The Digestive System

General Structure & Function Series of connected hollow organs and accessory organs Food molecules are broken down and absorbed to be used by cells for energy Main Organs Accessory Organs Mouth Liver Esophagus Gall Bladder Stomach Pancreas Small Intestine Large Intestine

The Digestive System

How is food digested? Digestion involves: Mechanical (Does not change substance) Chewing/grinding/mixing of food into smaller pieces Movement through the digestive tract (Peristalsis) and out into the blood (Diffusion) Chemical (Changes substance into something brand new) breakdown of the large molecules of food into smaller molecules by enzymes

What is absorption? Transfer of nutrients from the digestive system into the circulatory systems (diffusion) for eventual use by cells. Most absorption takes place in small intestine Except for water, sodium and end products of bacterial digestion which are absorbed in the large intestine

What are Enzymes? Chemicals that break down specific large food molecules into smaller, usable molecules

Main Organs

Mouth Opening in which animals take in food. In humans the mouth includes teeth, tongue, salivary glands, and saliva. Mechanical Digestion: Teeth bite off and chew food into a soft pulp and moisten with saliva so that is easy to swallow. Chemical Digestion: Enzymes in the saliva begin digestion of carbohydrates.

Esophagus The esophagus is a muscular tube. It takes food from the throat and pushes it down through the neck, and into the stomach. It moves food with mucus and waves of smooth muscle contraction called peristalsis.

Video: https://www.youtube.com/watch?v=OzLoUCCASwM Stomach The stomach is a J-shaped organ that is composed of smooth muscle walls and specialized cells that create strong digestive juices. Mechanical Digestion: Thick muscular walls contract to mash the food into a watery soup called chyme. Chemical Digestion: Stomach lining produces strong digestive juices (Hydrochloric Acid) which cause chemical reactions, breaking down food into simpler parts and dissolving its nutrients. Pepsin: Helps digest proteins into amino acids Video: https://www.youtube.com/watch?v=OzLoUCCASwM

Small Intestine Long (6 meters) tube-like structure responsible for further breakdown of food particles into nutrients the body can absorb through diffusion. Mechanical Digestion: Diffusion of nutrients out through the linings in the villi into capillaries. Chemical Digestion: Enzymes continue the chemical reactions on the food. Video: https://www.youtube.com/watch?v=UgnF1w-H8vw

Video: https://www.youtube.com/watch?v=Lzr9GGjh6YQ Large Intestine Large tube-like structure (1.5 meters) responsible for the final stages of digestion (Contain Rectum and Anus). Mechanical Digestion: Diffusion of useful substances that were not absorbed in the small intestine (water and body minerals). Chemical Digestion: Bacteria in the large intestine process any remaining nutrients releasing minerals. Video: https://www.youtube.com/watch?v=Lzr9GGjh6YQ

Accessory Organs

Video: https://www.youtube.com/watch?v=rDjWrNRKfvg Liver The largest gland of the body. The liver is reddish-brown and primarily rests on the top right of the abdomen. Mechanical Digestion: Produces bile to be secreted into the small intestine to break up fat particles. Chemical Digestion: Blood from the intestines enters to the liver, carrying nutrients, vitamins and minerals, and other products from digestion. The liver stores some nutrients, changes them from one form to another, and releases them into the blood according to the activities and needs of the body. Video: https://www.youtube.com/watch?v=rDjWrNRKfvg

Video: https://www.youtube.com/watch?v=jmfcACEGW-0 Gall Bladder A small bag-like sac under the liver which stores bile made in the liver. Mechanical Digestion: Secretes bile through a tube connected to the small intestine which breaks up fat particles into smaller and smaller pieces. Video: https://www.youtube.com/watch?v=jmfcACEGW-0

Video: https://www.youtube.com/watch?v=BtqlMr1rUT8 Pancreas The pancreas is a triangular shaped organ that lies between the stomach and the first part of the small intestine. Chemical Digestion: Like the stomach, the pancreas makes digestive juices called enzymes which help to digest food further as it enters the small intestines. Video: https://www.youtube.com/watch?v=BtqlMr1rUT8

Describe water Most nutrients in your body can't be used unless they are carried in a solution. This means that they have to be dissolved in water. In cells, chemical reactions take place in solutions. Most of the material absorbed from the cavity of the large intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.

Helpful Websites Animation Site Review Site Digestive Overview http:/www.kitses.com/animation/swfs/digestion.swf Review Site http:/www.anatomyarcade.com/games/jigsaws/DigestiveJigsaw/digestiveJigsaw.html Digestive Overview http://kidshealth.org/kid/body/digest_noSW.html