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Digestive System -breaking down of food through enzymatic activity -elongated tube beginning at mouth & terminating at anus Functions: • ingest food • break down food • extract & absorb nutrients • eliminate wastes • Breakdown polymers to monomers 1) Lipids -glycerol & fatty acids 2) Carbohydrates -monosaccharides (glucose) 3) Protein -amino acids Bozeman Digestive System Digestion in the mouth -mastication (chewing) -mixed w/salivary amylase (breaks down carbohydrates) -lubrication • Control of digestive secretions: -only when food is present -under neurological control -touch receptors on tongue Salivary glands Digestive glands & enzymes: 1) Salivary glands -3 pairs of salivary glands… secrete saliva -1 pair secrete salivary amylase (breaks down starches)-parotid -2 pairs secrete mucin (lubricates mouth & causes adhesion of food particles)submandibular and sublingual -food leaving mouth is known as a bolus Salivary glands (a) The stomach wall has three layers of smooth muscle, each oriented in a different direction, that allow the stomach to churn and mix food with digestive secretions. 2) Esophagus Sphincter Longitudinal layer of muscle Sphincte r Digestive Organs Circular layer of muscle Oblique layer of muscle Stomach -mixes & stores food -digestion of protein -gastric glands secrete hydrochloric acid (HCI), pepsin, gastric lipase -HCI lowers pH to kill any bacteria -pepsin breaks down proteins - gastric lipase breaks down lipids -food leaving stomach is known as chime Khan Academy: Stomach Digestion in the stomach: • Mucus (Mucus) -protects stomach walls • HCL (Parietal) -soften proteins -lowers pH (0.8-2) Pepsin -protein to proteases (peptone & polypeptides) • Gastric lipase (Chief) -breaks down milk-cream, & egg yolk • Rennin (Chief) -breaks down milk (child stomach) Digestive Organs (cont.) The liver produces bile, which is stored in the gallbladder before being released into the small intestine. 3) Liver -2nd largest organ in body -secretes bile & sends it to gallbladder for storage -bile salts emulsify lipids -gatekeeper of blood -removal of toxins & keeps blood constituents constant Liver Gallbladder Pancreas (behind stomach) Small intestine The pancreas produces several digestive enzymes that act in the small intestine 4) Pancreas -pancreatic juices (alkaline) containing enzymes to break down carbohydrates, protein, & fats 5) Small intenstine -receives enzymes from pancreas & bile from gallbladder Digestion in the small intestine: -alkaline environment -pancreatic juices -villi & microvilli: absorption -bile component (cystic duct) -bile pigments, cholesterol, water, & bile salts Absorption in the S.I. Digestion in the large intestine: • Function -removes water, salts, & storage of non-digestible food -bacteria -help digest indigestible food -provide some vitamins What substances gets absorbed in the mouth and large intestine? In the mouth: -no food (only sugars) -some drugs and some alcohol -some glucose (most absorption) In the large intestine -water absorption Absorption mechanisms -osmosis -diffusion -active transport Routes of absorption -circulatory & lymphatic systems Passage of food -peristalsis -rhythmic contractions of smooth muscle tissue Peristalysis (LI)