Question

1. Explain how mechanical digestion enhances chemical digestion.

2. Explain how the structure of the small intestine enhances its function.

Answer 1

Answer

1)

• Mechanical digestion refers to breaking large food particles ingested through mouth into smaller pieces.
• Major structures involved in mechanical digestion are : Tongue, teeth and smooth muscles of esophagus, stomach.
• In mouth, tongue and teeth helps in grinding of food into small pieces. Saliva moistens the food and forms bolus.
• In esophagus, peristaltic waves breaks down the food further and transport oit to the stomach. Antrum region of stomach perform churning of food to further reduce its size.
• Mechanical digestion helps to increase contact between digestive enzymes and the food.
• Emulsfication of lipids in small intestine by bile also breaks large molecules into small fat droplets. Chemical lipase acts on these droplets to convert them into absorbable form.

2)

• The mucosa layer of small intestinal wall has unique structure.
• The cells of the mucosa layer (simple columnar epithelial cells), contains extensions from the plasma membrane called villi and microvilli.
• These finger-like projections increases the surface area for absorption of nutrients.
• There are numerous folds in the mucosal layer known as plicae circulares. These folds allows digested food to move slowly through the lumen and increase contact of nutrients to the absorptive cells.
• In this way, structure of the small intestine enhances its function