# 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 . - **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. | Enzyme | Also Known As | Substrate (What it acts on) | Products | | :--- | :--- | :--- | :--- | | **Salivary Amylase** | Ptyalin | Starch (a polysaccharide) | Maltose, Maltotriose, Isomaltose (smaller sugars) | | **Lingual Lipase** | - | Triglycerides (fats) | Diacylglycerols and Monoacylglycerols |