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Digestive System Lesson Objectives • List four functions of the digestive system. • Describe the four layers of the digestive tract. • Describe the structure and functions of the organs of the digestive tract. • Describe the structure and functions of the accessory organs of the digestive tract. Digestive System Other names: -Alimentary Canal -Gastrointestinal (GI) Tract Functions of the Digestive System Ingest food Digest it –Mechanical –Chemical Absorb nutrients Excrete waste Overview of the Digestive System Mouth Pharynx Esophagus Stomach Small intestine Large intestine Rectum, anus Accessory organs --Salivary glands --liver --gallbladder--pancreas Four Layers of the Digestive Tract Mucosal layer (innermost) hormones, enzymes, mucus Submucosal layer nerves, glands, blood vessels Muscle layer - Circular and longitudinal Mixing, mashing action - Peristaltic action “wave-like” motion - Enteral nervous system Serosal layer (outermost) - Peritoneal membranes Peritoneal Membranes • Anchor organs • Behind the digestive organs –Mesentery and mesocolon • In front of organs –Greater or lesser omentum Peritoneal Membranes Greater omentum- “Lacy Apron” Mesentery Peristalsis • Waves of muscle contraction, relaxation • Pushes food from mouth toward anus • Peristaltic movements differ from organ to organ Oral Cavity = Mouth • Teeth: Mastication – 2 sets: • Deciduous: 20 “Milk teeth” • Permanent: 32 • Tongue: Swallowing – Forms bolus (food ball) • Salivary glands - Parotid - Submandibular (below jaw) - Sublingual (below tongue) Buccal cavity= gums to cheeks/lips The Tooth Three parts: 1. Crown = above gum(gingiva) 2. Neck= connects crown to root 3. Root= embedded in jaw (dentin), has pulp(sensation) Shape Shape and location indicate function Incisors = tear and grasp Cuspids (Canines) = tear and grasp Premolars (bicuspids) = grind molar = grind Tongue Two Roles 1. Positioning of Food a) Bolus (food ball) 2. Taste Sensation a) Taste buds (poison) Parts: Frenulum: anchor Sublingual blood supply Eating and Swallowing • Mouth – Hard and soft palates – Uvula (for swallowing) • Pharynx (throat) – Laryngopharynx – Oropharynx • Epiglottis: covers trachea • Esophagus - Esophageal sphincters Pharyngoesophageal Lower esophageal Borborygmus? •What is Borborygmus??? Functions of the Stomach • • • • • Regulates rate of gastric emptying Secretes gastric juice, HCl Secretes gastric hormones Digests limited amount of food Absorbs limited substances Parts of the Stomach • • • • • • • Fundus Body Rugae Lesser curvature Greater curvature Pylorus Pyloric sphincter Muscles of the Stomach • • • • Longitudinal Oblique Circular Mixing and mashing chyme • Peristalsis Stomach Structure: Mucosa • Mucous cells • Parietal cells - HCl - Intrinsic factor • Chief cells - Digestive enzymes • Chyme: pastelike mixture Small Intestine: Parts and Functions Parts (Dow Jones Industrials) (DJ Illy) - Duodenum - Jejunum - Ileum Functions -Digests -Absorbs -Secretes hormones and digestive enzymes Villi and Microvilli • Folds increase area for absorption • Inside composed of capillaries and lacteals • Deliveres to hepatic portal system and lymphatics Duodenum • 10 inches • Receives Chyme of stomach • Accessory organ secretions enter here • Where MOST DIGESTION and ABSORPTION OCCURS The Rest Jejunum (2nd Part) • 8 Feet Ileum (3rd Part) • 12 feet • Connects to Cecum of L.I. – Ileocecal valve • Contains Peyer’s patches -Control bacterial numbers of L.I. Large Intestine • 5 feet • Cecum – Vermiform appendix • Colon -Ascending -Transverse -Descending -Sigmoid • Rectum • Anal Canal Anus Functions of the Large Intestine • Absorption of water and electrolytes -Constipation: absorb too much water -Diarrhea: not absorbing enough water • Synthesis of vitamins by intestinal bacteria • Temporary storage of waste • Elimination of waste (feces) and gas (flatus) Landmarks of Large Intestine • • • • Hepatic flexure: curve near liver (right side) Splenic flexure: curve near spleen (left side) Anal canal has 2 sphincters Internal sphincter – (involuntary) • External sphincter – (voluntary), potty training Clinical Conditions: Stomach A. Gastric ulcer B. Hiatal hernia C. Nasogastric tube D. Gastric resection E. Pyloric stenosis F. Vagolytic effects Gastrostomy tube Clinical