Final digestive system.


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Final digestive system.

  1. 1. (A Project of National Medical Centre Karachi) THE DIGESTIVE SYSTEM BY: SHAHZAD BASHIR LECTURER, NMC ION.Acknowledgment:Gail Jenkins, Christopher Kemnitz, Gerard Tortora 4/6/2013 Shahzad Bashir 1
  2. 2. Objectives. At the completion of this unit, learners will be able to: Define the digestive system and list its functions Identify the various organs of digestive system Describe the anatomy & physiology of digestive organs Discuss the role of accessory organs in digestion Discuss digestion of food with in ◦ Mouth ◦ Stomach ◦ Small intestines ◦ Large intestines Discuss the absorption of nutrients in the digestive system Discuss the process of defecation. 4/6/2013 Shahzad Bashir 2
  3. 3. Chapter Overview1 Gastrointestinal (GI) Tract2 Accessory Organs of the Head3 Swallowing4 Stomach5 Accessory Organs of the Abdomen6 Small Intestine7 Large Intestine8 Phases of Digestion9 Food Molecules10 Metabolism 4/6/2013 Shahzad Bashir 3
  4. 4. Essential TermsDigestion Process of mechanically or chemically breaking down foodAbsorption Passage of small molecules into blood and lymphDigestive system Organs which carry out process of digestion and absorptionMetabolism All the chemical reactions of the body 4/6/2013 Shahzad Bashir 4
  5. 5. Introduction.Digestive System. The digestive system contributes to homeostasis by breaking down food into forms that can be absorbed and used by body cells. 1. Composed of GI tract and accessory organs. 2. Breaks down ingested food for use by the body. 3. Digestion occurs by mechanical and chemical mechanisms. 4. Excretes waste products or feces through process of defecation. 5. The length of the GI tract is about 5–7 meters (16.5– 23 ft) in a living person. 6. It is longer in a cadaver (about 7–9meters or 23–29.5 ft) because loss of muscle tone. 4/6/2013 Shahzad Bashir 5
  6. 6. Concept.1Gastrointestinal (GI) Tract 4/6/2013 Shahzad Bashir 6
  7. 7. GI Tract / Alimentary Canal Continuous tube from mouth to anus Mouth Pharynx Esophagus Stomach Small intestine Large intestine 4/6/2013 Shahzad Bashir 7
  8. 8. Accessory Digestive OrgansProvide mechanical and chemicalmechanisms to aid digestionTeethTongueSalivary glandsLiverGallbladderPancreas 4/6/2013 Shahzad Bashir 8
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  10. 10. Functions of Digestive System1. Ingestion2. Secretion3. Mixing and propulsion • Motility4. Digestion • Mechanical and chemical5. Absorption6. Defecation 4/6/2013 Shahzad Bashir 10
  11. 11. Layers of GI Tract Same in all areas of GI tract From deep to superficial: Mucosa Sub mucosa Muscularis Serosa 4/6/2013 Shahzad Bashir 11
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  13. 13. Layers of GI Tract Mucosa ◦ Epithelium Type varies ◦ Lamina propria – areolar connective tissue MALT – mucus-associated lymphatic tissue ◦ Muscularis mucosae – smooth muscle Sub mucosa ◦ Areolar connective tissue ◦ Blood and lymphatic vessels ◦ Neurons – sub mucosal plexus 4/6/2013 Shahzad Bashir 13
  14. 14. Layers of GI Tract Muscularis ◦ Skeletal and smooth muscle ◦ Neurons – myenteric plexus Serosa ◦ Areolar and simple squamous epithelium ◦ Visceral peritoneum 4/6/2013 Shahzad Bashir 14
  15. 15. Peritoneum Parietal peritoneum Visceral peritoneum Peritoneal cavity Retroperitoneal 4/6/2013 Shahzad Bashir 15
