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Introduction of digestive system .pdf
- 1. Digestive system Digestive system MoathNairat, MD Moath Nairat, MD
- 2. Function of thedigestive system Function of the digestive system • ingestion: taking food and liquid into mouth • Secretion: total about 7 liter into lumen • Mixing and propulsion: through GI muscle and peristalsis and motility • Digestion: Breakdown of ingested food (mechanical and chemical) • Absorption: Passage of nutrients into the blood • Metabolism: Production of cellular energy (ATP) • Defecation: waste substance leave the GI tract through anus
- 3. Organs of theDigestive System Organs of the Digestive System • Two main groups • Alimentary canal or gastrointestinal tract – continuous coiled hollow tube from mouth to anus(5-7 meter) • Accessory digestive organs: teeth ,tongue ,salivary gland ,liver ,gallbladder ,and pancreas
- 4. Organs of theDigestive System Organs of the Digestive System
- 5. Organs of theAlimentary Canal Organs of the Alimentary Canal • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Anus
- 6. Mouth (Oral Cavity)Anatomy Mouth (Oral Cavity) Anatomy • Lips (labia) – protect the anterior opening • Cheeks – form the lateral walls • Hard palate – forms the anterior roof • Soft palate – forms the posterior roof • Uvula – fleshy projection of the soft palate
- 7. Mouth (Oral Cavity)Anatomy Mouth (Oral Cavity) Anatomy • Vestibule – space between lips externally and teeth and gums internally • Oral cavity – area contained by the teeth • Tongue – attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum
- 8. Tongue Tongue • Dorsum (upperpart of tongue covered with papillae taste receptor and buds) • filiform papillae • fungiform papillae • circumvallate papillae • Paltine tonsil and lingual tonsil
- 9. Salivary glands -Parotid gland:In the parotid fossa, three main structures transverse this gland – facial nerve, external carotid artery, and retromandibular vein. The parotid duct opens near the upper 2nd molar tooth. The gland is completely serous. - Submandibular gland: Sitting most posteriorly in the submandibular triangle, it is supplied by the facial artery and vein. Submandibular ducts, which cross the lingual nerves, open on both sides of the tongue frenulum. It is mostly serous but partially mucus,. - Sublingual gland: The smallest salivary gland sits beneath the oral mucosa in the floor of the mouth. It has multiple small openings. This gland is almost completely mucus- secreting.
- 10. Teeth • Teeth (mechanical breakdown) –Incisors used for cutting – Canines used for stabbing and holding – Molars large surface area used for grinding • Primary or deciduous teeth 20 • Secondary or permanent teeth 32
- 11. Structure of Teeth Crown- exposed surface of tooth Neck - boundary between root and crown Enamel - outer surface (the hardest substance in the body 95% calcium salts) Dentin – bone-like, but noncellular(70% calcium salts) Pulp cavity - hollow with blood vessels and nerves Root canal - canal length of root gingival sulcus - where gum and tooth meet
- 12. Processes of theMouth Processes of the Mouth • Mastication (chewing) of food • Mixing masticated food with saliva to produse easy digestied food called bolus • Saliva contain 2 enzyme,salivary amylase and lingual lipase • Initiation of swallowing by the tongue • Allowing for the sense of taste
- 13. Layers of AlimentaryCanal Organs Layers of Alimentary Canal Organs • Submucosa •Just beneath the mucosa •Soft connective tissue with blood vessels, nerve endings, and lymphatics also contain submucosal plexus
- 14. Layers of AlimentaryCanal Organs Layers of Alimentary Canal Organs • Mucosa • Innermost layer • Moist membrane 1. Surface epithelium : secretion and absorbtion,renew every 5-7 days also contain enteroendocrine cells 2. Small amount of connective tissue (lamina propria): contain blood and lymphatic vessele also contain MALT 3. Small smooth muscle layer
- 15. Layers of AlimentaryCanal Organs Layers of Alimentary Canal Organs • Muscularis externa – smooth muscle 1. Inner circular layer 2. Outer longitudinal layer Between them is myenteric plexus • Serosa • Outermost layer – visceral peritoneum • Layer of serous fluid-producing cells (mesothelium)
- 16. Layers of AlimentaryCanal Organs Layers of Alimentary Canal Organs
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- 18. Pharynx Anatomy Pharynx Anatomy •Nasopharynx – not part of the digestive system • Oropharynx – posterior to oral cavity • Laryngopharynx – below the oropharynx and connected to the esophagus
- 19. Pharynx Function Pharynx Function •Serves as a passageway for air and food • Food is propelled to the esophagus by two muscle layers •Longitudinal inner layer •Circular outer layer • Food movement is by alternating contractions of the muscle layers (peristalsis)
- 20. Esophagus Esophagus • Runs frompharynx to stomach through the diaphragm( 25 cm) • Conducts food by peristalsis (slow rhythmic squeezing): contraction of circular layer above the food and contraction of longitudinal below the food • Passageway for food only (respiratory system branches off after the pharynx)
- 21. Esophagus - The esophagusis posterior to the larynx and trachea in the neck region and upper thorax. It travels on the right side of the descending aorta, passes through the diaphragm, and connects with the stomach. -There are also inner circular and outer longitudinal muscle layers. - The upper third is skeletal muscle (voluntary), middle third is mixed, and lower third is smooth muscle (involuntary). -esophagogastric junction is located approximately at the level of the diaphragm. Contractions of the diaphragm create sphincter- like effects, preventing reflux of stomach acids and content. The esophagogastric junction is a functional, not anatomical, sphincter.