Conditions: Large Intestine A. Intestinal obstruction B. Colostomy C. Hemorrhoids D. Enema Accessory Digestive Organs • Liver • Gallbladder • Pancreas Liver Functions • • • • Synthesis of bile salts and secretion of bile Synthesis of plasma proteins Storage of glucose, fat-soluble vitamins Detoxification – Main organ for drug detoxification • Excretion of bilirubin, cholesterol, drugs • Metabolism of carbohydrates, protein, fats • Phagocytosis: Kupffer cells (hepatic macrophages) Hepatic Portal System • Liver processes end products of digestion • Discharging blood through hepatic veins and into Inferior Vena Cava Biliary Tree • Ducts connect liver, gallbladder, pancreas to duodenum • Hepatic ducts • Cystic duct • Common bile duct – Ampulla of Vater – Sphincter of Oddi Gallbladder • Pear-shaped sac -underside of the liver -concentrates and stores bile • Attached to common bile duct by cystic duct • Fat in the duodenum stimulates release of the hormone cholecystokinin (CCK) -CCK causes gallbladder to contract, eject bile into common bile duct and duodenum Bile • Formed from blood in the liver lobules • Assists in digestion of fat • Stored in gallbladder • Composition -Water -Cholesterol -Bile pigments -Salts Clinical Conditions • Celiac Disease – Unable to absorb certain nutrients • Gallstones • Bleeding – Loss of clotting factors (liver failure) • Esophageal varices – Bleeding into esophagus • Acute pancreatitis Lesson 23-2 Objectives • Explain the physiology of digestion and absorption. • Describe the effects of amylases, proteases, and lipases. • Describe the role of bile in the digestion of fats. • Describe five categories of nutrients. Nutrition Basics • Mechanical Digestion: change in size • Chemical Digestion: change in chemical composition • Food -Carbohydrates -Proteins -Fats -Vitamins and Minerals • Specific Enzymes for each type – Ending of –ase indicates enzymes Fats: Digestion and Absorption • Fats are insoluble in water. • Emulsification -Bile splits big fat globules into small ones. -Bile salts make fat watersoluble. • Digestion -Accomplished by lipases -End products: Fatty acids and glycerol, absorbed by lacteals Carbohydrates: Digestion and Absorption • Monosaccharides -Simple sugars, end products of digestion absorbed by villi • Disaccharides -Digested by disaccharidases to monosaccharides • Polysaccharides -Digested by amylases to disaccharides Proteins: Digestion and Absorption • Gastric HCl unravels strands of protein • Proteases digest protein into amino acids, which are absorbed into villi • Common proteases -Pepsin, stomach -Trypsin, pancreas -Chymotrypsin, pancreas -Enterokinase, duodenum Digestion and Absorption: Summary • Trace the flow of food from the mouth to the anus. • Point out entrance of each accessory organ into the digestive tract. Nutrition: Concepts to Know • Nutrition: Study of the relationship of food to body function • Five categories of nutrients – Carbohydrates – Proteins – Lipids – Vitamins – Minerals Nutrition Concepts: Carbohydrates Simple Sugars Complex Carbohydrates • Monosaccharides • Disaccharides • Polysaccharides • Consist primarily of starch and fiber • Most carbohydrate consumption should be in this form. Nutrition Concepts: Proteins • Essential amino acid: Not synthesized by the body; must be consumed • Nonessential amino acid: Synthesized in the body; not essential to consume • Complete protein: Contains all the essential amino acids • Incomplete protein: Does not contain all essential amino acids Nutrition Concepts: Fats • Saturated fatty acid: Solid at room temperature • Unsaturated fatty acid: Oil; liquid at room temperature • Essential fatty acid: Not synthesized by the body and must be consumed; linoleic acid is an important component of cell membranes Nutrition Concepts: Vitamins • Small organic molecules that help regulate cell metabolism • Fat-soluble vitamins – Vitamins A, D, E, and K – Can be stored in the body • Water-soluble vitamins – Vitamins B and C – Most are not stored by the body Nutrition Concepts: Minerals • Inorganic substances needed for normal body function • Sodium, chloride • Potassium • Calcium, phosphorus, magnesium • Iron • Iodine • Trace elements Appetite Control • Hypothalamus – Feeding center – Satiety center • Theories of satiety – Glucostat hypothesis – Lipostat hypothesis