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  20. 20. Folds of Peritoneum Greater omentum ◦ Adipose tissue Falciform ligament ◦ Liver to anterior abdominal wall Lesser omentum Mesentery ◦ Small intestine to posterior abdominal wall Mesocolon 4/6/2013 Shahzad Bashir 20
  21. 21. Neural Innervation of GI TractRegulated by autonomic nervous systemEnteric division◦ Myenteric plexus / plexus of Auerbach Major function is to regulate the movement of GIT◦ Submucosal plexus / plexus of Meissner Major function is the regulation of secretory function of GIT.Able to function independently from rest of nervoussystemLinked to CNS by extrinsic sympathetic andparasympathetic nervesSympathetic nerves decrease GI secretions & motilityParasympathetic nerves increase GI secretion andmotility 4/6/2013 Shahzad Bashir 21
  22. 22. Concept.2Accessory Organs of the Head 4/6/2013 Shahzad Bashir 22
  23. 23. ACCESSORY ORGANS ALIMENTARY CANAL Salivary glands Secrete saliva, which contains Mouth enzymes that initiate breakdown Mechanical breakdown of food; begins of carbohydrates chemical digestion of carbohydrates Pharynx Connects mouth with esophagus Esophagus Peristalsis pushes food to stomach Stomach Liver Secretes acid and enzymes; mixes food Produces bile, which with secretions to begin enzymatic emulsifies fat digestion of proteinsGallbladderStores bile and introduces it Small intestineinto small intestine Mixes food with bile and pancreatic juice; final enzymatic breakdown of food Pancreas molecules; main site of nutrient absorption Produces and secretes pancreatic juice, containing digestive enzymes and bicarbonate ions, into small Large intestine intestine Absorbs water and electrolytes to form feces Rectum Regulates elimination of feces 4/6/2013 Anus Shahzad Bashir 23
  24. 24. Mouth Parts of Digestive System Mouth formed by several parts: Cheeks Lips / labia Labial frenulum Orbicularis Vestibule Oral cavity proper Fauces Hard and soft palate Uvula Palatoglossal and palatopharyngeal arch 4/6/2013 Shahzad Bashir 24
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  26. 26. Tongue Skeletal muscle and mucous membrane Helps form floor of oral cavity Extrinsic muscles: Hyoglossus, genioglossus,& Styloglossus muscles. Intrinsic muscles: Longutudinalis superior, Inferior, Transversus linguae, Verticalis linguae. Lingual frenulum Papillae ◦ Fungiform ◦ Filiform ◦ Circumvallate ◦ Foliate Lingual glands ◦ Lingual lipase 4/6/2013 Shahzad Bashir 26
  27. 27. Tongue• The tongue is a Epiglottisthick, muscular Lingual tonsilsorgan that Rootoccupies the floor Palatine tonsilof the mouth andnearly fills the Bodyoral cavity when Papillaethe mouth isclosed 4/6/2013 Shahzad Bashir 27
  28. 28. Salivary Glands Release saliva to oral cavity 3 pairs of salivary glands Parotid: ◦ Largest salivary gland, weight about 20- 30 gram in adult. Open secretion through Stensen’s duct(35 to 40mm long). Submandibular: ◦ Weight about 8-10 gram, Secretion through Wharton’s duct (40mm long) Sublingual: ◦ Smallest gland, weight about 2-3g. Saliva open into 5 -15 small ducts called ducts of Ravinus. Largest duct is “Bartholin’s duct”. 4/6/2013 Shahzad Bashir 28
  29. 29. Composition of Saliva Volume: 1000-1500ml is secreted/day. About 1ml/minute. pH of saliva is slightly acidic 6.35 to 6.85. 99.5 % water 0.5% other solutes ◦ Ions ◦ Mucus ◦ Immunoglobulin A ◦ Enzymes Salivation controlled by autonomic nervous system Stimulated by various mechanisms 4/6/2013 Shahzad Bashir 29
