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The Digestive System Chapter 15 Terminology… • Digestion: breaking down food molecules so the body can use the nutrients • Gastroenterology: branch of science dealing with S/F/D of stomach & intestines • Peritoneum: serous membrane of abdomen • Visceral: surrounds organs • Parietal: lines abdominal cavity Digestive System • 2 parts • Gastrointestinal (GI) tract (alimentary canal) • Accessory digestive organs • 6 functions • Ingestion: taking in food/liquids • Secretion: water, enzymes, buffers • Mixing & propulsion: muscular contraction & peristalsis • Digestion: chemical=enzymes; mechanical=teeth & churning • Absorption: small nutrients enter cells • Defecation: output of undigested material (feces); mainly cellulose GI Tract • Continuous tube from mouth to anus through which food passes • Mouth pharynx esophagus stomach small intestine large intestine (colon) accessory accessory accessory accessory Accessory Organs • Aid in digestive process, but food does NOT pass through the structure • Teeth: mastication • Tongue: swallowing, food movement • Salivary glands: moistening food • Liver • Gallbladder • pancreas Mouth/Oral Cavity • • • • • • Lips Hard palate Soft palate with uvula Tongue Frenulum Salivary glands • Saliva=water, solutes, amylase • Teeth Teeth • a/k/a dentes • for mastication • Chewed food + saliva = BOLUS • Gum = gingiva • Deciduous = baby teeth • 6 months – 6 years • 20 teeth • Permanent = adult teeth • 6 years – adulthood • 32 teeth • 4 kinds: • • • • Incisors (flat): cutting Cuspids (canines): shredding Bicuspids (premolars): crushing/grinding Tricuspids (molars): crushing/grinding Pharynx • Oropharynx • Laryngopharynx • Swallowing causes… • Soft palate to close nasopharynx • Epiglottis to close larynx Esophagus • Food passageway • Collapsable tube • rings of muscle • Cardiac sphincter: at base of esophagus where it meets stomach • Faulty sphincter may cause heart burn and/or GERD Stomach • Rugae: internal folds • 4 parts • • • • Cardia (with sphincter) Fundus Body Pylorus (with sphincter) • Cells • Chief cells: make pepsinogen • Parietal cells: make HCl to convert pepsinogen into pepsin *Food remains here 2-6 hours *Liquid food as it leaves the stomach is called CHYME *Forcible explusion of upper GI contents = vomiting Pancreas* • Pancreatic duct connects pancreas to duodenum (1st section of small intestine) • Secretes pancreatic juices • Water, salts, enzymes, sodium bicarbonate (buffer) Liver* & Gallbladder* • Liver • • • • ~ 3 lbs (2nd largest organ) Makes bile (emulsifies fats) 2 lobes (right & left) Detoxifies blood • Gallbladder • Hangs on liver • Stores bile • Gallstones may develop if bile crystallizes Small Intestine • 1 inch in diameter • Approx. 10 feet long • 3 segments • Duodenum (~10 inches) • Jejunum (~3 feet) • Ileum (~6 feet) • Lined with villi & microvilli (projections that increase surface area by 600x) • Chyme remains here 3-5 hours • 90% of nutrient absorption occurs here Large intestine • 2.5 inches in diameter • Approx. 5 feet long • 4 parts • Cecum (pouchlike with appendix) • Colon (ascending, transverse, descending, sigmoid) • Rectum • Anal canal • Food remains here 3-10 hours • Water absorption occurs here Defecation reflex • Emptying the anus is a spinal cord reflex • Internal sphincter is relaxed • External sphincter is controlled by YOU • Food passes too large intestine = stool) • Food passes too large intestine = stool) quickly through diarrhea (watery slowly through constipation (dry Disorders • Appendicitis: inflammation of appendix • Removal = appendectomy • Hepatitis: inflammation of liver • Classified as STD • A, B, C, D, E • Ulcers: sores in GI tract • Duodenal = occur in duodenum • Peptic/Gastric = stomach • Anorexia: eating disorder resulting from lack of eating • Bulemia: eating disorder resulting from binging & purging Healthy liver Hepatitis liver Nutrition • Macronutrients are broken down by the digestive system into micronutrients • Carbohydrates (digest fastest) simple sugars • Proteins amino acids • Fats/Lipids (digest slowest) fatty acids Carbohydrates • Main energy source for the body • Food sources: fruits, vegetables & grains *Cellulose is a complex carb that humans cannot break down; it makes up fiber/roughage Proteins • Needed for repair, enzyme production, building muscle, making hormones • Food sources: meat, dairy, nuts *some essential amino acids come from food Lipids • Main source of energy storage • Food sources: fats, oils, lipids, cholesterol Vitamins (p. 434) • Organic compounds that are required in small amounts for proper metabolism • 2 types: • Fat soluble – A, D, E, K • Water soluble – B, C Minerals (p. 435) • Inorganic elements that are required in small amounts for proper metabolism • 2 types: • Major minerals – Ca, P, K, S, Na, Cl, Mg • Trace minerals – Fe, Mn, Cu, I, Co, Zn, F, Se, Cr