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The Digestive System 1 Functions • Chemical and physical breakdown of nutrients • Elimination of solid waste • Absorption of nutrients into bloodstream 2 2 Types of Digestion --Mechanical Digestion is physical. • Chew, tear, grind, mash, mix • Occurs in the mouth (teeth & tounge) • Occurs in stomach (churning and mixing) 3 2 Types of Digestion – Chemical • Catabolic reactions • Enzymatic hydrolysis –Carbohydrate- in mouth with salivase & intestines with carbohydrase –Protein- in stomach with protease –Lipid- in small intestines with bile 4 Digestion • Phases – – – – – Ingestion Movement Digestion Absorption Further digestion 5 Terms to know • Alimentary canal – 30-33 ft. long, runs from mouth to anus • Digestion – chemical breakdown of nutrients (begins in mouth, but mostly in stomach) • Ingestion – taking in of nutrients through the mouth • Absorption – passing of materials through alimentary wall to bloodstream • Defecation – release of solid waste through anus 6 Phases of Digestion 7 Digestive System Organization • Gastrointestinal (Gl) tract (Alimentary canal) – Tube within a tube – Structures • • • • • • • • Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Rectum Anus 8 Digestive System Organization • Accessory structures – Not in tube path – Organs • Teeth • Tongue • Salivary glands • Liver • Gall bladder • Pancreas 9 Anatomy of the Mouth and Throat 10 Human Deciduous and Permanent Teeth 11 Dorsal Surface of the Tongue 12 The Major Salivary Glands 13 Deglutition • Deglutiton – act of swallowing • Peristalsis – wavelike contractions that move the nutrients • Uvula – bundle of nerves to alert throat that food is entering 14 Deglutition • Pharnyx – common passageway for food and air. – Branches into trachea (air) and esophagus (food and liquid) • Epiglottis – flap that blocks either tube to prevent materials from going down the wrong tube. (If this doesn’t work you choke.) 15 Esophagus • Usually collapsed (closed) • Functions – Carry food and liquid to stomach through peristalsis • Features – Long, hollow muscular tube – Dimensions – 2cm by 25 cm 16 Peristalsis and Segmentation 17 Stomach • Usually “J” shaped • Functions – most of chemical breakdown occurs here • Rugae – ridges on inside – allows for increased surface area and increased expansion • chyme – slushy mixture – dissolved bolus 18 Stomach • Four regions – Fundus – upper curve, stores excess bolus for digestion – Body – main part of stomach, where digestion occurs (makes bolus into chime) – Cardia – upper end, produces mucus to coat lining of stomach – Pyloric – last section before small intestine, where acidity in chyme is neutralized 19 Anatomy of the Stomach 20 Small Intestine • Functions – absorption of nutrients into bloodstream • Regions – Duodenum – Jejenum – Ileum • Movements – Peristalsis 21 Small Intestine • Dimensions – 6m by 4cm-25cm • Longest part of alimentary canal 22 Structure of the Villi in the Small Intestine 23 Small Intestine • Requires pancreatic enzymes & bile to complete digestion 24 Large Intestine • Function – reabsorption of water form chime and compaction of waste into feces (solid waste) 25 Large Intestine • Regions – Rectum – storage of feces until release through anus – Cecum - appendix – Colon – has 3 regions, main part of large intestine • Ascending • Transverse • Descending – Anal canal 26 Anatomy of the Large Intestine 27 Feces Formation and Defecation • Chyme dehydrated to form feces • Feces composition – – – – – Water Inorganic salts Epithelial cells Bacteria Byproducts of digestion • Control – Parasympathetic – Voluntary • Defecation – Peristalsis pushes feces into rectum – Rectal walls stretch 28 Liver • Functions – blood cell formation, blood detoxification, bile (emulsifies fats) formation • Features – lobed, doesn’t grow much from birth to death • 4 Lobes – – – – Left Quadrate Caudate Right • Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein 29 Liver – Detoxifies/removes • Drugs • Alcohol – Stores • • • • Gycolgen Vitamins (A, D, E, K) Fe and other minerals Cholesterol – Activates vitamin D – Metabolizes absorbed food molecules 30 The Duodenum and Related Organs 31 Gallbladder • Functions – storage of bile • Features – small, pear-shaped organ; found in lobes of liver; muscular 32 Appendix • Functions – may have been a 2nd stomach; new research shows it may make digestive enzymes produced no where else in the body • Features – 7-9 cm (varies); redish, wormlike sac; open only at one end; attached to cecum 33 The Organs and Positions in the Abdominal Cavity 34 Structures of the Alimentary Canal 35 Crohn’s Disease 36 Acid Reflux • Stomach acid flows backwards causing irritation. • Symptoms – burning pain in the chest after eating or lying down 37 Gastritis • Inflammation of the stomach lining due to infection, injury, regular use of NSAIDs, too much alcohol • Symptoms - upper stomach pain, nausea, vomiting 38 Ulcers • A sore on the lining of the esophagus, stomach, or small intestine • Caused by damage due to stomach acid • Symptoms – upper abdominal pain 39 Diverticulitis • Inflammation or infection of the pouches of the intestine • More common after 40 • Symptoms – abdominal pain, fever, nausea, change in bowel movements 40 Gastric Bypass surgery 41