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  31. 31. Teeth External regions 1. Crown 2. Root 3. Neck Internal components 1. Enamel 2. Dentin: Majority of teeth. Calcified connective tissue that gives tooth is basic shape and rigidity. Cementum 3. Pulp cavity PulpRoot canals Apical foramen 4/6/2013 Shahzad Bashir 31
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  33. 33. TeethDentitionsDeciduous teeth – first setPermanent teeth – secondaryCarry out mechanical digestion by masticationCreates bolusSalivary amylaseBreakdown starchLingual lipaseBreakdown triglycerides 4/6/2013 Shahzad Bashir 33
  34. 34. Incisors Canine (cuspid) Premolars (bicuspids) Molars Molars Premolars (bicuspids) Canine (cuspid) (a) Incisors Second premolars Central Lateral Canines First incisors incisors premolars (b)4/6/2013 ShahzadNick Koudis/Getty Images b: © Bashir 34
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  37. 37. Concept.3Swallowing 4/6/2013 Shahzad Bashir 37
  38. 38. PharynxComposed of skeletal muscleLined by mucous membraneNasopharynxOropharynxLaryngopharynx 4/6/2013 Shahzad Bashir 38
  39. 39. EsophagusCollapsible muscular tube through esophagealhiatus of diaphragm(25cm long)Mucosa◦ Submucosa contains areolar connective tissueMuscularis◦ Skeletal muscle◦ Upper and lower esophageal sphincterAdventitia◦ Attaches esophagus to nearby structuresSecrets mucus and transports food 4/6/2013 Shahzad Bashir 39
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  41. 41. DeglutitionDefinition:The act or process of swallowing.Stages of swallowingVoluntary◦ Mouth to oropharynxPharyngeal◦ Deglutition center in medulla oblongata and pons◦ Closing of epiglottis◦ InvoluntaryEsophageal◦ Involuntary◦ Peristaltic contractions 4/6/2013 Shahzad Bashir 41
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  45. 45. Concept.4Stomach 4/6/2013 Shahzad Bashir 45
  46. 46. Stomach The stomach is a J-shaped hollow muscular organ situated on the left side in the abdominal cavity,& in Epigastric, Umbilical and left hypochondriac region of abdomen, about 25-30 centimeters long. Serves as mixing chamber and storage area for ingested food When empty, its volume is 50ml & normally it can expand to accommodate 1 to 1.5 liters of solids & liquids. However it is also capable of expanding still further upto 4 liters. Rugae allow for increased volume. The food is stored for a long period, i-e. for 3 to 4 hours & emptied into the intestine slowly. 4/6/2013 Shahzad Bashir 46
  47. 47. Stomach. Total secretion of stomach per day is 2000-3000ml. 4 main regions1. Cardia2. Fundus3. Body4. Pylorus ◦ Pyloric antrum and canal ◦ Pyloric sphincter ◦ Lesser and greater curvatures 4/6/2013 Shahzad Bashir 47
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  49. 49. Stomach Histology1. Mucosa ◦ Surface mucous cells ◦ Lamina propria ◦ Muscularis mucosae ◦ Gastric glands and pits ◦ Parietal cells ◦ Chief cells ◦ G cells2. Submucosa – areolar connective tissue3. Muscularis ◦ 3 layers of smooth muscle4. Serosa 4/6/2013 Shahzad Bashir 49
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  53. 53. Mechanical and Chemical Digestion Mixing waves caused by peristaltic movement Chyme released in process of gastric emptying Proton pumps bring H+ into the lumen Carbonic anhydrase forms carbonic acid to provide H+ and bicarbonate ions (HCO3-) 4/6/2013 Shahzad Bashir 53
