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The Digestive System: Breaking Down Food for Energy
- 1. 15 The Gastrointestinal System: Fuel for the Trip
- 2. • Takes in (ingests) raw material • Breaks it down (digests) both physically and chemically to usable elements • Absorbs those elements • Eliminates what isn't usable Gastrointestinal System
- 4. • Digestive tract, often called alimentary tract or canal, is muscular tube that contains organs of digestion • Tube begins with mouth and ends at anus Alimentary Canal
- 8. Figure 15-1 The digestive system.
- 9. • Mouth (oral cavity) is mucous-lined opening; also called buccal cavity • Lips (labia) act as door to cavity • Hard and soft palates create roof Oral Cavity
- 10. • Tongue acts as floor • Tongue's base and uvula act as boundary between oral cavity and pharynx Oral Cavity-Tongue is Border
- 11. • Uvula aids in swallowing, directing food toward pharynx and blocking food from entering nose • Tonsils help in fighting infection as part of lymphatic system • Teeth for grinding food Oral Cavity-Uvula, Teeth & Tonsils
- 12. Salivary Glands Begin Breakdown of Food • Sides of cavity created by cheeks • Mouth receives, tastes, mechanically breaks down, and begins process of chemical breakdown of food, adding saliva Oral Cavity
- 13. Figure 15-2 The mouth and oral cavity.
- 14. • Tongue is muscle that provides taste stimuli to brain, determines temperature, manipulates food, aids in swallowing • As tongue moves food around in oral cavity, saliva added to moisten and soften it, while teeth crush food Tongue
- 15. • Tongue pushes food into ball-like mass, called bolus, so it may be swallowed, passed to pharynx Tongue
- 16. • Lingual frenulum, membrane under tongue, keeps you from swallowing your tongue and aids in speaking Tongue-The Frenulum
- 18. Large Parotid Salivary Gland • Controlled by autonomic nervous system • Found slightly inferior and anterior to each ear; these swell when you get mumps Salivary Glands-3 Pairs
- 19. Sublingual and Submandibular Salivary Gland • Sublingual salivary glands: located under tongue • Submandibular salivary glands: on both sides along inner surfaces of mandible, or lower jaw Salivary Glands-3 Pairs
- 20. *Sight of food can stimulate secretion of saliva* • Salivary glands produce 1–1.5 liters of saliva daily • Saliva is 99.4% water; contains antibodies, buffers, ions, waste products, and enzymes Salivary Glands
- 21. Salivary Amylase breaks down Carbohydrates • Enzymes are biological catalysts to speed up chemical reactions • Salivary amylase: speeds chemical activity of breaking down carbohydrates Salivary Glands-Enzymes
- 22. Ptyalin converts starches to simple sugars • Enzymes are biological catalysts to speed up chemical reactions • Ptyalin: specific salivary amylase that converts starches to simple sugars Salivary Glands-Enzymes
- 23. • After eating, saliva cleans oral surfaces, reducing amount of bacteria that grows in mouth Less bacteria in the mouth Saliva Cleans Teeth
- 24. Figure 15-3 The salivary glands.
