Final answer:
The oral stage of swallowing (voluntary phase) is true to last approximately 1 second for liquids and very soft foods. This voluntary action initially moves the food into the oropharynx before the involuntary phases of swallowing take over.
Step-by-step explanation:
The statement The oral stage of swallowing is a voluntary stage lasting approximately 1 second is true for very soft food and liquids. The voluntary phase or the oral stage of deglutition is where the swallowing process begins, and we can control when to swallow the food. Once chewing is completed, the tongue moves upward and backward against the palate, pushing the bolus towards the back of the oral cavity and subsequently into the oropharynx. This initial phase is followed by two involuntary phases: the pharyngeal phase and the esophageal phase, which are controlled by the autonomic nervous system. The pharyngeal phase involves the upward movement of the soft palate and uvula to prevent food from entering the nasopharynx, and the constriction of the laryngeal muscles to avoid aspiration of food into the trachea. Lastly, during the esophageal phase, peristalsis moves the bolus through the esophagus to the stomach. The duration of the entire process of swallowing, from mouth to stomach, ranges from 4 to 8 seconds for solid or semisolid food, and about 1 second for very soft food and liquids.