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  55. 55. Mechanical and Chemical Digestion Chemical digestion stimulated by nervous system Parasympathetic neurons release acetylcholine ◦ Works with gastrin ◦ HCl released in presence of histamine Pepsin begins digestion of proteins ◦ Stomach protected by alkaline mucus secretion Gastric lipase digests triglycerides Few molecules absorbed by stomach ◦ Water, ions, short-chain fatty acids, alcohol 4/6/2013 Shahzad Bashir 55
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  58. 58. Regulation of Gastric Secretions Release into 1 Parasympathetic bloodstream preganglionic nerve fiber (in Stimulation vagus nerve) 4 Gastrin stimulates gastric glands to release more gastric juice 2 Parasympathetic postganglionic impulses stimulate the release of Bloodstream gastric juice from 3 Impulses gastric glands stimulate the release of gastrin 4/6/2013 Shahzad Bashir 58
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  60. 60. Mixing and Emptying Actions Stomach Food entering Duodenum Pyloric sphincter Chyme Pyloric sphincter contracted relaxed(a) (b) (c) 4/6/2013 Shahzad Bashir 60
  61. 61. 4 Nerve impulses inhibit peristalsis in stomach wall From CNS Vagus nerve To CNS1 Duodenum fills with chyme 3 Sensory nerve impulses travel to central2 Sensory stretch nervous system receptors are stimulated 4/6/2013 Shahzad Bashir 61
  62. 62. Concept.5Accessory Organs ofthe Abdomen 4/6/2013 Shahzad Bashir 62
  63. 63. PancreasThe pancreas (pan- all; -creas flesh), aretroperitoneal gland that is about 12–15 cm(5–6 in.) long and 2.5 cm (1 in.) thick, liesposterior to the greater curvature of thestomach. Produces secretions to aid digestionHeadBodyTailPancreatic duct /duct of Wirsung◦ Hepatopancreatic ampulla◦ Sphincter of the heatopancreatic ampulla (sphincter of (Oddi) Regulates passage of pancreatic juice and bileAccessory duct (duct of Santorini) 4/6/2013 Shahzad Bashir 63
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  67. 67. Histology of Pancreas Glandular epithelial cells ◦ 99% exocrine clusters ◦ Secrete pancreatic juice Fluid and enzymes Pancreatic islets (islets of Langerhans) ◦ 1% endocrine cells ◦ Hormones Glucagon(Secrete by Alpha cell) Insulin(Secrete by Beta cell) Somatostatin (Secrete by Delta cell) ◦ Pancreatic polypeptide (Secrete by F cell) 4/6/2013 Shahzad Bashir 67
  68. 68. Pancreatic Juice 1200-1500 mL/day pH 7.1-8.2 Water Salts Sodium bicarbonate Enzymes ◦ Pancreatic amylase ◦ Trypsin Entereokinase ◦ Chymotrypsin ◦ Carboxypeptidase ◦ Elastase ◦ Pancreatic lipase ◦ Ribonuclease and deoxyribonuclease 4/6/2013 Shahzad Bashir 68
  69. 69. Regulation of Pancreatic Secretion Acidic chyme 1 enters duodenum 4 Pancreatic juice rich in bicarbonate ions passes down pancreatic ducts to the duodenum 5 Bicarbonate ions neutralize acidic chyme 3 Secretin stimulates pancreas to secrete bicarbonate ions 2 Intestinal mucosa releases secretin into bloodstream Bloodstream Hormonal signals released into bloodstream 4/6/2013 Shahzad Bashir Stimulation of effector organ 69
  70. 70. Liver and GallbladderLiver is the heaviest gland of the bodylocated in abdominal cavity, right, lefthypochondriac and part of the epigastricregions immediately beneath thediaphragm.Largest gland at 1.4 kg (~3 lb)GallbladderClosely associated with liver 4/6/2013 Shahzad Bashir 70
  71. 71. Anatomy of LiverRight and left lobe separated byfalciform ligamentQuadrate lobeCaudate lobeRound ligament (ligamentum teres)◦ Remnant of umbilical veinCoronary ligaments 4/6/2013 Shahzad Bashir 71
