Digestive System

Functions 1. Breaks down the food so that the body can use it 2. Molecules are absorbed in the blood and carried throughout the body 3. Solid wastes are eliminated from the body

An overview of the process

Digestive Process Begins

4 Processes of Digestion Ingestion: Getting food into our bodies Digestion: Breaking down food into smaller nutrients Absorption: Getting those nutrients into our bloodstream, so that our cells can use them Elimination: Getting rid of solid waste products Eat it! Break it Down! Soak It Up! Go to the Bathroom!

2 Types of Digestion Digestion means breaking down food into smaller particles, called nutrients There are 2 kinds of digestion Mechanical: Food is broken down by physical processes (chewing, grinding, moving etc.) AND Chemical: Food is broken down by chemicals (saliva and acids)

What are nutrients? Nutrients are things that our bodies need to survive: Water = H2O Proteins Carbohydrates Fats Vitamins Minerals

Mouth Functions: Mechanically breaks down food by chewing Wets the food with saliva Chemically breaks down food with enzymes in saliva

Saliva Saliva-fluid that is released to help break down food chemical digestion- enzymes in saliva mechanical digestion- soften the bolus for easier swallowing

Teeth Digestion starts here. The job of the teeth is to start tearing and crushing the food down into small enough pieces so that it can fit down our throats.

Epiglottis Epiglottis- A flap called the epiglottis closes over the top of the trachea (windpipe) when swallowing, so that food does not enter the respiratory tract Mucus helps food go down easier

Esophagus Functions: Involuntary smooth muscles contract and push food toward the stomach

Peristalsis The walls of the digestive tract from the esophagus to the anus are muscular, and contract rhythmically to move food. The muscular contractions are called peristalsis

Stomach Functions: The lining releases digestive juice, which contains: Pepsin- Enzyme that breaks down protein Hydrochloric Acid (HCl) - Strong Acid to kill any bacteria you may have ingested Thick stomach muscles create a churning motion to mechanically digest food What type of internal stimulus causes vomiting?

What’s that sound? Stomach growling occurs when the stomach receives signals from your brain to begin digestion but the stomach is empty. Your brain might sense you're running low on energy or even seeing or smelling something you want to eat can get things going. The motion of the stomach muscles begins, but the organ is hollow. The movement of the muscles mixing the acids of the stomach in the hollow space of the stomach produces vibrations we hear as growling, or rumbling, or gurgling. Picture from: http://www.cartoonstock.com/newscartoons/cartoonists/awh/lowres/awhn31l.jpg * Dogs eat grass when they feel nauseated. They want to throw up, because they have learned that they feel better afterwards. *See slide note

Pancreas Attached near the first part of the small intestine Produces enzymes that help breaks down starches, fat and proteins that goes into the small intestines Does not break down fiber

Liver and Gallbladder LIVER: Breaks down medicines, other substances and helps break down nitrogen Produces Bile- breaks up fat particles into small droplets Gallbladder-stores the bile After you eat the bile passes through a tube from the gallbladder into the small intestine.

Small Intestine Functions: Peristalsis (contraction and relaxation of muscles) to push the food through Chemical Digestion through enzymes Absorption of nutrients to the blood

Blood Functions: Blood Vessels are found within the villi of the small intestine, here they absorb nutrients and deliver to the entire body

Drying Out and Exiting the Body By the time the food that was eaten leaves the small intestine, most of the usable nutrients have been digested and absorbed. The remaining undigested material moves into the large intestine where large amounts of water are removed and the final undigested wastes exit the body through the rectum (stored waste material) and anus (comes out). The large intestines also contain large amounts of bacteria (some sources say over 700 types!) that digest some of the remaining material and produce certain vitamins. These bacteria also produce GAS as a by product! Rectum Anus Large Intestine Appendix Picture of girl from: http://superweeds.com/images/e_3half_surprised.jpg Digestive system images from Servier Medical Art: http://www.servier.com/smart/imagebank.aspx?id=729 So that’s where it comes from!

Fun Digestive Facts: On average, the stomach produces 2 -2.5 liters of Hydrochloric Acid daily. After you eat, it takes usually between 24 and 72 hours in healthy adults for the complete process of digestion to occur. In the mouth, food is either cooled or warmed to a more suitable temperature. Food stays in your stomach for 2 to 3 hours. The average male will eat about 50 tons of food during his lifetime in order to sustain a weight of 150 pounds. http://health.howstuffworks.com/diseases-conditions/digestive/healthy-digestion2.htm

More Fun Digestive Facts The liver is the largest and heaviest internal organ of the body and weighs about 1.6 kilos. The Liver is the only organ of the body, which has the capacity to regenerate itself completely even after being removed almost completely. Scientists estimate that the average adult releases between 12 and 122 cubic inches of intestinal gas each day. Most of that gas is made up of hydrogen and methane produced by the bacteria as they ferment the fiber that was not digested in the stomach or small intestine.