Digestion

Digestion

Lifetime Nutrition and Wellness

TEKS: 2ABC

http://kidshealth.org/kid/htbw/_bfs_DSmoviesource.html

Digestion

• Before your body can use the nutrients in the food you eat, it must go through digestion.
• Then nutrients must go through absorption.
• Digestion-the bodily process of breaking food down into simpler compounds the body can use
• Absorption-the process of taking in nutrients and making them part of the body

The Digestive Tract

• The digestive or gastrointestinal tract is a tube about 30 feet long.
• It extends from the mouth to the anus.
• Contains the esophagus, stomach, small intestine, and large intestine
• They work together to both mechanically and chemically help the body use food.

The Digestion Process

• The body breaks down complex molecules from the food into simple, soluble materials.
• They pass through the digestive tract into the blood and lymph systems.
• Vitamins and minerals undergo very little chemical change during digestion.
• Fats, proteins, and carbs undergo many changes.

The Mechanical Phase

• Begins in the mouth, the teeth chew the food and break it down into small pieces
• Contractions of the muscular walls of the digestive tract carry on the mechanical action. The contractions mix food particles and break them into smaller pieces
• Waves of contractions knows as peristalsis, the muscles push food through the digestive tract
• Emotions can slow down or speed up the process

The Chemical Phase

• Begins in the mouth
• As you chew, food is mixed with saliva. (mucus and enzyme containing liquid)
• It moistens food particles, helping them move down the esophagus into the stomach.
• Saliva also begins to break down starches.

The Chemical Phase

• In the stomach, gastric juices containing hydrochloric acid and several enzymes are secreted.
• These juices break down the food more.
• Ordinary meal usually leaves the stomach in about 2 to 3 hours
• Carbs leave the stomach first, proteins second, fats last
• You will feel hungry sooner after a meal high in carbs

Chemical continued…

• Then the semi-liquid food leaves the stomach and enters the small intestine
• Intestinal juices, pancreatic juices, and bile act on the food
• Digestive enzymes help break down the carbs, proteins, and fats into simple substances the body can absorb and use.
• Once digestion is complete absorption can take place.

Large Intestines

• Indigestible residues, bile pigments, other wastes, and water travel from the small intestine to the large intestine.
• The large intestine acts as a reservoir, or storage area.
• Eventually the body will excrete these materials.

Absorption Process

• The body can absorb water, ethyl alcohol and simple sugars directly from the stomach.
• They pass through the stomach walls into the bloodstream.
• However, most absorption takes place in the small intestines.

Absorption Process

• Millions of hair like fingers called villi line the small intestines.
• The villi increase the absorptive surface of the small intestine by more than 600%.
• Each villus contains a lymph vessel surrounded by a network of capillaries.
• Nutrients absorbed by the capillaries pass into the portal vein and travel directly to the liver.

Metabolism

• The chemical processes that take place in the cells after the body absorbs nutrients
• Enzymes cause nearly all metabolic reactions.
• The body uses nutrients to replace substances used for growth and to carry out body processes.

Metabolism

• The body breaks down some nutrients into simpler substances to release energy.
• The body uses part of this energy to carry out metabolic reactions.
• It converts the rest into heat.
• The body converts all carbs into glucose for use as an energy source.
• If they are not needed for immediate energy, they can be converted to glycogen or in the body as fat tissue.

Metabolism

• During fat metabolism, fatty acid chains are shortened. The body uses most fat for fuel.
• The body can use amino acids from protein metabolism for cell maintenance or cell growth.
• It can also use amino acids to make enzymes, antibodies, nonessential amino acids, and as an energy source.

• http://kidshealth.org/parent/general/body_basics/digestive.html
• http://www.neok12.com/php/watch.php?v=zX43417c4d68676e7352667b&t=Digestive-System