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  73. 73. Liver Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Inferior vena cava Gallbladder Quadrate lobeCoronary ligament Right lobe Left lobe Cystic duct Falciform ligament Hepatic duct Hepatic artery Hepatic portalRight lobe vein Left lobe Round ligament Bile duct Gallbladder Inferior vena cava Caudate lobe (a) (b) 4/6/2013 Shahzad Bashir 73
  74. 74. Histology of Liver Lobule ◦ Hepatocytes radiating from central vein ◦ Sinusoids Reticuloendothelial (Kupffer) cells ◦ Stationary phagocytes 4/6/2013 Shahzad Bashir 74
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  79. 79. Bile duct Bile canaliculi Bile ductule Kupffer cell Hepatic cellsBranch Branch Hepatic Central veinof hepatic of hepatic sinusoids (blood flowportal vein artery out of liver) Blood flow into liver 4/6/2013 Shahzad Bashir 79
  80. 80. Bile Duct SystemBile secreted by hepatocytesBile canaliculiBile ductsRight and left hepatic ductsCommon hepatic ductCommon bile ductGallbladder for temporary storage ofbileCystic duct 4/6/2013 Shahzad Bashir 80
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  82. 82. Blood Supply of Liver Hepatic artery provides oxygenated blood Hepatic portal vein provides deoxygenated blood ◦ Nutrients, drugs, toxins, microbes Hepatic artery and vein carry blood to sinusoids ◦ Substances exchanged by hepatocytes ◦ Blood drains to central vein and eventually hepatic vein Portal triad ◦ Hepatic portal vein ◦ Hepatic artery ◦ Bile duct 4/6/2013 Shahzad Bashir 82
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  84. 84. Regulation of Bile Release Cystic duct Common hepatic duct Gallbladder 3 CCK stimulates muscular layer of gallbladder wall to contract Bile duct 1 Chyme with 4 Bile passes down the cystic duct and bile duct to duodenum fat enters duodenum 5 Hepatopancreatic sphincter relaxes and bile enters duodenum Pancreatic duct Cells from the 2 intestinal mucosa secrete the hormone cholecystokinin (CCK) into the bloodstream Duodenum Hormonal signals released into bloodstream Bloodstream Stimulation of effector organ 4/6/2013 Shahzad Bashir 84
  85. 85. Bile800-1000 mL/daypH 7.6 – 8.6WaterBile acidsBile salts◦ EmulsificationCholesterolLecithinBile pigments◦ Bilirubin Stercobilin 4/6/2013 Shahzad Bashir 85
  86. 86. Liver FunctionsMetabolism of:◦ Carbohydrates◦ Lipids◦ ProteinsProcess drugs and hormonesExcrete bilirubinSynthesize bile saltsStorage◦ Glycogen◦ Vitamins◦ MineralsPhagocytosisActivate Vitamin D 4/6/2013 Shahzad Bashir 86
  87. 87. Gallbladder 4/6/2013 Shahzad Bashir 87
  88. 88. Concept.6Small Intestine 4/6/2013 Shahzad Bashir 88
  89. 89. Small IntestineMost digestion and absorption ofnutrients occur in a long tube called thesmall intestine.2.5 cm (1 in.) in diameter.3 m (10 ft) its length (living)6.5 m (21 ft) without muscle tone (afterdeath).DuodenumJejunumIleum 4/6/2013 Shahzad Bashir 89
  90. 90. Duodenum The shortest region, is retroperitoneal. It starts at the pyloric sphincter of the stomach and extends about 25 cm (10 in.) until it merges with the jejunum. Duodenum means “12”. It is so named because it is about as long as the width of 12 fingers. 4/6/2013 Shahzad Bashir 90
  91. 91. Jejunum. The jejunum is about 1 m (3 ft) long and extends to the ileum. Jejunum means “empty,” which is how it is found at death. 4/6/2013 Shahzad Bashir 91
  92. 92. Ileum The final and longest region of the small intestine, the ileum. (Ileum = twisted) Measures about 2 m (6 ft) and joins the large intestine at a smooth muscle sphincter called the ileocecal sphincter. (Peyer’s patches) are also present in the ileum. Ileocecal sphincter ◦ Connection to large intestine 4/6/2013 Shahzad Bashir 92
