Nutrition is the process of taking in molecules (food) from the environment and changing into usable forms. It is one of the life functions that were discussed in chapter 1. Nutrients are substance that can be used in metabolism. There are 6 types of nutrients; carbohydrates, fats, proteins, water, vitamins & minerals. Plants absorb minerals from the ground and animals obtain minerals by eating plants. This fact leads us to two different types of nutrition.

I. Types of Nutrition A. Autotrophic nutrition: make their own food 1. Photosynthesis- get energy from sun 2. Chemosynthesis- get energy from inorganic chemicals Example-- bacteria, plants on the bottom of ocean

B. Heterotrophic nutrition: can't make their own food 1. Steps for heterotrophic nutrition a. Ingestion- bringing food into the organism b. Digestion- process by which food molecules are broken down & absorbed 1. Mechanical digestion- chewing increases surface area for enzyme action 2. Chemical digestion- hydrolysis; carried out by digestive enzymes

c. Egestion- 2. The rest of the notes focus more on heterotrophic nutrition getting rid of indigestible matter; feces or stool

HUMAN DIGESTION SYSTEM (notes are arranged in terms of flow of food through the alimentary canal 1. MOUTH (oral cavity)- a. Mechanical digestion- name teeth b. chemical digestion- salivary glands (accessory organ) adds saliva, enzyme amylase (start of carbohydrate digestion) Starch (amylose), which is a polysaccharide-----> maltose (disaccharide) c. Bolus: mass of food that has stuck together in mouth

2. PHARYNX-(back of throat) swallowing reflex 3. ESOPHAGUS (gullet)- tube from mouth to stomach which bolus travels a. Epiglottis- blocks passage to trachea during swallowing b. Larynx- voice box at top of trachea which receives air, not food c. Peristalsis- muscular contractions move food along to cardiac sphincter

d. Cardiac Sphincter- "valve" between stomach and esophagus e. Vomiting- reverse peristalsis, cardiac sphincter opens and food moves up

4. STOMACH- thick walled, muscular sac, mechanical & chemical digestion occur here a. Pyloric glands in stomach- secrete mucus which covers the stomach lining & protects it from being digested b. gastric glands- secrete gastric juice which contain hydrochloric acid (HCI), water (H 2 O), pepsin or protease (enzymes that digests proteins starts) 1. the thought, sight, smell, taste + touch of food stimulates the flow of gastric juice

c. Chyme- solid food which is turned into a thin soupy acid liquid within stomach d. Ulcer- the stomach is digesting itself caused by a bacteria e. Pyloric sphincter- muscle that connects the stomach and small intestine

5. SMALL INTESTINE- a. Peristalsis- moves chyme along & mixes it with digestive enzymes b. intestinal juice is mixture of enzymes produced by intestinal gland 30 feet long, site where most digestion occurs

c. Pancreas- accessory gland produces pancreatic juice which is mixture of enzymes added to small intestine accessory gland produces bile which is a fluid which aids in the breakdown of fats (emulsification); is stored in the gallbladder then released into small intestine e. contents of small intestine have basic pH because of bile d. Liver- f. Villi- small finger like projections in the lining of the small intestine which absorb end products of digestion, increase surface area for absorption g. Appendix: joins small intestine with large intestine; small pouch that plays no part in digestion

6. LARGE INTESTINE- no digestion occurs here, water is reabsorbed a. Bacteria living here make vitamins b. feces are formed c. Rectum: store feces d. Anus: sphincter opens when stimulated by pressure; peristalsis pushes feces out-EGESTION occurs

SOME COMMON DIGESTIVE SYSTEM DISORDERS Ulcers – open, painful sore in stomach lining. Can bleed and sometimes eats through the stomach wall. Treated with diet and medication Tooth Decay – mouth bacteria can cause tooth decay. Brushing and flossing teeth at least once a day helps slow down the action of bacteria on food caught between teeth. Regular visits to your dentist are very important in preventing tooth decay and gum disease Appendicitis – an infection of the appendix, treatment is surgical removal of the appendix.

Diarrhea – condition in which feces do not remain in the large intestine long enough for the water to be absorbed. Can be caused by bacteria or viruses, emotional stress or eating certain foods. If it lasts for a long time the body becomes dehydrated resulting in weakness. Severe diarrhea can result in death Constipation – a condition where the feces remain in the colon too long. Can be caused by too little fiber or water in the diet.