Digestive System
Overview: Digestion is the process in which food is broken down and absorbed into the
bloodstream. This guide summarizes nutrients, the digestive tract, and the structure of the oral
cavity.
1. Classification of Nutrients
Organic substances
Carbohydrates – Primary energy sources (e.g., glucose, starch, cellulose).
Proteins – Building blocks of the body, made of 20 amino acids.
Lipids – Energy sources and components of cell membranes (fats, oils).
Inorganic substances
Important ions: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, HCO₃⁻
Water
2. Sections of the Digestive Tract
Section Parts Main Functions
Oral cavity, pharynx, Food intake, chewing, swallowing, initial chemical
Foregut
esophagus digestion
Stomach, small Main digestion and nutrient absorption; aided by liver
Midgut
intestine and pancreas
Water and mineral reabsorption, stool formation,
Hindgut Large intestine, rectum
cellulose breakdown by bacteria
3. Oral Cavity
The starting point of the digestive tract. Mechanical breakdown (chewing) happens here. Lined
with non-keratinized stratified squamous epithelium.
Dentition
Type of Dentition
Humans have heterodont dentition, meaning we have different types of teeth with different
shapes and functions.
Overview: Digestion is the process in which food is broken down and absorbed into the
bloodstream. This guide summarizes nutrients, the digestive tract, and the structure of the oral
cavity.
1. Classification of Nutrients
Organic substances
Carbohydrates – Primary energy sources (e.g., glucose, starch, cellulose).
Proteins – Building blocks of the body, made of 20 amino acids.
Lipids – Energy sources and components of cell membranes (fats, oils).
Inorganic substances
Important ions: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, HCO₃⁻
Water
2. Sections of the Digestive Tract
Section Parts Main Functions
Oral cavity, pharynx, Food intake, chewing, swallowing, initial chemical
Foregut
esophagus digestion
Stomach, small Main digestion and nutrient absorption; aided by liver
Midgut
intestine and pancreas
Water and mineral reabsorption, stool formation,
Hindgut Large intestine, rectum
cellulose breakdown by bacteria
3. Oral Cavity
The starting point of the digestive tract. Mechanical breakdown (chewing) happens here. Lined
with non-keratinized stratified squamous epithelium.
Dentition
Type of Dentition
Humans have heterodont dentition, meaning we have different types of teeth with different
shapes and functions.