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  95. 95. Histology of Small IntestineMucosaCell types◦ Absorptive◦ Goblet◦ Endocrine◦ Paneth LysozymeIntestinal glands (crypts of Lieberkühn)◦ S cells Hormone secretin◦ CCK cells Hormone – cholecystokinin (CCK) 4/6/2013 Shahzad Bashir 95
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  97. 97. Microvilli Absorptive cell (absorbs nutrients)Blood Capillary Goblet cell (secretes Lacteal mucus) Enteroendocrine cell (secretes the hormones secretin, cholecystokinin, or GIP) Paneth cell (secretes lysozyme and is capable of phagocytosis) 4/6/2013 Shahzad Bashir 97
  98. 98. Structure of the Small Intestinal Wall Lumen Simple columnar epithelium Villus Lacteal IntestinalVillus gland Blood capillary network Goblet cells Intestinal gland © The McGraw-Hill Companies, Inc./Al Telser, photographer Arteriole Venule Lymph vessel 4/6/2013 Shahzad Bashir 98
  99. 99. (a) Plicae circularesVilli Submucosa Circular muscle Muscular Longitudinal muscle layer Serosa 99(b) 4/6/2013 Shahzad Bashir
  100. 100. Secretions of the Small Intestine• In addition to mucous-secreting goblet cells, there are manyspecialized mucous-secreting glands (Brunner’s glands) thatsecrete a thick, alkaline mucus in response to certain stimuli• Enzymes in the membranes of the microvilli include: • Peptidase – breaks down peptides into amino acids • Sucrase, maltase, lactase – break down disaccharides into monosaccharides • Lipase – breaks down fats into fatty acids and glycerol • Enterokinase – converts trypsinogen to trypsin • Somatostatin – hormone that inhibits acid secretion by stomach • Cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, and stimulates the gallbladder to release bile • Secretin – stimulates the pancreas to release bicarbonate ions in pancreatic juice 4/6/2013 Shahzad Bashir 100
  101. 101. Regulation ofSmall Intestinal Secretions• Regulation of small intestine secretion occursby: • Mucus secretion is stimulated by the presence of chyme in the small intestine • Distension of the intestinal wall activates nerve plexuses in the wall of the small intestine • Parasympathetic reflexes triggering the release of intestinal enzymes 4/6/2013 Shahzad Bashir 101
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  103. 103. Absorption of the Small Intestine• Villi increase the surface area for absorption• Small intestine absorption is so effective that very littlereaches the organ’s distal end, noting that: • Monosaccharides and amino acids absorb: • Through facilitated diffusion and active transport • Absorbed into blood • Large proteins are broken down and absorbed into villi • Fatty acids and glycerol absorb by: • Several steps involved as noted • Absorbed into lymph and blood • Electrolytes and water absorb: • Through diffusion, osmosis, and active transport • Absorbed into blood 4/6/2013 Shahzad Bashir 103
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  105. 105. O O O OH H H H H H H H Maltase H2O OHO OH HO OH HO OH Maltase Maltose + Water Glucose + Glucose Disaccharide Monosaccharides R O H R O H R O H O H Dipeptidase H N C C N C C OH H2O H N C C OH H N C C OH H H R H H Dipeptide + Water Dipeptidase Amino acid + Amino acid (from protein digestion) O H C17H35 C C HO C H H OH C17H35 COO C H O Lipase C17H35 COO C H 3H2O C17H35 C C HO C H H OH C17H35 COO C O H C17H35 C C HO C H OH H Fat + Water Lipase 4/6/2013 Shahzad Bashir + Fatty acids 105 Glycerol
