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Digestive System Digestive System • A group of organs that work together to break down food so that it can be used by the body. • Digestive Tract: organs the food passes through; includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus. • Also includes liver, gall bladder, pancreas, and salivary glands. • Takes food about 24 hours to pass through the digestive tract. Breaking Down Food • Digestion: the process of breaking down food into a form that can pass from the digestive tract to the bloodstream. • Two types of digestion: 1. Mechanical- breaking, crushing, and mashing of food. 1. Chemical- large molecules are broken down into nutrients. • Enzymes are substances that break some nutrients into smaller particles. • Nutrients are substances needed for energy, growth, maintenance, and repair. 1. Carbohydrates (sugars) 2. Proteins (amino acids) 3. Lipids (fats) Mouth • Chewing creates smaller pieces of food that are wet and easier to swallow. • Teeth perform mechanical digestion. Covered in enamel, the hardest material in the body which protects the interior of teeth. • Saliva that is made in the salivary glands contains enzymes that begin chemical digestion of carbohydrates. Pharynx • Tube that connects mouth to esophagus. Esophagus • Food is pushed by the tongue into the throat that leads to this long straight tube. • Esophagus squeezes the food with muscle contractions called peristalsis (mechanical digestion). Stomach • Small, muscular, saclike organ attached to the lower end of the esophagus. • Continues mechanical digestion via peristalsis. • Tiny glands produce enzymes and acids that chemically break down food. • Stomach acid kills bacteria also. • Food is eventually reduced into chyme, a soupy mixture. Small Intestine • Muscular tube longer than you are tall! Called “small” due to small diameter. • Valve allows chyme to enter in small amounts. • Most chemical digestion occurs here. • Absorption of nutrients. • Covered in villi which absorb nutrients that enter the bloodstream to be delivered to cells in the body. Pancreas • Between the stomach and small intestine. • Food does NOT pass through. • Makes enzymes and bicarbonate (acid neutralizer) that protect the small intestine. • Also makes hormones that regulate blood sugar. Liver • Reddish, brown organ located toward the right side of the body. • Food does NOT pass through. • Makes bile to break up fat, stores nutrients, and breaks down toxins. • Detoxifies many chemicals, such as alcohol and drugs. Gall Bladder • Temporarily stores the bile made by the liver. • Bile breaks down large fat droplets so more of the fat can be exposed to digestive enzymes. Large Intestine • Most of the water in the leftover chyme is absorbed here. • Water and indigestible materials are stored and compacted into feces. • Cellulose which comes from plants we eat, cannot be digested. This “fiber” keeps feces soft and moving through the intestines. • Rectum stores feces until elimination. • Anus is the opening through which the feces pass out. 1.________________________________ 2.________________________________ 1 3.________________________________ 2 4.________________________________ 3 5.________________________________ 6.________________________________ 4 9 10 6 11 7.________________________________ 5 8.________________________________ 7 9.________________________________ 8 10. ________________________________ 11. _________________________________