- 25. • Nasopharynx: primarily part of respiratory system, • Oropharynx and laryngopharynx: act as passageway for food, water, and air • Epiglottis: covers trachea to prevent food from entering lungs, forcing food into opening for esophagus Pharynx-3 Parts
- 26. • Approximately ten inches long; connected to stomach • Extends from pharynx, through thoracic cavity, and diaphragm, connecting to stomach in peritoneal cavity Esophagus
- 27. • Rhythmic contractions, called peristalsis, pushes food down esophagus Esophagus-Peristalsis
- 28. • Pharyngo esophageal sphincter, relaxes to open esophagus so food can enter • Walls lined with stratified squamous epithelium that secrete mucus to make walls slippery Esophagus
- 29. Condition called GERD caused by incompetent sphincter • At entrance to stomach is lower esophageal sphincter, or cardiac sphincter, opening door to stomach and closing to prevent acidic gastric juices from splashing into esophagus causing heartburn Esophagus
- 30. Located under the diaphragm, mid to left upper quadrant Stomach • Approximately ten inches long with diameter dependent on how much just eaten • Can hold up to four liters when filled • Rugae, or folds, help stomach expand and contract
- 32. • Liquids pass through fairly quickly • Carbohydrates move through quickly • Proteins take more time to pass through • Fats take longest, usually between 4 to 6 hours Stomach Movement of material through stomach
- 33. • FOUR REGIONS • Near heart is cardiac region, surrounding lower esophageal sphincter • Fundus, lateral and slightly superior to cardiac region, temporarily holds food as it enters stomach Stomach
- 34. • FOUR REGIONS • Body is mid portion of stomach • Funnel-shaped, terminal end of stomach called pylorus; most of work of stomach performed here; where food passes through pyloric sphincter into small intestine Stomach
- 35. Food “churned up” by muscles of the stomach • Muscular action works like cement mixer, achieved by three layers of muscles: longitudinal layer, circular layer, and oblique layer Stomach
- 36. • Churns food as it mixes with gastric juices excreted by gastric glands in gastric pits of columnar epithelial lining of stomach Stomach
- 37. • Works food toward pyloric sphincter through peristaltic activity of muscles • Both chemical and physical digestion occurs here Stomach
- 39. • Pepsin, chief digestive enzyme • Pepsin breaks down protein; HCl breaks down connective tissue Stomach-Gastric Juices
- 40. • HCl has pH of 1.5 to 2; effective at killing pathogens • Mucous cells generate thick layer of mucus shielding stomach from effects of HCl Stomach-Gastric Juices
- 41. • Stomach also secretes intrinsic factor, allowing vitamin B12 to be absorbed Stomach-Vitamin 12 Absorbed
- 42. Table 15-1 Gastric Glands and Their Functions
- 43. • Activity controlled by parasympathetic nervous system, particularly vagus nerve • Vagus nerve stimulation increases motility and secretory rates of gastric glands Stomach
- 44. Three Phases Gastric Juice Production
- 45. Cephalic phase Sensory stimulation (sight or smell of food) stimulates parasympathetic nervous system via medulla oblongata, stimulating release of gastrin which travels through bloodstream and reaches stomach, stimulating gastric gland activity Gastric Juice Production
- 46. Gastric phase •Two-thirds of gastric juices secreted as food enters stomach and distends, signaling stomach to secrete more gastric fluid Gastric Juice Production
- 47. Intestinal phase •Food enters duodenum, distending and sensing acidity, causing intestinal hormones to be released, slowing gastric gland secretions; lasts until bolus leaves duodenum Gastric Juice Production
- 48. Figure 15-9 Mechanisms of peptic ulcers and GERD
- 49. • Located in central and lower abdomen • Functions as major organ of digestion; where most of food digested Small Intestine
- 50. • Small in diameter, not length; longest section of alimentary canal; length up to 20 feet and diameter ranging from 4 cm where it connects to stomach and 2.5 cm where it meets large intestine Small Intestine
- 51. Walls secrete digestive enzymes, important for final stages of chemical digestion, and two hormones that stimulate pancreas and gallbladder to act, and control stomach activity Figure 15-10 The small intestine.
