Digestion Begins in the Mouth: Mechanical and Chemical Processes

Correction: Digestion does begin in the mouth, not the stomach.

Oral Digestion

• Mechanical: Mastication (chewing) increases surface area.
• Chemical: Salivary amylase (ptyalin) initiates starch → maltose digestion. Lingual lipase starts fat digestion (especially important in infants).
• Lubrication/Bolus Formation: Mucin in saliva binds food for safe swallowing.
• Antimicrobial: Lysozyme, IgA, peroxidase protect mucosa.

No Organelles Involved

Digestion is extracellular, mediated by secreted enzymes. Organelles (mitochondria, ribosomes, etc.) are intracellular structures—not involved in luminal digestion.

Stomach Role

Gastric amylase is inactivated by acid; pepsin begins protein digestion. The mouth's work is essential for efficient downstream digestion.