Overview
This lecture explains the processes of mechanical and chemical digestion in humans, detailing how food is broken down and nutrients are absorbed.
Introduction to Digestion
- Digestion transforms food into basic chemicals for absorption and use by the body.
- This process enables absorption of calories, nutrients, vitamins, and minerals essential for growth and repair.
Mechanical Digestion
- Ingestion begins when food enters the mouth.
- Teeth chew food, breaking it into smaller pieces (mechanical digestion).
- The stomach and intestines continue physical breakdown through muscular movements.
Chemical Digestion
- Chemical digestion uses enzymes and acids to break complex molecules into smaller ones.
- Saliva in the mouth contains amylase, which begins starch breakdown into maltose.
- The stomach uses enzymes and hydrochloric acid for further chemical digestion.
- Most chemical digestion occurs in the small intestine, starting in the duodenum.
- Pancreatic juice, an alkaline mixture, neutralizes stomach acid and digests lipids, carbohydrates, proteins, and nucleic acids.
- Small intestine enzymes further convert maltose into glucose.
Absorption and Waste Processing
- The small intestine’s villi absorb nutrients and minerals into the bloodstream.
- Each villus links to blood vessels for nutrient transport.
- The large intestine handles undigested food, which is expelled as waste via the rectum.
Key Terms & Definitions
- Digestion — process of breaking down food into absorbable chemicals.
- Mechanical Digestion — physical breakdown of food into smaller pieces.
- Chemical Digestion — enzymatic and chemical breakdown of food molecules.
- Amylase — enzyme in saliva that converts starch to maltose.
- Villi — finger-like projections in small intestine that absorb nutrients.
- Pancreatic Juice — alkaline fluid from pancreas that digests major food groups.
Action Items / Next Steps
- Review functions of key digestive enzymes.
- Study the structures and functions of each digestive organ.