A. WHY DIGEST FOOD? • To make it smaller so it can pass through the small intestine wall and enter the blood. • To make it soluble so it can dissolve in the blood and be transported to cells. B. BALANCED DIET Provides enough nutrients and energy to sustain the body and ensure good health and growth Food Groups & Sources NUTRIENT ROLE CARBOHYDRATE Provides energy FAT An energy store Insulation PROTEIN Cell growth and repair VITAMIN C Maintains healthy gums, bones and teeth Helps heal wounds VITAMIN D Strong teeth and bones IRON Producing red blood cells FIBRE Pushing food through the gut WATER Chemical reactions occur within it • • • • • • • • • • MAIN SOURCES Pasta Rice Bread Potatoes Butter & margarine Cooking oils Crisps Chocolate Meat Dairy products • • • • • • Oranges Lemons Limes Broccoli & spinach Oily fish Milk and cereals • • • • • • Red meat Eggs Green vegetables Cereals Nuts Brown rice Deficiency Diseases CAUSES EFFECTS (a) Vitamin D TIREDNESS LACK OF SUNLIGHT DEPRESSION LACK OF OILY FISH IN DIET POOR WOUND HEALING RICKETS (BONES BEND) (b) Iron LACK OF EGGS, MEAT, GREEN VEGETABLES IN DIET ANAEMIA TIREDNESS MENSTRUATION (PERIODS) PALE SKIN BRITTLE NAILS INABILITY TO ABSORB IRON (c) Protein • A severe lack of protein in the diet can causes kwashiorkor disease. LACK OF MEAT & DAIRY PRODUCTS IN DIET SWOLLEN STOMACH FATTY LIVER HAIR THINNING FLAKY SKIN LOSS OF MUSCLE MASS WEAKER BONES STUNTED CHILD GROWTH • The disease marasmus is similar. However, it is caused by an inadequate energy intake in all forms, including protein. C. THE HUMAN ALIMENTARY CANAL Salivary gland Tongue Epiglottis Salivary glands Oesophagus (Gullet) Liver Stomach Gall bladder Pancreas Duodenum Ileum Colon Appendix Rectum Anus • The small intestine is made up of the duodenum and ileum. • The large intestine is made up of the colon, rectum and anus. D. VOCABULARY WORD INGESTION MECHANICAL DIGESTION CHEMICAL DIGESTION ABSORPTION ASSIMILATION EGESTION MEANING The taking of substances into the body through the mouth The breakdown of food into smaller pieces without chemical change to food molecules The breakdown of large, insoluble food molecules into small, soluble molecules The movement of food molecules and ions through the wall of the intestine into the blood The movement of digested food molecules into body cells, whey they are used, becoming part of the cells The passing out of food that has not been digested or absorbed, as faeces, through the anus E. FUNCTIONS OF THE DIFFERENT ORGANS ORGAN FUNCTION MOUTH • • Ingestion and chewing Carbohydrate digestion starts here OESOPHAGUS • Lined with mucus to help swallowing STOMACH • • • Acid kills pathogens in food Acid provides an optimum pH for digestive enzymes to work Protein digestion starts here LIVER • Produces bile GALL BLADDER • Stores bile • Produces all types of digestive enzyme: PANCREAS - carbohydrase protease lipase SMALL INTESTINE • • Digestion Absorption of digested food LARGE INTESTINE • Absorption of water ANUS • Egestion of faeces F. COMPARING CHEMICAL DIGESTION & MECHANICAL DIGESTION CHEMICAL DIGESTION MECHANICAL DIGESTION Involves enzymes X Breaks down molecules X Chemically changes the food molecules Produces soluble molecules X X G. DIGESTIVE ENZYMES ENZYME AMYLASE WHERE IT IS PRODUCED SALIVARY GLANDS (MOUTH) WHAT IT BREAKS DOWN WHAT IS PRODUCED STARCH MALTOSE PROTEIN AMINO ACIDS GLYCEROL & FATTY ACIDS GLUCOSE PANCREAS PROTEASE STOMACH PANCREAS LIPASE PANCREAS LIPID (FAT) MALTASE PANCREAS MALTOSE • Amylase and maltase are carbohydrase enzymes. • There are two types of protease enzymes that you need to know about: - Pepsin acts in the stomach at a low optimum pH (acidic) - Trypsin acts in the small intestine at a higher optimum pH (alkaline) H. BILE • Produced by the liver and stored in the gall bladder. • Squirted onto food as it enters the small intestine from the stomach. • It is an example of mechanical digestion as the food is not chemically changed. Function 1: Emulsification Breaks up large fat globules into many smaller pieces Increased surface area so lipase enzyme can now digest fat faster Function 2: Neutralisation & Optimum pH • Bile is an alkali. This allows it to: - neutralise the acid in food coming from the stomach - provide the optimum pH for enzymes to work in the small intestine I. ABSORPTION • The small intestine is lined with millions of small finger-like projections called villi, to increase the surface area for absorption. • Digested food is absorbed in the small intestine. • Water is absorbed in both the small intestine and large intestine (colon). However, most water absorption happens in the small intestine. A Villus Thin wall = Close to blood capillaries = Short diffusion distance so fast diffusion of soluble food molecules into the blood Short diffusion distance so fast diffusion of soluble food molecules into the blood Many mitochondria = Lacteal (lymph vessel) = Carries fatty acids and glycerol to the heart so that fat does not enter the blood too quickly More respiration to release more energy for active transport Millions of small villi = Large surface area for fast diffusion J. CHOLERA • A disease caused by a bacterium, which causes severe diarrhoea. • Produces a toxin that acts on cells of the small intestine. SMALL INTESTINE Cl- Cl1. Toxin causes chloride ions (Cl-) to enter the small intestine Cl Cl - - ClCl Cl- - Cl- 2. Water potential in the small intestine decreases H2O 3. Water enters the small intestine by osmosis H2O H2O H2O H2O H2O H2O TO ANUS MORE WATER IN FAECES H2O K. TEETH Types Biting and cutting Holding and cutting Grinding, crushing and chewing Structure Enamel Crown Dentine Pulp cavity Gum Jawbone Cement Root Blood vessels Nerve Tooth Decay Enamel Dentine Bacteria in mouth respire sugars in food Pulp cavity Gum Acid produced Root Blood vessels Acid dissolves enamel and dentine Nerve Blood vessels and nerves are exposed = pain • Diet and regularly brushing help to prevent tooth decay.
