By Diego Irizarry and Andrea Caro The Digestive System By Diego Irizarry and Andrea Caro

Functions Four steps: Ingestion: Food is ingested Digestion: the breakdown of food into small particles Absorption: Nutrients and water in the food are absorbed by cells Elimination: The removal of undigested food from your body.

Types of digestion Two types: Mechanical digestion: food is physically broken into smaller pieces. Happens when you chew, mash, and grind food with your teeth and tongue. Chemical digestion: chemical reaction break down pieces of food into small molecules. Enzymes: proteins that help break down larger molecules into smaller molecules. Enzymes speed up the rate of chemical reaction.

Role of Enzymes The digestive system produces enzymes to help break down each type of food molecule. The food molecule breaks apart, the enzyme does not change. The enzyme can immediately be used to break down another food molecule.

Organs of the digestive system Digestive trac, tongue, salivary glands, liver, gallbladder, and pancreas. The digestive trac extends from mouth to the anus.

Mouth The Esophagus Mechanical digestion of food begins in your mouth. Your teeth and tongue mechanically digest food as you chew. Your salivary glands produce saliva. Esophagus: Muscular tube that connects the mouth to the stomach. Peristalsis: Wave of muscle contractions As muscles in the esophagus contract and relax, partially digested food is pushed down the esophagus and into the stomach. The Esophagus

The stomach One function of the stomach is to temporarily store food. Another function of the stomach is to aid in chemical digestion. The stomach contains ad acid fluid called gastric juice. Acid helps break down some of the structures that hold plant and animal cells together.

The stomach

The small intestine Most chemical digestion occurs in the small intestine. The small intestine is a long tube connected to the stomach. It is where chemical digestion and nutrient absorption occur. The folds of the small intestine are covered with fingerlike projections called villi. The pancreas and the liver produce substances that enter the small intestine and help with chemical digestion.

Bacteria and Digestion The large intestine The large intestine has a larger diameter that the small intestine. It is much shorter than the small intestine. Most of the water in ingested foods and liquids is absorbed in the small intestine. Materials that pass through the large intestine are the waste product of digestion. Muscles in the rectum and anus control the release of the semisolid waste, called feces. Bacteria and Digestion Bacteria digest food and produce important vitamins and amino acids.

The Digestive System and Homeostasis The digestive system must be functioning properly for this absorption to occur. These nutrients are necessary for other body systems to maintain homeostasis.

video http://www.youtube.com/watch?v=Z7xKYNz9AS0

Activities http://www.purposegames.com/game/1918 http://nature.ca/discover/exm/blddgstvsystm/inde x_e.cfm http://kidshealth.org/kid/htbw/_bfs_DSquizsource .html http://www.neok12.com/quiz/DIGSYS01