Human Digestive System PDF

## HUMAN DIGESTIVE SYSTEM ### PROCESS OF DIGESTION: 1. Ingestion 2. Digestion 3. Absorption and Transportation 4. Assimilation 5. Oxidation 6. Storage 7. Excretion and Egestion ### DIGESTIVE SYSTEM - Involved in the breakdown of food. - Digestion: process of breaking down food. ### GROUPS OF ORGA...

## HUMAN DIGESTIVE SYSTEM ### PROCESS OF DIGESTION: 1. Ingestion 2. Digestion 3. Absorption and Transportation 4. Assimilation 5. Oxidation 6. Storage 7. Excretion and Egestion ### DIGESTIVE SYSTEM - Involved in the breakdown of food. - Digestion: process of breaking down food. ### GROUPS OF ORGANS IN THE DIGESTIVE SYSTEM: - **Gastrointestinal Tract**: a continuous tube that extends from the mouth to the anus. - **Accessory Digestive Organs** 1. Teeth 2. Tongue 3. Salivary Glands 4. Liver 5. Gall Bladder 6. Pancreas ### FUNCTIONS OF THE DIGESTIVE SYSTEM: 1. Ingestion: taking food into mouth. 2. Secretion: release of any liquid/chemicals into the lumen of the alimentary tract. 3. Mixing and Propulsion: churning and movement of food. 4. Digestion: mechanical and chemical breakdown of food. 5. Absorption: passage of digested products. 6. Defecation: elimination of feces ### LAYERS OF THE GI TRACT: 1. Mucosa: inner lining of the GI tract. - Epithelium: non-keratinized stratified squamous. - Simple columnar epithelium for secretion and absorption. - Exocrine cells: mucus & fluid secretion. - Endocrine cells: hormones. - Lamina propria: nutrient absorption. - Muscularis mucosae: digestion & absorption. 2. Submucosa: binds the mucosa to the muscularis. 3. Muscularis: produces voluntary swallowing. 4. Serosa: the superficial layer. ### THE MOUTH: 1. Hard Palate: forms most of the root of the mouth. 2. Soft Palate: forms the rest of the mouth's root. 3. Uvula: prevents swallowed food in the nasal cavity. 4. Cheeks: forms lateral wall of the oral cavity. 5. Molars: grinds food. 6. Premolars: crush and grind food. 7. Canines: tear food. 8. Incisors: cut food. 9. Oral Vestibule: space between cheeks, lip, gums, and teeth. 10. Superior Labial Frenulum: attaches superior lip to gum. 11. Fauces: opening between the oral cavity & oropharynx. 12. Tongue: forms the floor of the mouth. 13. Lingual Frenulum: limits tongue's movement. 14. Gingivae: gums; cover both sockets. 15. Inferior Labial Frenulum: attaches inferior lip to gum. ### CHIEKS AND LIPS - Keep food between teeth. ### SALIVARY GLANDS - Secretes saliva. ### TONGUE - Extrinsic tongue muscles: move tongue from side to side and in and out. - Intrinsic tongue muscles: alter shape of tongue. - Taste Buds: serves as preceptors for gustation. - Lingual Glands: secretes lingual lipase. ### TEETH - Pulverize food. ### COMPOSITION AND FUNCTIONS OF SALIVA: 1. Water (99.5%): 2. Solutes (0.5%): - Sodium & Potassium - Chloride: activates salivary amylase. - Bicarbonate and phosphate ions: buffer acidic foods. - Urea & Unic Acid: help remove waste molecules. - Mucus: lubricates foods. - Immunoglobulin A: prevents attachment of microbes. - Lysozyme: kills bacteria. - Salivary Amylase: digestive enzymes for starch - maltose. ### THE TEETH: 1. Enamel: protects tooth from wear and tear. 2. Dentin: makes up majority of the tooth. 3. Pulp Cavity: pulp tissue containing nerves and blood. 4. Cementum: attaches root to the periodontal ligament. 5. Root Canal: extension of the pulp cavity. 6. Periodontal Ligament: helps anchor the tooth. 7. Apical Foramen: opening at the base of the root canal. ### DEGLUTITION: - Mechanism that moves food from the mouth to the stomach. ### PHARYNX: - Moves bolus from oropharynx to esophagus. ### ESOPHAGUS - Permits entry of bolus. ### PERISTALSIS: - Progression of coordinated contractions and relaxations pushes bolus onwards. ### STOMACH: - J-shaped enlargement of the GI tract. - Four main regions: 1. Cardia 2. Fundus 3. Body 4. Pylorus: only opens when digested food exits the stomach. - Rugae of Mucosa: increases surface area of the stomach. ### FUNCTIONS (STOMACH): - Serves as reservoir for food before release into the small intestine. - Secretes gastric juice. - HCl: kills bacteria and denatures protein. - Pepsin: digestion of protein. - Intrinsic Factor: absorption of Vit B12. - Gastric Lipase: digestion of triglycerides. - Secretes gastrin into the blood. - Hormone that will induce the secretion of