Human Digestion and Nutrition
Introduction to Digestion
Your Body's Fuel Factory
Everything you eat and drink is processed by your digestive system. Its main job is to break down food into smaller molecules that your body can absorb and use. These molecules provide the energy for every jump, thought, and breath. They're also the building blocks for growth and cell repair.
Think of the digestive system as a long, winding tube that runs through your body. This tube is called the gastrointestinal (GI) tract or digestive tract. Food enters one end and makes a journey through several key organs before waste exits the other.
The digestive system is a very long tube threw which food travels and is made up of the following parts: the mouth (which is where the digestion begins), the pharynx (which also belongs to the respiratory system), the esophagus, the stomach, the small intestine and the large intestine.
The path is always the same. Food starts in the mouth, travels down the esophagus to the stomach, then moves through the small intestine and finally the large intestine.
The Helper Organs
Not all digestive organs are part of the main tube. Several accessory organs play crucial supporting roles. The pancreas, liver, and gallbladder produce and store special chemicals, like enzymes and bile, that are essential for breaking down food. They deliver these substances into the small intestine at just the right moment.
Digestion and Absorption
The entire process relies on two key actions: digestion and absorption. First, food must be broken down. This happens in two ways. Mechanical digestion involves physically breaking food into smaller pieces, like when you chew. Chemical digestion uses enzymes to break down food molecules into their basic components.
Once food is broken down, the body can absorb the nutrients. This is the process of pulling the useful bits—vitamins, minerals, proteins, fats, and carbohydrates—out of the intestine and into your bloodstream, where they can be transported to cells all over your body.
Let's review the key players in this system.
Now, test your understanding of the digestive system's basic functions and components.
What is the primary function of the digestive system?
Chewing food in the mouth is an example of __________ digestion.
Together, these organs and processes work in a coordinated effort to fuel your body. In the next sections, we'll take a closer look at each part of this incredible system and see exactly how it contributes.