THE DIGESTIVE SYSTEM

Digestion- the process by which the body breaks down food into smaller nutrient molecules to be used by the body as fuel.

The three main functions of the digestive system are:• Break down food into molecules the body can use• Those molecules are then absorbed into the

bloodstream and carried throughout the body.• Waste elimination from the body

• There are very specific roles the mouth, esophagus, and stomach play in digestion.

The Mouth-both mechanical and chemical digestion occur here to help break down food.

Vocabulary • Digestion -see the first slide• Absorption-The process by which nutrient molecules pass

through the walls of the digestive system into the blood stream.• Saliva-The fluid released when your mouth waters, it contains an

enzyme that breaks down starch.• Esophagus- A muscular tube that connects the mouth to the

stomach.• Peristalsis- Involuntary waves of muscle contractions that keep

food moving through the digestive tract.• Enzyme-A protein that speeds up chemical reactions in the body.• Epiglottis-A flap of tissue that seals off the windpipe and

prevents food from entering.• Mucus-Slippery substance produced by the body, makes food

easier to swallow and move along.• Stomach- The J shaped muscular pouch located in the abdomen

• Mechanical digestion- process by which food is broken down physically.(ex. chewing, tearing, and grinding by the teeth)

• Chemical digestion- process of breaking food down by natural chemicals found in the body.

• Saliva, found in the mouth, contains an enzyme which chemically breaks down starch.

• The tongue helps mix the food with saliva and assist in swallowing.

The Esophagus

The muscular tube that connects the mouth to the stomach is the esophagus. As you swallow, a flap of tissue called the epiglottis seals off the windpipe , preventing food from entering. Mucus lines the esophagus and makes it easier to move along. Food is in esophagus for only about 10 seconds, after food enters the esophagus, contractions of smooth muscles pushes food toward the stomach; these contractions are called peristalsis.

The Stomach

• The j shaped pouch located in the abdomen is the stomach. Most Mechanical digestion and some chemical digestion occurs in the stomach.

• Mechanical digestion occurs as 3 strong layers of muscle contract to produce a churning motion.

• Chemical digestion occurs in the stomach by digestive juices that contain enzymes that break down proteins and hydrochloric acid that kills many bacteria that are swallowed with food.

• Food remains in the stomach until all the solid food is broken down into a liquid form usually after a few hours.

• The food now a thick liquid, is released into the next part of the digestive system for final chemical digestion and absorption.

Interactive Reader

http://www.learnerstv.com/animation/animation.php?ani=221&cat=biology

http://link.brightcove.com/services/player/bcpid1835313767001?bckey=AQ~~,AAAABNaOSDE~,

MV0hcnoQX_kTd8ed4mSztIztph6AcWZo&bclid=0&bctid=3637563797001