Food’s journey through the . . . DIGESTIVE SYSTEM

Digestion Digestion breaks food molecules down into smaller molecules It is necessary to make smaller molecules because these nutrients need to be used by CELLS. Only small molecules can pass through the cell membrane and into the cell so it can be used. EX: We break starch ( a large molecules) down into glucose (a small molecule that can cross cell membranes) so our cells can do respiration and make energy!

What are each of the following broken down into??? Digestion What are each of the following broken down into??? Proteins → Starch → Lipids → Carbohydrates → Steps of Digestion: Ingestion → Digestions → Absorption → Excretion Amino Acids Glucose Fatty Acids Simple Sugars

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 an enzyme (amylase) 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 What diseases or problems do you think of when you think of the digestive system? Diarrhea Constipation Appendicitis GERD IBS Ulcers Cirrhosis 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

http://nature.ca/discover/exm/blddgstvsystm/index_e.cfm http://kitses.com/animation/swfs/digestion.swf