Final answer:
The cheeks form the walls of the oral cavity, while the lips encompass its opening. Inside, the oral cavity features areas like the oral vestibule and the fauces and includes the hard and soft palates, which allow simultaneous digestion and respiration.
Step-by-step explanation:
The cheeks form the walls of the oval-shaped oral cavity and the lips surround the opening to the cavity. Within the oral cavity, various structures contribute to its function in digestion and speech. The cheeks, composed of buccinator muscles and non-keratinized, stratified squamous epithelium, make up the sidewalls of the oral cavity.
The lips, with their underlying orbicularis oris muscle, help regulate the entrance and exit of materials in the mouth and also play a key role in speech and facial expressions. The oral cavity proper extends from the gums and teeth to the fauces, acting as the primary space for food intake and initial digestion, while the oral vestibule is the pocket-like part of the mouth between the cheeks, lips, gums, and teeth.
The hard and soft palates form the roof of the mouth, dividing the oral from the nasal cavity, and facilitating both digestion and respiration. The oropharynx serves as a passageway for air and food, containing lymphoid tissue that functions in immune response. Together, these components of the oral cavity play critical roles in maintaining oral health and facilitating essential functions such as eating, breathing, and speaking.