Which structure is the site of mechanical digestion and the start of carbohydrate digestion?

Which structure is the site of mechanical digestion and the start of carbohydrate digestion?

• A. Mouth
• B. Pharynx
• C. Esophagus
• D. Stomach

Answer: (A)

The mouth performs both mechanical and chemical beginnings of digestion. Chewing breaks food into smaller pieces, increasing surface area for enzymes to act. At the same time, saliva from the salivary glands contains salivary amylase (ptyalin), which begins breaking down starches into simpler sugars. This combination—physical breakdown by teeth and initial carbohydrate digestion by an enzyme in saliva—happens here. The pharynx and esophagus mainly move food along with little to no digestion, and the stomach churns the food and digests proteins, but its acidic environment inactivates amylase, so carbohydrate digestion doesn’t start there. Hence, the mouth is the site where both mechanical digestion and the start of carbohydrate digestion occur.

The mouth performs both mechanical and chemical beginnings of digestion. Chewing breaks food into smaller pieces, increasing surface area for enzymes to act. At the same time, saliva from the salivary glands contains salivary amylase (ptyalin), which begins breaking down starches into simpler sugars. This combination—physical breakdown by teeth and initial carbohydrate digestion by an enzyme in saliva—happens here. The pharynx and esophagus mainly move food along with little to no digestion, and the stomach churns the food and digests proteins, but its acidic environment inactivates amylase, so carbohydrate digestion doesn’t start there. Hence, the mouth is the site where both mechanical digestion and the start of carbohydrate digestion occur.