Digestion

Nitty Gritty Terms Intracellular Digestion: - digestion occurs within the cell Extracellular Digestion: - digestion occurs outside of the cell in body cavities (ex: sm intestine) - digestion occurs outside of the cell in body cavities (ex: sm intestine) Mechanical Digestion: - changing the size or shape of foods Chemical Digestion: - changing the chemical composition of foods (ex: converting a protein into several amino acids)

Digestive System Tasks Digesting (breaking down) large food particles into smaller particles. Digesting (breaking down) large food particles into smaller particles. mixing and moving food material mixing and moving food material Secreting enzymes into tube where digestion occurs Secreting enzymes into tube where digestion occurs Absorb nutrients & fluids Absorb nutrients & fluids Eliminate wastes Eliminate wastes

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Major Components Mouth (oral cavity) Pharynx (throat) Esophagus Stomach Small Intestine Large Intestine Rectum Anus

Mouth Salivary glands Stomach Pancreas (behind stomach) Large intestine Small intestine Rectum Gallbladder (behind liver) Liver Esophagus Pharynx Digestive System Section 38-2

Mouth Teeth Teeth Physically breakdown food Physically breakdown food Mechanical Digestion Mechanical Digestion Tongue Tongue Helps mix food w/ saliva Helps mix food w/ saliva Aids in swallowing Aids in swallowing Saliva Saliva Produced by salivary glands at back of mouth and under tongue Produced by salivary glands at back of mouth and under tongue Starts chemical digestion Starts chemical digestion of starches Salivary amylase Salivary amylase

Esophagus Muscular tube Muscular tube Connects mouth & stomach Connects mouth & stomach Peristalsis moves food from mouth to stomach Peristalsis moves food from mouth to stomach Epiglottis keeps food out of the windpipe (so it doesn’t reach the lungs). Epiglottis keeps food out of the windpipe (so it doesn’t reach the lungs).

Stomach Muscular sac Muscular sac Mixes food, enzymes (pepsin), and HCl Mixes food, enzymes (pepsin), and HCl Protein digestion Protein digestion Mucus is secreted (protective) Mucus is secreted (protective)

Mixing Chyme A thick mixture of food and gastric fluid A thick mixture of food and gastric fluid High acidity kills many pathogens High acidity kills many pathogens Mixed & moved by waves of stomach contractions Mixed & moved by waves of stomach contractions peristalsis peristalsis

Protein Digestion in Stomach High acidity of gastric fluid denatures proteins & exposes peptide bonds High acidity of gastric fluid denatures proteins & exposes peptide bonds Pepsin breaks proteins into fragments Pepsin breaks proteins into fragments

Small Intestine Long coiled tube w/ small diameter Long coiled tube w/ small diameter Contains glands that secrete digestive enzymes Contains glands that secrete digestive enzymes Digestion completed here Digestion completed here Site of nutrient & vitamin absorption Site of nutrient & vitamin absorption

Structures of Absorption of Nutrients Villi Villi Finger like projections Finger like projections Micro-villi Micro-villi Made of epithelial tissue (one-cell thick) Made of epithelial tissue (one-cell thick) Contain a lacteal ( a lymphatic system vessel) & many capillaries Contain a lacteal ( a lymphatic system vessel) & many capillaries Fatty acids & glycerol Fatty acids & glycerol Absorbed into lacteal & go to the circulatory system via lymph Absorbed into lacteal & go to the circulatory system via lymph Monosaccharides & amino acids Monosaccharides & amino acids Go to liver via bloodstream. Go to liver via bloodstream.

Large Intestine Short tube w/ wider diameter Short tube w/ wider diameter No digestion occurs here No digestion occurs here Function is water absorption Function is water absorption Moves waste via peristalsis Moves waste via peristalsis

Rectum Lower end of large intestine Lower end of large intestine Semi-solid waste (feces) stay here until egested via the anus Semi-solid waste (feces) stay here until egested via the anus

Accessory Organs Salivary Glands Salivary Glands Secrete saliva Secrete saliva Liver Liver Secretes bile (emulsifies fats) Secretes bile (emulsifies fats) Gallbladder Gallbladder Stores & secretes bile Stores & secretes bile Pancreas Pancreas Secretes digestive enzymes to small intestine Secretes digestive enzymes to small intestine Protease, lipase & amylase Protease, lipase & amylase

Digestive Enzymes Site Mouth Stomach Small intestine (from pancreas) Small intestine Site Mouth Stomach Small intestine (from pancreas) Small intestine Enzyme Role in Digestion Section 38-2 Salivary amylase Pepsin Amylase Trypsin Lipase Maltase, sucrase, lactase Peptidase Breaks down starches into disaccharides Breaks down proteins into large peptides Continues the breakdown of starch Continues the breakdown of protein Breaks down fat Breaks down remaining disaccharides into monosaccharides Breaks down dipeptides into amino acids.