To :Mr.Gunderpants From: Kelsey Lalonde 8B Science January 2009

By: Kelsey L. Sarah K. Marvin T. Kyle F. Amber C. The Digestive System By: Kelsey L. Sarah K. Marvin T. Kyle F. Amber C.

Structures and Functions Salivary-Glands Mouth Esophagus Stomach Liver Pancreas Gall Bladder Small/ Large intestine Functions: Breaks down food into much smaller pieces so they can be absorbed and transported throughout the body

Types of Digestive Mechanical: Involves an actual physical breakdown of FOOD into very small pieces Chemical: Breaks down larger PARTICLES into small particles by substances called ENZYMES

The Mouth and Esophagus The First Steps of Digestion! Teeth mechanically digestive your food Saliva is produced from Salivary Glands (they are located in tissues surrounding the mouth) Saliva chemically digests your food - Saliva has water in it to moisten the food - Saliva also has enzyme which breaks down molecules (figure 3.3) The tongue moves the food to the back of your throat A flap of skin called the epiglottis moves across the windpipe to let food in Then your muscles in your esophagus contract so food can go down (figure 3.4)

The Stomach Your food has now made it to the stomach! Now what? The stomach has a couple jobs to do The walls of the stomach which are very muscular churn the food back and forth The walls of the stomach also releases Gastric Juice which chemically digests food as well - Gastric Juice contains mucus, hydrochloric acid, water, and digestive enzymes (figure 3.6) Now the food is on its way to the small intestine!

The Small intestine, pancreas, Liver, and Gall Bladder These are the jobs for the lower part of the digestive system The pancreas sends digestive enzymes into the small intestine The breakdown of starches and protein into very small particles is complete due to the enzymes that the pancreas sent and the enzymes already in the small intestine The liver produces bile (a liquid that helps digestion), which is stored in the gall bladder, then is sent to the small intestine The small intestine absorbs the particles

In Addition to the Small Intestine… Once absorbed the particles, the small intestine forms in villi- small, finger like projections (figure 3.9) VILLI… These increase when absorbing nutrients Each is covered with epithelial tissue There are blood vessels below the tissue so the nutrients can be absorbed into the blood stream MICROVILLI The epithelial tissues have villi as well because the tissue has modified cell membranes

These are the last steps!!!! The Large Intestine These are the last steps!!!! By this time, both types of digestion are complete! The large intestine absorbs water, vitamins, and minerals Any part of the food that has not been digested are formed into feces and is collected in the rectum

PICTURES!!!! Villi Stomach Peristalsis in esophagus

Fun Facts The Small intestine takes about six hours to complete digestion! Food takes 10 seconds to travel down the esophagus from throat to stomach Enzymes increase by thousands or millions of times! The alimentary canal is about 29 feet (9 m) from mouth to anus There is 4 lbs of friendly bacteria living in your colon The stomach can increase from 50 ml to 4 LITERS!!!!!!!! Liver cells are masters at multitasking! The perform more that 500 vital functions like making bile, process, store, and dispatch nutrients and rid the blood of poisonous chemicals All these facts from the book Dr. Frankenstein's Human Body Book