Food’s journey through the...

Types of Digestion  Mechanical – physically breaking food down into smaller pieces  This creates more surface area, so enzymes can get to more molecules  Chemical – use of chemicals and enzymes to break food into substances that can be absorbed

Mouth  Teeth are used for mechanical digestion to break the food into smaller pieces, so it can be easily swallowed.  Saliva contains enzymes used in chemical digestion, which breaks down starches into simple sugars  The tongue is your strongest muscle used to manipulate food during mastication

Esophagus  The tube the food travels down to get to the stomach  Peristalsis is the motion that pushes the food down the tube. The tube pinches off above the food pushing it toward the stomach  You have an epiglottis that covers your esophagus while you are breathing and covers your trachea while you are swallowing  This prevents food from “going down the wrong tube”

Stomach  The stomach performs mechanical and chemical digestion of food.  The stomach secretes a powerful acid (pepsin) that breaks food down  It also churns mixing the food with the acid and breaking it down mechanically  Chyme is the mixture of stomach acid (pepsin), broken down food, and saliva that flows from the stomach into the small intestine

Duodenum  This is the first section of the small instestine, where most of the chemical digestion of carbohydrates, lipids, and proteins occurs  Chyme is joined with enzymes from the liver and pancreas that reduce acidity of the chyme and chemically digest the food

Small Intestine  The small intestine are covered in little finger like projections called villi  Villi increase the surface area of the small intestine to increase absorption of nutrients  The usable nutrients are removed from the chyme and travel across the villi into the blood vessels that are inside it

Large Intestine  When the food arrives in the large intestine it is nutrient free  The large intestine pulls any excess water out of the remaining indigestible material creating feces  The large intestine is filled with bacteria that help our digestion process  When the large intestine is not removing enough water, diarrhea will result  When the large intestine removes too much water, constipation will occur

Rectum  The rectum will store the feces until there is enough to pass out of the body  When the rectum is full, you feel the urge to go to the bathroom  There is a sphincter muscle at the bottom of the rectum called the anus  This squeezes shut to keep feces in the rectum and expands to allow it out when passing a stool

Liver, Pancreas, & Gallbladder  The liver and pancreas secrete enzymes and digestive fluids that mix with the chyme in the duodenum  The pancreas secretes a fluid to neutralize the acidity of the stomach acid  The liver secretes bile, which is used to break down fatty acids (lipids)  Bile is stored in the gallbladder

Appendix  Is located near the junction of the small and large intestine  The appendix is a vestigial organ, which means it was once used but shrunk in size as it became less useful  Some organisms use the appendix to help break down cellulose in very fibrous substances (leaves)

Common Diseases  Diarrhea  Constipation  Appendicitis  GERD  IBS  Ulcers  Cirrhosis What diseases or problems do you think of when you think of the digestive system?  Diverticulitis  Ulcerative Colitis  Hemorrhoids  Celiac’s  Lactose Intolerance  Stomach Ache

Diarrhea and Constipation  Diarrhea – too much fluid in the bowel movements  Caused by the large intestine not removing enough water  Can be caused by viruses, bacteria, etc.  Can lead to dehydration and eventually death  Constipation – too much water being removed from the bowel movements  Can be caused by poor diet or not taking in enough water  Symptoms can be alleviated by taking laxatives

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