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Food
All creatures – from single cell organisms to the very complex multi-celled organisms such as animals and humans – have two processes that are basic and common to all. They all must ingest food (nutrients that create energy) and excrete waste (unusable by-products of metabolism). This lesson will focus on the process of ingesting food.
Types of Nutrients
As you learned earlier, major nutrients break down into two categories: macronutrients and micronutrients.
Macronutrients are:
- carbohydrates
- fats
- proteins
Macronutrients are sources of energy and provide calories that are burned for energy. This energy is not just the kind that makes you run fast on the football field; it also makes your brain function well, builds cells and body organs, and keeps you from running out of steam before the day is through.
Macronutrients break down into smaller components during the digestive process. These smaller parts are called micronutrients.
Micronutrients include:
- vitamins
- minerals
Micronutrients are not sources of energy and they do not contains calories.
Vitamins and minerals must be provided to the body from the food we eat or by taking nutritional supplements.
While vitamins and minerals do not contain calories themselves, they act as important co-factors or co-enzymes to assist in the release of energy from the macronutrients.
They play hundreds of roles all through your body. Some of their functions are to heal wounds, strengthen bones, fight infections, convert food into energy, and build and repair cells.
Both the macronutrients and the micronutrients are essential, meaning they are needed by the body but cannot be made by the body. There are some nutrients that the body can make on its own, but essential nutrients must come from food or supplements.
Water
Not a macro- or a micro-nutrient, water is the most important of all nutrients. It does not create energy and does not contain any calories.
Water helps to regulate your body temperature, lubricate joints and organs, carry nutrients to cells, and move waste products out of cells.
Did you know...? You can live up to 21 days without food but will probably only last about 3 days without water. And, the human body is 58% water.
Digestion
Digestion is the conversion of food in the mouth, stomach and intestines into soluble and diffusible material capable of being absorbed by the blood.
Put in plain words, digestion is the process of masticating (chewing) food, swallowing it, and breaking it down into smaller particles in the stomach and small intestines.
Once the digestive process has delivered the broken-down smaller particles to the small intestines, absorption can take place. Absorption is the process by which the building block materials of growth and nutrition are absorbed and conveyed to the tissues and organs.
Absorption occurs through the intestinal wall into the blood stream, allowing nutrients get from the food into the blood stream and then into the cells.
The purpose of digestion is to assimilate (or absorb) nutrients in the body. Digestion breaks down the food into usable components that send energy to the cells.
Parts of the Digestive System
There are many parts to the digestive system and each part has its own function. All are necessary to break food down into usable elements for the body and the cells.
In the next lesson, you will learn the specific path food takes through the digestive system and the functions of each part.