DIGESTIVE SYSTEM Function: Digestion, absorption and eliminate waste. Changing food so that they can be absorbed and used by cells.

Type of Digestion 1. Mechanical digestion Chewing, swallowing, peristalsis etc. break food into tiny particles, mix them well with the digestive juices and move them along the digestive tract. 2. Chemical digestion Breaks down large food molecules into smaller molecular by digestive enzymes.

Reference: assn.org/ama/pub/category/715 5.html

Digestion processes: Mouth (mechanical and chemical digestion – teeth and salivary gland) esophagus (mechanical peristalsis) stomach (chemical enzyme) small intestine (chemical enzyme) bile gallbladder liver pancreatic juice pancreas large intestine

Digestive juices and enzymes Enzyme digests Resulting products Saliva (accessory) Amylase (ptyalin)StarchMaltose Stomach (main) Gastric juice Pepsin (protease) Hydrochloric acid Lipase Protein Fat (not significant) Polypeptides Fatty acid Glycerol Liver and gallbladder (accessory) Bile Emulsified large fat droplets Small fat droplets Pancreatic juice (accessory) Protease (trypsin) Lipase Amylase Protein Bile emulsified fat Starch Amino acid (A.A.), peptide Fatty acid and glycerol Maltose Small intestine (main) Intestinal juice Peptidase Sucrase Lactase Maltase Peptide Sucrose Lactose Maltose Amino acid (A.A.) monosaccharide

Food Food is used as collections of nutrients in a form which is eaten, digested and metabolized to provide energy and materials that build and maintain the structure, regulate the function of the body. Major nutritional sources: 1. Organic compounds 1. Organic compounds – carbohydrates proteins lipids vitamins 2. Inorganic compound 2. Inorganic compound – water H 2 O 3. Minerals 3. Minerals: Na, K, P, S, Ca, Fe… etc.

Energy balance: 30~40% of energy are used for normal growth, development and activity. The rest is used for maintain body temperature. Food and Nutrition Board recommend: female: 2,000 Kcal male:2,700 Kcal 1Kcal: energy required to raise the temperature of 1 liter of H 2 O from 15~16°C Energy producing food: protein:4 Kcal/g carbohydrate4 Kcal/g fat9 Kcal/g

1. Organic Compounds A. Carbohydrate suggest intake: 50~100 g/day primary energy source eg. Sugar, starch B. Lipid 60~90 g/day fat containing compounds fat soluble vitamins: A, D, E, K  Vitamin A: vision, bone, teeth, anticancer  Vitamin D: control optimal blood level of Ca, P  Vitamin E: antioxidant agent  Vitamin K: blood clot Essential fat (lipid): linoleic acid

C. Proteins 40~60 g/day, but in USA about 100 g/day Essential amino acid: eg. Lysine, leucine, isoleucine and tryptophan Complete proteins from animal sources Incomplete proteins from plants eg. Peas and beans are good lysine source but low in trptophan; nuts, seeds and cereals are good source in tryptophan but low in lysine Complementary diet is important for vegetarians

Body Mass Index (BMI) Weight (lbs) x 704 =BMI (Height in inches) 2  BMI of 25 is ideal  Less than 25 is great  30 and above is very unhealthy