- 52. Villi in small intestine increase surface area for absorption • 80% of absorption of usable nutrients occurs when chyme comes in contact with mucosal walls; amino acids, fatty acids, simple sugars, vitamins, and water are all absorbed here into bloodstream and cells Small Intestine-Villi
- 53. • Remaining 20% absorbed in stomach • Any residue not utilized in small intestine sent to large intestine for removal from body Small Intestine
- 54. Duodenum:, located near head of pancreas; Jejunum: middle section, 2.5 m long Ileum: terminal end, 6– 12 feet long; attaches to large intestine at ileocecal valve Small Intestine-3 Sections
- 55. • Pancreas and gallbladder add secretions: bile from gallbladder • Pancreatic juice from pancreas • Bile emulsifies fat, making fat disperse in water Small Intestine-Pancreas & Gallbladder
- 56. • Mechanical and • Chemical irritation of acidic chyme, plus • Distention of intestinal walls, creates localized reflex action that causes release of enzymes and two hormones Small Intestine
- 57. • Secretin from duodenum stimulates secretion of enzymes and sodium bicarbonate from pancreas, which neutralizes acidic chyme • Cholecystokinin (CCK) secreted by duodenum stimulates gallbladder activity Small Intestine-2 Hormones
- 58. Table 15-2 Hormones in the Digestive Process
- 59. • Muscular action occurs in two ways • Segmentation causes mixing of chyme and digestive juices like cement mixer • Peristalsis moves food toward large intestine Small Intestine Chyme
- 60. Acinar cells secrete digestive enzymes in the small intestine • Digestive enzymes needed to complete chemical digestion are produced by exocrine cells Small Intestine
- 61. Nutrients travel to Liver before going to the body • Capillaries absorb and transport sugars (result of carbohydrate digestion) and amino acids (result of protein digestion) to liver for further processing before being sent throughout body Small Intestine
- 62. • Glycerol and fatty acids (obtained from fat digestion) are now a white, milky substance called chyle • Chyle goes directly into lymphatic system for distribution into bloodstream Small Intestine
- 63. Take a Break
- 64. • Beginning at junction of small intestine, ileocecal orifice, and extending to anus is large intestine, bordering small intestine Large Intestine
- 65. Large Intestine
- 66. Approximately five feet long and 2.5 inches in diameter; divided into three main regions: cecum, colon, and rectum Pouch-shaped structure, cecum, receives undigested food and water from ileum Figure 15-12 The large intestine.
- 67. • Some of water used in digestion and electrolytes reabsorbed in cecum and ascending colon; water absorbed is small amount, but crucial to maintaining proper fluid balance Large Intestine
- 68. • Attached to cecum • Three inches long, slender, hollow, deadend tube lined with lymphatic tissue Appendix
- 69. • Reservoir for useful bacteria to replace bacteria lost in intestines as result of diseases Appendix
- 70. • If becomes blocked or inflamed, causes appendicitis and must be treated with either antibiotics or surgical removal Appendix
- 71. • Four sections of colon: • • • • • Ascending, Transverse, Descending, and Sigmoid Ascending colon travels up right side to level of liver Large Intestine
- 72. • Transverse colon travels across abdomen just below liver and stomach • Descending colon bends downward near spleen and travels to left side becoming sigmoid colon Large Intestine
- 73. • Sigmoid colon extends to rectum • Rectum opens to anal canal that leads to anus • Anus relaxes and opens to allow passage of solid waste (feces) Large Intestine
- 74. • Peristalsis continues in large intestine, but at slower rate • As slower intermittent waves move fecal matter toward rectum, water is removed, turning it from watery soup to semisolid mass Large Intestine
- 75. • As rectum fills with feces, defecation reflex occurs, which causes rectal muscles to contract and anal sphincters to relax Rectum
- 76. • If fecal matter moves through too rapidly, not enough water is removed and diarrhea occurs • Conversely, if fecal matter remains too long in large intestine, too much water is removed and constipation occurs Diarrhea/Constipation
- 77. • Bacteria in bowel play two important roles: • Help break down indigestible materials • Produce B complex vitamins and most of vitamin K needed for proper blood clotting Large Intestine
- 78. • Besides salivary glands found in mouth, other accessory organs needed for digestion: • Liver • Gallbladder • Pancreas Accessory Organs
