Human Digestion Overview

Human Digestion

The human digestive system is responsible for breaking down food into smaller molecules that can be absorbed and utilized by the body. This process involves various organs working together to ensure proper nutrient absorption.

Stages of Human Digestion

Oral Processing

The process begins in the mouth, where teeth grind food with salivary enzymes starting the initial break down. Saliva also moistens the food, facilitating its passage to the stomach.

Gastric Processing

In the stomach, the mixture of food and digestive juices forms chyme, which is then passed into the small intestine. Gastric juices contain hydrochloric acid and enzymes.

Small Intestinal Processing

Enzymes from the pancreas and bile from the liver break down complex nutrients in the small intestine. Here, most nutrient absorption occurs through the walls of the small intestine.

Colon and Rectum

Unabsorbed food residues pass into the colon for further processing by bacteria, producing methane and carbon dioxide. Eventually, waste products are eliminated through the rectum and anus.

Types of Nutrients and Their Breakdown

Proteins

Proteins are broken down into individual amino acids in the stomach and small intestine. These acids are then absorbed and used for protein synthesis elsewhere in the body.

Carbohydrates

Carbohydrates are primarily broken down into glucose in the small intestine, which is then absorbed into the bloodstream for transportation throughout the body. Excess glucose is stored as glycogen in the liver, and unneeded glucose is converted into fat for later use.

Fats

Fats are broken down into fatty acids and glycerol in the small intestine. These molecules are absorbed and transported via the bloodstream to cells that require them for energy production or storage. Unused fatty acids can also be stored in adipose tissue for future energy needs.