The Digestive System

Nutrients Nutrients: substances in food that supply energy and raw materials for growth, repair, and maintenance Nutrients needed by body are: water, carbohydrates, fats, proteins, vitamins, and minerals

Water Most important nutrient many body processes & chem rxns take place in water Composes most body fluids

Carbohydrates main energy source Sugars broken down by digestive system and placed in blood stream Sugars are stored in tissue to create ATP

Fats Mainly used for cell membranes Insulation and protection Also used for hormones and myelin sheaths

Proteins Raw materials for growth and repair structures Skin and muscle Hormones and enzymes Insulin hemoglobin

Vitamins Vitamins: organic molecules that regulate body processes Work with enzymes From our food; We cannot make them (except vitamin D)

Minerals Minerals: inorganic nutrients needed in small amounts Calcium: bones Iron: hemoglobin

Gastrointestinal tract: long, winding tube which begins with the mouth and ends with the anus Digestion: process of breaking down food into molecules the body can use

Mechanical Digestion Teeth tear food into smaller pieces Tongue and palate form a small ball of food called a bolus Esophagus moves food to stomach by a series of wavelike contractions called peristalsis Stomach mixes and churns the food

Chemical Digestion Salivary amylase in saliva starts to break down starch into smaller sugars (glucose) Pepsin in stomach starts to break down proteins- * Reason why diabetics have to inject insulin. If taken by mouth the peptide hormone insulin will be broken down into smaller subunits of proteins called amino acids.

Esophagus 10 inch tube that connects the pharynx with stomach Located between trachea and spine Peristalsis moves food from pharynx to stomach Mucus is secreted in lining to moisten and aid in movement of food

Stomach Located between the esophagus and the small intestines sphincters at each end control movement of material in and out Contains pepsin Contains HCL(hydrochloric acid); acidic environment aids digestion Lining secretes mucus to protect stomach wall against being burned by HCL

Ulcer

Liver- Accessory Organ of Digestive System Produces bile - emulsifies fat to help digestion by enzymes Also filter blood of harmful and toxic substances like alcohol, and drugs

Gall Bladder-Accessory Organ Stores bile After eating a meal the gall bladder will contract and squirt bile into small intestine.

Pancreas – accessory organ Helps neutralize stomach acid Pancreatic enzymes digest carbs, lipids, proteins, and nucleic acids

Small Intestines Located between the stomach and the large intestines About 23 ft. long About 1 inch in diameter Site of absorption of nutrients Contain villi and microvilli-fingerlike extensions that increase surface area Chemical digestion of lipids, proteins and carbohydrates Receives bile from gall bladder/liver, and enzymes from the pancreas

Villi (Villus sing.)

Large Intestines absorption of water from undigested material occurs Bacteria present which aid in production of vitamin K Taking antibiotics can cause a vitamin K deficiency

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Appendix www.kucau.net/.../uploads/2007/10/appendix.jpg