- 79. • Weighs 1.5 kg, located below diaphragm; largest glandular organ in body, and largest organ in abdomino pelvic cavity • Organ performs many functions vital to life Liver
- 80. • Divided into large right lobe and smaller left lobe; right side has anterior lobe and two smaller, inferior lobes Liver
- 81. • Receives about 1.5 quarts of blood every minute from portal vein (carrying blood full of end products of digestion) and hepatic artery (providing oxygen-rich blood) Liver-Portal Vein
- 83. Liver-Functions
- 84. Liver-Functions
- 85. Liver-Functions
- 86. • Secretion of hormone secretin stimulates bile production, critical liver digestive function Liver and Bile Production
- 87. • Salts found in bile act like detergent, breaking fat up into tiny droplets; process called emulsification, making work of digestive enzymes easier Liver and Bile Production
- 88. • Bile helps absorb fat from small intestine and transports bilirubin and excess cholesterol to intestine for elimination Liver and Bile Production
- 89. • Bile leaves liver via hepatic duct, travels through cystic duct to gallbladder, and is stored there until needed by small intestine Gallbladder Stores Bile
- 90. • Sac-shaped organ, 3 to 4 inches long, located under liver's right lobe Gallbladder
- 91. • While storing bile absorbs much of its water content, making it 6 to 10 times more concentrated; if too much water reabsorbed, bile salts may solidify into gallstones Gallbladder and Gallstones
- 92. • Fatty foods in duodenum cause release of CCK • Release causes smooth muscle walls of gallbladder to contract, squeezing bile into cystic duct, through common bile duct, and into the duodenum Gallbladder and Bile
- 93. Secretes insulin from cells in Islets of Langerhans • Plays role in digestion, as well as being endocrine gland • 6 to 9 inches long, located posterior to stomach, and extends laterally from duodenum to spleen Pancreas
- 94. • Exocrine portion secretes buffers and digestive enzymes through pancreatic duct to duodenum Pancreas
- 95. • Buffers needed to neutralize acidity of chyme, to pH ranging from 7.5 to 8.8, saving intestinal walls from damage Pancreas
- 98. • Generally include one or more of the following: • • • • Vomiting Diarrhea Constipation Abdominal pain Common Symptoms of Digestive System Disorders
- 99. • Vomiting • Protective mechanism, ridding digestive tract of irritant or overload of food that stimulates sensory fibers, sending signal to vomiting center in brain Common Symptoms of Digestive System Disorders
- 100. • Vomiting • Motor impulses sent to diaphragm and abdominal muscles to contract, squeezing sphincter at esophageal opening, and contents are regurgitated Common Symptoms of Digestive System Disorders
- 101. • Diarrhea • Fluid contents in small intestine rushed through large intestine without reabsorbing enough water • Proper absorption of electrolytes and nutrients prevented; can cause serious problems Common Symptoms of Digestive System Disorders
- 102. • Diarrhea • Frequent loose and watery bowel movements • Caused by infection, poor diet, toxins, food allergies or irritants, and stress Common Symptoms of Digestive System Disorders
- 103. • Constipation • Opposite of diarrhea; feces pass too slowly through colon and too much water is reabsorbed; stool becomes hard, dry, difficult to pass Common Symptoms of Digestive System Disorders
- 104. • Constipation • May be over stimulation of musculature of intestine creating more narrow passage for material Common Symptoms of Digestive System Disorders
- 105. • Constipation • May be musculature has become flaccid or slow as often found in bedridden geriatric patients Typical “FOS” Xray Common Symptoms of Digestive System Disorders
- 106. • Constipation • Dietary changes with more liquid, more roughage, reestablishment of regular bowel habits, avoidance of stress/tension, moderate exercise can contribute to improving condition Common Symptoms of Digestive System Disorders
- 107. • Constipation • Chronic use of laxatives and enemas should be avoided; may aggravate existing conditions or create new ones Common Symptoms of Digestive System Disorders
- 108. • Pain Large amount of gas can cause temporary pain until released • Can be sharp, dull, localized, diffuse, radiating, occasional, or constant • Severity of pain does not always indicate severity of disease Common Symptoms of Digestive System Disorders
- 109. • Pain • Stomach cancer may initially present with relatively mild form of indigestion • Any pain from GI tract should be investigated Common Symptoms of Digestive System Disorders
- 110. Review SOAP Note on Gastrointestinal Disease Watch video in class (not available online) Case Study