Digestive System

Purpose To breakdown food To absorb nutrients To remove waste (un-usable food products) General Terms – Lumeninternal cavity – Chymefood material + digestive secretions

Nutrition What do we need to be healthy? Of all the vitamins and minerals needed in the human diet, do you know which food (specific) contains more than any other? Vitamin B (water soluble) play roles as coenzymes (help enzymes) Vitamin A, D, E, K (fat soluble) play many roles: – Vitamin A plays a role in vision (retinol) – Vitamin D allows calcium absorption – Vitamin E is less understood Vitamin C plays a role in creating collagen, a protein used in bone, muscle, skin, cartilage, tendons, etc.

Mouth/Esophagus Use of Physical and Chemical means to begin digestion Physical digestion is performed by the teeth and jaw. Food is broken down into smaller components. Chemical digestion begins with saliva. Saliva contains some enzymes involved with the breakdown of starch (amylase) Food moves down the esophagus to the stomach, the barrier that separates the two is called the esophageal sphincter. How do you get heartburn? Or acid reflux disease?

Stomach Food is stored in the stomach up to 4 hours Stomach is used to breakdown food materials physically. (physical change) Caffeine, alcohol, and asprin are absorbed in small amounts in the stomach HCL is secreted in the stomach to keep the pH between 1 and 3. This does a couple of things – Allows the enzyme pepsinogen to become active (pepsin) which is the main digestive enzyme – Kills microbes that were taken in with the food – High acidity causes bonds to break which helps in digestion

Small Intestine Major site of digestion and absorption. Over 6 meters (20 feet) long, separated into 3 sections – Duodenum (most of the digestion takes place) – Jejunum (with the Ileum, 90% of absorption takes place) – Ileum (absorption takes place through mirco- villi) pH changes from acidic to basic (pH 10-12) Food (chyme) is pushed slowly, a little at a time into the small intestine allowing the intestine to work on bits at a time.

Absorption Along the inside wall of the small and large intestine are projections called micro-villi (primary absorption sites) This increases surface area and slows the progress of food through the system High blood supply allows absorbed nutrients to diffuse into the blood stream to be carried to the rest of the body

Enzymes / Digestion Factors Several organs play a role in producing enzymes for digestion – Liver/ Gall Bladder produces and stores bile for fat breakdown and absorption (bile duct) – Pancreas produces 6 – 8 different enzymes that help digestion of all food types – Small intestine also produces 7 different enzymes that affect digestion

Large Intestine Primarily responsible for the absorption of water and ions Contains millions of bacteria, one of the most commonly known and studied is E-coli Mutualistic relationship exists, bacteria receive food humans are unable to digest, in return we get many different vitamins from the bacteria as they digest the food.