pharyngeal swallow. It has two sub-phases: the oral preparatory phase and the oral transit phase.
Oral Preparatory Phase
This phase is crucial for preparing the bolus (the mass of food to be swallowed). Key aspects include:
- Mastication (Chewing): The food is broken down into smaller pieces through chewing.
- Salivation: Saliva mixes with the food, helping to soften it and begin the digestive process.
- Bolus Formation: The chewed food mixes with saliva to form a cohesive bolus of suitable size and consistency. This is a rounded mass ready for swallowing.
- Sensory Feedback: Sensory receptors in the mouth provide feedback on the bolus's size, texture, and consistency, allowing for adjustments in chewing and saliva production.
Oral Transit Phase
This phase involves moving the prepared bolus from the front of the mouth to the back, triggering the swallow reflex.
- Tongue Action: The tongue elevates and retracts, propelling the bolus towards the pharynx (throat).
- Soft Palate Elevation: The soft palate elevates to close off the nasal cavity, preventing food from entering the nose.
- Pharyngeal Swallow Initiation: As the bolus reaches the back of the tongue, it triggers the pharyngeal phase of swallowing.
- Duration: This phase is relatively short, typically lasting about one second.
In summary, the oral stage of swallowing is an active process involving chewing, salivation, bolus formation, and controlled movement of the bolus to the back of the mouth, setting the stage for the pharyngeal phase of swallowing.
