Digestive System Overview

Introduction

Eating serves two main purposes:
- To obtain energy for survival.
- To acquire raw materials for building tissues.
Humans and food are composed of matter and energy stored in atomic bonds.
Digestion converts food into usable forms at the cellular level.

Ingestion
- Introduction of food into the digestive system.
- Begins in the mouth.
Propulsion
- Movement of food through the digestive tract.
- Starts with swallowing and continues with peristalsis.
Mechanical Breakdown
- Physical smashing and grinding of food to increase surface area.
Chemical Digestion
- Enzymatic breakdown into monomers: amino acids, fatty acids, sugars.
Absorption
- Nutrients absorbed in the small intestine.
- Transported into the bloodstream.
Defecation
- Elimination of indigestible substances from the body.

Alimentary Canal (GI tract): Mouth to anus.
- Hollow organs: mouth, pharynx, esophagus, stomach, intestines.
- Tissue lining: stratified squamous and columnar epithelial cells.
Accessory Organs: Teeth, tongue, gallbladder, salivary glands, liver, pancreas.
- Secrete enzymes aiding in digestion.

Digestion involves mechanical and chemical processes.
Enzymes act as catalysts to break down macromolecules.
Macromolecules include lipids, carbohydrates, proteins, nucleic acids.
Digestion reduces these to monomers: fatty acids, sugars, amino acids, nucleotides.

Cells require monomers for energy and construction of new polymers.
The digestive process adapts to the body's changing needs for energy and materials.

Digestive system efficiently breaks down and processes food into energy and nutrients.
Provides the necessary components for cellular function and bodily maintenance.