1.1 Oral Cavity

The primary structures and digestive processes that begin in the oral cavity (buccal cavity), focusing on both the physical breakdown and initial chemical breakdown of food.

Structure of the Oral Cavity

The oral cavity, or buccal cavity, is the entry point of the digestive system. Its main components are:

• Lips and Cheeks: Surround the oral cavity.
• Tongue: A muscular organ involved in manipulating food for chewing and swallowing.
  • Its surface contains rough projections called papillae, which create friction for handling food.
  • Papillae also house the taste buds, responsible for the sense of taste.
  • The tongue acts as a sensory organ. For more on how receptors work, see Receptors Are Transducers→.
• Palate: Forms the roof of the oral cavity, separating it from the nasal cavity.
• Teeth: Adapted for handling food in different ways (e.g., cutting, tearing, grinding).
• Salivary Glands: Three pairs of glands that secrete saliva into the oral cavity. Saliva contains enzymes that initiate chemical digestion.

Digestion in the Oral Cavity

Both mechanical and chemical digestion begin in the mouth.

Mechanical Digestion

• Definition: The physical breakdown of large food pieces into smaller ones.
• Process: Achieved through mastication (chewing) by the teeth.
• Purpose:
  1. To break down tough coverings like the cellulose in plant-based foods.
  2. To significantly increase the surface area of the food, allowing digestive enzymes to act more efficiently.

Chemical Digestion

• Definition: The chemical breakdown of complex food molecules into simpler ones by enzymes.
• Process: Saliva, secreted by salivary glands, mixes with the food. Saliva contains two key digestive enzymes.
• Outcome: The combination of mechanical and chemical digestion forms a soft, oval mass of food called a bolus, which is then swallowed.