gastric JUICE. ### GASTRIC JUICE: - Is the combined secretions of mucous cells, parietal cells, and chief cells. ### HISTOLOGY OF THE STOMACH: - Surface Mucous Cell: secretes mucus. - Mucous Neck Cell: secretes mucus. - Parietal Cell: secretes hydrochloric acid & intrinsic factor. - Chief Cell: secretes pepsinogen & gastric lipase. - G Cell: secretes the hormone gastrin. ### SURFACE MUCOUS CELLS: - Barrier that prevents digestion of the stomach wall. ### MUSCULARIS: - Forces chyme into the pyloric sphincter. - Pyloric Sphincter: regulates passage of chyme. ### THE PANCREAS, LIVER AND GALL BLADDER: - Pancreas: delivers pancreatic juice to assist in absorption. - Liver: produces bile necessary for the emulsification and absorption of lipids. - Gall Bladder: stores, concentrates, and delivers bile. ### ACINI: - The exocrine portion of the pancreas - secretes pancreatic juice. ### PANCREATIC ISLETS: - The endocrine portion of the pancreas - secretes hormones glucagon, insulin, somatostatin, and pancreatic polypeptide. ### COMPOSITION AND FUNCTION OF PANCREATIC JUICE: - Sodium Bicarbonate: buffers acidic gastric juice. - Pancreatic Amylase: starch digesting enzyme. - Pancreatic Proteases: trypsine, chymotrypsine, carboxypeptidase, elastase - digest proteins to peptides. - Pancreatic Lipase: triglyceride digesting enzyme. - Ribonuclease and Deoxyribonuclease: nucleic acid digesting enzymes into nucleotides. ### LIVER: - Heaviest gland of the body, second to skin in terms of size. - Gall Bladder: pear-shaped sac located in a depression of the posterior surface of the Liver. ### FUNCTIONS OF THE LIVER AND GALL BLADDER: - Bile: yellow, brownish, or olive-green liquid. - Bile Salts: emulsification of large lipid globules - aid in lipid absorption. - Bilirubin: produces stercobilin giving feces their normal brown color. ### SMALL INTESTINES: - A long tube where most digestion and absorption of nutrients occur. - Absorbs 90% of nutrients and water that passes through the digestive system. ### INTESTINAL GLANDS: - Secretes intestinal juice to assist in absorption. ### GOBLET CELLS: - Secretes mucus. ### CHIERO ENDOCRINE CELLS: - Secrete secretin, cholecystokinin and glucose-dependent insulinotropic peptide. ### PANETT CELLS: - Secrete lysozyme. ### DUODENAL GLANDS: - Secrete alkaline fluid. ### CIRCULAR FOLDS: - Increases surface area for absorption & digestion. ### VILLI: - Finger-like projections that serves as absorptive sites. ### MICROVILLI: - Membrane-covered projections of absorptive epithelial cells. ### MUSCULARIS: - Mixes chyme with digestive juices and brings food into contact with mucosa for absorption. ### SEGMENTATION: - Moves chyme with muscular tremors along. ### MIGRATING MOTILITY COMPLEX: - Moves chyme toward the ileocecal sphincter. ### SMALL INTESTINES ANATOMY: 1. Duodenum 2. Jejunum 3. Ileum ### LARGE INTESTINES ANATOMY: 1. Cecum 2. Colon 3. Rectum ### FUNCTIONS: - Haustral churning, peristalsis, and mass peristalsis drive contents of colon into rectum and defecation. - Formation of feces and defecation. ### LUMEN: - Breaks down undigested carbohydrates, proteins, and amino acids into products that can be expelled in feces. ### MUCOSA: - Lubricates colon, protects mucosa. ### MUSCULARIS: - Haustral Churning: moves contents from haustrum to haustrum by muscular contractions. - Peristalsis: moves contents along the length of colon. - Mass Peristalsis Reflex: forces contents into sigmoid colon. - Defecation Reflex: eliminates feces. ### PHASES OF DIGESTION: 1. Cephalic Phase: prepares the mouth and stomach for food that is about to be eaten. 2. Gastric Phase: presence of food in the stomach promotes gastric juice secretion and gastric motility. 3. Intestinal Phase: food is digested in the intestine. ### GASTRIN: - Promotes secretion of gastric juice. ### SECRETIN: - Stimulates secretion of pancreatic juice and bile. ### CHOLECYSTOKININ: - Stimulates secretion of pancreatic juice rich in digestive enzymes and ejects bile from gall bladder. ### AGING CAUSES: - Decreased in secretory mechanisms, decreased motility, and loss of strength and tone. ### SPECIFIC CHANGES INCLUDE: - Loss of taste, pyorrhea, hernias, peptic ulcer disease, constipation, hemorrhoids, and diverticular diseases. ### CHANGES IN THE SMALL INTESTINE INCLUDE: - Duodenal ulcers, malabsorption, and mal-digestion.