- 22. Peristalsis in Esophagus Bolusof food Muscles relax, allowing passageway to open Stomach Muscles contract, constricting passageway and pushing bolus down Muscles relax Muscles contract Muscles relax Muscles contract
- 23. Stomach Anatomy Stomach Anatomy •Located on the left side of the abdominal cavity • Food enters at the cardioesophageal sphincter Site where food is churned into chyme Protein digestion begins
- 24. Stomach Anatomy Stomach Anatomy •Regions of the stomach •Cardiac region – near the heart •Fundus •Body •Phylorus – funnel-shaped terminal end • Food empties into the small intestine at the pyloric sphincter
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- 26. Stomach Anatomy Stomach Anatomy •Rugae – internal folds of the mucosa • External regions •Lesser curvature •Greater curvature
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- 28. Stomach Anatomy Stomach Anatomy •Layers of peritoneum attached to the stomach •Lesser omentum – attaches the liver to the lesser curvature •Greater omentum – attaches the greater curvature to the transverse colon which Contains fat to insulate, cushion, and protect abdominal organs
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- 31. Stomach Functions Stomach Functions •Acts as a storage tank for food • Site of food breakdown and mixing • Chemical breakdown of protein begins • Delivers chyme (processed food) to the small intestine
- 32. Specialized Mucosa ofthe Specialized Mucosa of the Stomach Stomach • Simple columnar epithelium • Mucous neck cells – produce a sticky alkaline mucus • Gastric glands – secrete gastric juice • Chief cells – produce protein-digesting enzymes (pepsinogens) • Parietal cells – produce hydrochloric acid and Intrinsic factor(B12 absorption) • Endocrine cells (G cell) – produce gastrin which stimulates both parietal and chief cells)
- 33. Structure of theStomach Mucosa Structure of the Stomach Mucosa • Gastric pits formed by folded mucosa • Glands and specialized cells are in the gastric gland region
- 34. Structure of theStomach Mucosa Structure of the Stomach Mucosa
- 35. Peritoneum • Is thelargest serous membrane of the body consist of mesothelium • Divide into 1. Parietal peritoneum: lines the wall of abdominopelvic cavity internally 2. Visceral peritoneum: cover some oh the organs in the cavity 3. The space between them contain fluid and called peritoneal cavity this cavity may be accumulated by several liters of fluid state called ascites
- 36. Membranes Membranes Mesenteries - doublesheets of peritoneum, surrounding and suspending portions of the digestive organs Peritoneal folds 1. falciform ligament:- attach the liver to anterior abdominal wall and diaphragm 2. Greater omentum - "fatty apron", hangs anteriorly from stomach, double layer encloses fat 3. Lesser omentum - between stomach and liver 4. Mesentery proper - suspends and wraps the small intestine 5. Mesocolon - suspends and wraps the colon, parts are i. transverse mesocolon ii. sigmoid mesocolon • Ascending and descending ,pancreas, first 2 parts of the duodenum and kidneys are Retroperitoneal structure
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- 38. Mesenteries • Greater omentum andtransverse colon reflected
- 39. Mesenteries • Superficial view ofthe abdominal organs
- 40. Small Intestine Small Intestine •The body’s major digestive organ • Site of nutrient absorption into the blood • Muscular tube extending form the pyloric sphincter to the ileocecal valve • Suspended from the posterior abdominal wall by the mesentery
- 41. Subdivisions of theSmall Intestine Subdivisions of the Small Intestine • Duodenum(25cm) •Attached to the stomach •Curves around the head of the pancreas •Fixed retroperitoneal structure • Jejunum (2.5m) •Attaches anteriorly to the duodenum • Ileum (3.5m) •Extends from jejunum to large intestine
- 42. Regions Regions of SmallIntestine of Small Intestine
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- 44. Duodenum and RelatedOrgans Liver Bile Gall- bladder Bile Duodenum of small intestine Acid chyme Pancreatic juice Intestinal enzymes Stomach Pancreas
- 45. Chemical Digestion inthe Small Chemical Digestion in the Small Intestine Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Source of enzymes that are mixed with chyme •Intestinal cells •Pancreas • Bile enters from the gall bladder
- 46. Villi of theSmall Intestine Villi of the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Fingerlike structures formed by the mucosa • Give the small intestine more surface area Figure 14.7a
- 47. Microvilli of theSmall Intestine Microvilli of the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Small projections of the plasma membrane • Found on absorptive cells Figure 14.7c
