digestive system n.
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  1. DIGESTIVE SYSTEM • Digestion is the break down of foods into nutrients for the body to use. • Food is broken down by two processes: • chemical digestion is the chemical break down of foods • mechanical digestion is the chewing, mixing, churning break down of foods

  2. Mouth- salivary glands produce and release saliva; it helps moisten mouth • ptyalin- enzyme found in saliva- chemical substance that breaks down starches in foods into simple sugars • tongue- moves food around & mixes it with saliva • 4 types of taste buds (sweet, sour, bitter, salty) • flavor of food is mixture of taste, texture, & odor • chewed food is moved to the back of mouth by tongue • epiglottis- small flap of tissue that automatically covers the windpipe as food goes down

  3. Esophagus- Greek word meaning to carry what is eaten • 25 cm long • mucous glands line the wall to keep food moist & help move along the digestive system • takes 4 to 10 seconds for food to move down to the stomach • peristalsis- waves of muscular rhythmic contractions; move food downward with a squeezing actions; this allows you to swallow even when you are laying down

  4. Stomach- J shaped organ • food enters and cells in stomach wall release a fluid called gastric juice (juice contains hydrochloric acid (HCl), enzymes like pepsin, and mucous • specialized cells in the walls of the stomach release about 2 liters of HCl each day; HCl destroys bacteria present in food • food undergoes both mechanical (peristalsis) & chemical digestion (pepsin & HCl) • food moves through stomach in 2 to 4 hours and changes into thin, watery liquid called chyme

  5. Small Intestine- 2.5 cm in diameter, measures about 4 m to 7 m • food is slowly released from the stomach as chyme • most of digestion occurs here • intestinal juices are released from the cells lining the wall • inner lining looks like wet velvet and is covered with villi- tiny fingerlike structures that increases the surface area enabling more food to be absorbed • when undigested & unabsorbed materials leave the small intestine, it is basically free of nutrients; water & cellulose are left

  6. DIGESTIVE HELPERS- food NEVER goes through these organs but they aid in digestion. • Liver- located to the right of the stomach • largest & heaviest organ in the body; • produces bile & stored in the gall bladder • Gall Bladder- bile is released to break up large fat particles in the small intestine • Pancreas- soft triangular organ located between stomach & small intestine • helps break down proteins, starches & fats • also produces insulin a hormone that helps regulate sugar

  7. Large Intestine-horseshoe shaped about 7.5 cm in diameter and 1.5 m long • folds over the coils of the small intestine • main job is to absorb water from undigested mass • helpful bacteria feed on undigested materials like cellulose to make vitamins K (blood clotting) & B (vitamins B, niacin, thiamine for nervous system) • bacteria produces gas • unabsorbed & undigested materials change into solid mass called feces or stool

  8. Rectum- last section of the large intestine; stores feces until expelled • Anus- an opening at the end of the rectum through which wastes are excreted