  106. 106. Fats collect in clusters 3 encased in protein to form chylomicrons Nucleus Chylomicrons 4 leave epithelial cell2 Fatty acids are and enter lacteal used to synthesize fats in endoplasmic Chylomicrons reticulum 5 Lymph in lacteal transports chylomicrons away from intestine1 Fatty acids resulting from fat digestion enter epithelial cell Fatty acids Endoplasmic reticulum Lymph Epithelial cell Lacteal Lumen of intestine To blood 106 4/6/2013 Shahzad Bashir
  107. 107. Large Intestine.The large intestine is the terminal portionof the GI tract.The overall functions of the largeintestine are the completion ofabsorption, the production of certainvitamins, the formation of feces, and theexpulsion of feces from the body. 4/6/2013 Shahzad Bashir 107
  108. 108. Parts of the Large Intestine Muscular layer Mucous membrane Serous layer Transverse colon Hepatic flexure Splenic flexure Ascending colon Tenia coli Epiploic appendage Descending colon Ileum Ileocecal sphincter Orifice of appendix Haustra Cecum Appendix Rectum Sigmoid colon 4/6/2013canal Anal Shahzad Bashir 108
  109. 109. Anatomy of Large Intestine. The large intestine, which is about 1.5 m (5 ft) long and 6.5 cm (2.5 in.) in diameter. Extends from the ileum to the anus. Structurally, the four major regions of the large intestine are the cecum, colon, rectum, and anal canal. 4/6/2013 Shahzad Bashir 109
  110. 110. Anatomy of Large Intestine. Ileocecal sphincter (valve), which allows materials from the small intestine to pass into the large intestine. Hanging inferior to the ileocecal valve is the cecum, a small pouch about 6 cm (2.4 in.) long. Attached to the cecum is a twisted, coiled tube, measuring about 8 cm (3 in.) in length, called the appendix or vermiform appendix (vermiform worm- shaped; appendix = appendage). 4/6/2013 Shahzad Bashir 110
  112. 112. Anatomy of Large Intestine. The open end of the cecum merges with a long tube called the colon( food passage), which is divided into ascending, transverse, descending, and sigmoid portions. 4/6/2013 Shahzad Bashir 112
  113. 113. Functions of the Large Intestine1. Haustral churning, peristalsis, and mass peristalsis drive the contents of the colon into the rectum.2. Bacteria in the large intestine convert proteins to amino acids, break down amino acids, and produce some B vitamins and vitamin K.3. Absorbing some water, ions, and vitamins.4. Forming feces.5. Defecating (emptying the rectum). 4/6/2013 Shahzad Bashir 113
  114. 114. Feces• Feces is composed of materials not digested orabsorbed, and include: • Water • Electrolytes • Mucus • Bacteria • Bile pigments altered by bacteria provide the color• The pungent odor is produced by bacterialcompounds including: • Phenol • Hydrogen sulfide • Indole • Skatole • Ammonia 4/6/2013 Shahzad Bashir 114
  115. 115. Lifespan Changes• Changes to the digestive system are slow andslight, and eventually include: • Teeth may become sensitive • Gums may recede • Teeth may loosen, break or fall out • Heartburn may become more frequent • Constipation may become more frequent • Nutrient absorption decreases • Accessory organs age but typically not necessarily in ways that effect health 4/6/2013 Shahzad Bashir 115
  116. 116. REFERENCESTortora, G. J. & Grabowski, S.R. (2000).Principles of anatomy and physiology (12thed.). New York: John Wiley & sons Inc.Eline, N.M, Essential of human anatomy &physiology (9th ed.). New York: John Wiley& sons Inc. 4/6/2013 Shahzad Bashir 116
  117. 117. End of Chapter 4/6/2013 Shahzad Bashir 117