- 48. Structures Involved inAbsorption Structures Involved in Absorption of Nutrients of Nutrients Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Absorptive cells • Blood capillaries • Lacteals (specialized lymphatic capillaries) Figure 14.7b
- 49. Folds of theSmall Intestine Folds of the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Called circular folds or plicae circulares • Deep folds of the mucosa and submucosa • Do not disappear when filled with food • The submucosa has Peyer’s patches (collections of lymphatic tissue)
- 50. Digestion in theSmall Intestine Digestion in the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Enzymes from the brush border •Break double sugars into simple sugars •Complete some protein digestion • Pancreatic enzymes play the major digestive function •Help complete digestion of starch (pancreatic amylase) •Carry out about half of all protein digestion (trypsin, etc.)
- 51. Chemical Digestion inthe Small Chemical Digestion in the Small Intestine Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.6
- 52. Digestion in theSmall Intestine Digestion in the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Pancreatic enzymes play the major digestive function (continued) •Responsible for fat digestion (lipase) •Digest nucleic acids (nucleases) •Alkaline content neutralizes acidic chyme
- 53. Absorption in theSmall Intestine Absorption in the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Water is absorbed along the length of the small intestine • End products of digestion •Most substances are absorbed by active transport through cell membranes •Lipids are absorbed by diffusion • Substances are transported to the liver by the hepatic portal vein or lymph
- 54. Propulsion in theSmall Intestine Propulsion in the Small Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Peristalsis is the major means of moving food • Segmental movements •Mix chyme with digestive juices •Aid in propelling food
- 55. Digestive Secretions: (≈7 L/ Day From Tissues into Lumen) • Salivary glands • Pancreas • Water • Enzymes • Mucus • Ions: H+ , K+ , Na+ • HCO3 - , Cl- • Mass Balance (H2O)
- 56. Large Intestine Large Intestine Slide Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Larger in diameter, but shorter than the small intestine • Frames the internal abdomen
- 57. Large Intestine Large Intestine Slide Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.8
- 58. Cecum Cecum – – pocketat proximal end with Appendix Colon Colon Ascending colon - on right, between cecum and right colic flexure Transverse colon - horizontal portion Descending colon - left side, between left colic flexure and Sigmoid colon - S bend near terminal end Regions of Large Intestine Regions of Large Intestine Rectum Rectum – – terminal end is anal canal - ending at the anus - which has internal involuntary sphincter and external voluntary sphincter
- 59. 1. Mucosa -abundant goblet cells, stratified squamous epithelium near anal canal 2. No villi 3. Longitudinal muscle layer incomplete, forms three bands or taenia coli 4. Circular muscle - forms pockets or haustra between bands Histology of Large Intestine Histology of Large Intestine
- 60. Functions of theLarge Intestine Functions of the Large Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Absorption of water • Eliminates indigestible food from the body as feces • Does not participate in digestion of food • Goblet cells produce mucus to act as a lubricant
- 61. Structures of theLarge Intestine Structures of the Large Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Cecum – saclike first part of the large intestine • Appendix •Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) •Hangs from the cecum
- 62. Structures of theLarge Intestine Structures of the Large Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Colon •Ascending •Transverse •Descending •S-shaped sigmoidal • Rectum • Anus – external body opening
- 63. Food Breakdown andAbsorption in Food Breakdown and Absorption in the Large Intestine the Large Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • No digestive enzymes are produced • Resident bacteria digest remaining nutrients •Produce some vitamin K and B •Release gases • Water and vitamins K and B are absorbed • Remaining materials are eliminated via feces
- 64. Propulsion in theLarge Intestine Propulsion in the Large Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sluggish peristalsis • Mass movements •Slow, powerful movements •Occur three to four times per day • Presence of feces in the rectum causes a defecation reflex •Internal anal sphincter is relaxed •Defecation occurs with relaxation of the voluntary (external) anal sphincter
- 65. Saliva Saliva Slide Copyright © 2003Pearson Education, Inc. publishing as Benjamin Cummings • Mixture of mucus and serous fluids • Helps to form a food bolus • Contains salivary amylase to begin starch digestion • Dissolves chemicals so they can be tasted
