Digestive_system_I_F2020

Digestive System Overview

Energy Acquisition: We consume food to obtain energy essential for survival.
Raw Material: Food provides raw materials required to build body tissues.

Both the human body and food are composed of "stuff" that contains energy stored in atomic bonds.

Converts chemical energy in food (carbohydrates, proteins, fats) into usable energy for cells and tissues, allowing them to perform essential functions.

Unhealthy Foods: Fast foods are high in calories but low in essential nutrients (e.g., hamburger, fries, soda).
Healthy Foods: Well-balanced meals meet the body's nutritional needs (e.g., nutritional shake with milk and fruits).

Calories: A measure of energy stored in food.
Macronutrient Breakdown:
- Carbohydrates: approx. 4 calories per gram.
- Fats: approx. 9 calories per gram.
- Proteins: essential for bodily functions.

Ingestion: Intake of food through the mouth.
Propulsion: Moving food through the digestive tract (includes voluntary swallowing and involuntary peristalsis).
Mechanical Breakdown: Physical processes (e.g., chewing) that break down food into smaller pieces.
Chemical Digestion: Enzymatic breakdown of food into smaller molecules.
Absorption: Nutrients are absorbed in the small intestine and transported to cells.
Excretion: Elimination of indigestible substances from the body.

Enzymes are proteins that speed up chemical reactions necessary for digestion.
They break down macromolecules into absorbable monomers (lipids, carbohydrates, proteins, nucleic acids).

Macromolecules (Polymers): Complex substances that need to be broken down for absorption.
Monomers: The smaller units (e.g., fatty acids, sugars, amino acids) that can be directly absorbed and utilized by the body.

Digestive Tract: A muscular tube extending from the mouth to the anus, including structures such as the esophagus, stomach, small intestine, and large intestine.
Accessory Organs: Include teeth, tongue, salivary glands, liver, pancreas, and gallbladder that aid in digestion.

Stratified Squamous Epithelium: Protects against abrasions, especially in the mouth and esophagus.
Simple Columnar Epithelium: Important for secretion and absorption in the intestines.
- Contains goblet cells for mucus secretion, providing protection and facilitating movement.

Ingestion: Introduction of food into the digestive system through mechanical and chemical means.
Propulsion: Movement through the digestive tract facilitated by peristalsis.
Mechanical Breakdown: Teeth grinding and churning in the stomach.
Chemical Digestion: Cytolytic enzymes reduce food to basic nutrients (amino acids, glucose, fatty acids).
Absorption: Nutrient transfer from the small intestine into the bloodstream.
Excretion: Disposal of indigestible remains from the body.