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- 67. Enzymes in SmallIntestine
- 68. Pancreas Pancreas Slide • Produces awide spectrum of digestive enzymes that break down all categories of food • Enzymes are secreted into the duodenum • Alkaline fluid introduced with enzymes neutralizes acidic chyme • Endocrine products of pancreas (langerhans island) •Insulin •Glucagons •Somatostatin
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- 71. Composition and Functionof Pancreatic Juice • Examples include • Trypsinogen is activated to trypsin • Procarboxypeptidase is activated to carboxypeptidase • Active enzymes secreted • Amylase, lipases, and nucleases • These enzymes require ions or bile for optimal activity
- 72. • Retroperitoneal :compose ofhead, body and tail • Endocrine and exocrine gland • Common bile duct and major pancreatic duct lead to ampulla of vater then to second part of duodenum through sphincter of oddi Pancreas Pancreas
- 73. Liver Liver Slide Copyright © 2003Pearson Education, Inc. publishing as Benjamin Cummings • Largest gland in the body • Located on the right side of the body under the diaphragm • Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament • Connected to the gall bladder via the common hepatic duct
- 74. Liver On right underdiaphragm, largest organ made up of 4 lobes (left and right, caudate, and quadrate) Hilus (porta hepatis) – underside "entry" point Gall bladder Microscopic anatomy: Liver lobules and triads
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- 76. Visceral Surface ofthe Liver
- 77. Role of theLiver in Metabolism Role of the Liver in Metabolism Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Several roles in digestion • Detoxifies drugs and alcohol • Degrades hormones • Produce cholesterol, blood proteins (albumin and clotting proteins) • Plays a central role in metabolism
- 78. Bile Bile Slide Copyright © 2003Pearson Education, Inc. publishing as Benjamin Cummings • Produced by cells in the liver • Composition •Bile salts •Bile pigment (mostly bilirubin from the breakdown of hemoglobin) •Cholesterol •Phospholipids •Electrolytes
- 79. Gall Bladder Gall Bladder Slide Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sac found in hollow fossa of liver • Stores bile from the liver by way of the cystic duct • Bile is introduced into the duodenum in the presence of fatty food • Gallstones can cause blockages
- 80. Chemical Digestion inthe Small Chemical Digestion in the Small Intestine Intestine Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.6
- 81. Gallbladder • Stores andconcentrates bile to ten folds • Expels bile into duodenum – Bile emulsifies fats
- 82. Processes of theDigestive System Processes of the Digestive System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Ingestion – getting food into the mouth • Propulsion – moving foods from one region of the digestive system to another
- 83. Processes of theDigestive System Processes of the Digestive System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings •Peristalsis – alternating waves of contraction •Segmentation – moving materials back and forth to aid in mixing Figure 14.12
- 84. Processes of theDigestive System Processes of the Digestive System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Mechanical digestion •Mixing of food in the mouth by the tongue •Churning of food in the stomach •Segmentation in the small intestine
- 85. Processes of theDigestive System Processes of the Digestive System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Chemical Digestion •Enzymes break down food molecules into their building blocks •Each major food group uses different enzymes •Carbohydrates are broken to simple sugars •Proteins are broken to amino acids •Fats are broken to fatty acids and alcohols
- 86. Processes of theDigestive System Processes of the Digestive System Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Absorption •End products of digestion are absorbed in the blood or lymph •Food must enter mucosal cells and then into blood or lymph capillaries • Defecation •Elimination of indigestible substances as feces
- 87. Processes of theDigestive System Processes of the Digestive System Slide
- 88. Control of DigestiveActivity Control of Digestive Activity Slide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Mostly controlled by reflexes via the parasympathetic division • Chemical and mechanical receptors are located in organ walls that trigger reflexes
- 89. Nutrition Nutrition Slide • Nutrient –substance used by the body for growth, maintenance, and repair • Categories of nutrients •Carbohydrates: simple sugars, starches, fiber •Lipids: triglycerides, phospholipids, fatty acids •Proteins: amino acids •Vitamins •Mineral •Water