The Digestive System


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Lecture on the anatomy of the Digestive Tract for BS Bio students.

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The Digestive System

  1. 1. The Digestive Apparatus Lectured by Bien Nillos, MD Anatomy Class BS Biology Reference: Gray’s Anatomy
  2. 2. Pre-lecture Quiz <ul><li>The most dilated part of the Gastrointestinal Tract </li></ul><ul><li>- 3. Give two examples of accessory organs in the G.I. Tract </li></ul><ul><li>4. – 6. Three parts of the small intestine </li></ul><ul><li>7. – 9. Three salivary glands </li></ul><ul><li>10. – 11. 2 openings of the stomach </li></ul><ul><li>12. – part of the large intestine where the appendix is attached </li></ul><ul><li>13. – 15. 3 major glands of the stomach </li></ul>
  3. 3. The Digestive System: 2 parts <ul><li>Alimentary Canal – digestive tube </li></ul><ul><ul><li>9 meters long, from mouth to anus </li></ul></ul><ul><ul><li>lined throughout its entire extent by mucous membrane. </li></ul></ul><ul><ul><li>Mouth  pharynx  esophagus  stomach  small intestine  large intestine  anus </li></ul></ul><ul><li>Accessory Organs – </li></ul><ul><ul><li>Teeth; salivary glands (3 pairs); liver; pancreas; gallbladder </li></ul></ul>
  4. 5. The Mouth <ul><li>consists of two parts: </li></ul><ul><li>the vestibule - an outer, smaller portion </li></ul><ul><ul><li>slit-like space, bounded externally by the lips and cheeks; internally by the gums and teeth </li></ul></ul><ul><ul><li>receives the secretion from the parotid salivary glands </li></ul></ul><ul><li>the  mouth cavity proper - an inner, larger part </li></ul><ul><ul><li>bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the pharynx by a constricted aperture termed the  isthmus faucium.   </li></ul></ul><ul><ul><li>roofed in by the hard and soft palates, </li></ul></ul><ul><ul><li>while the greater part of the floor is formed by the tongue </li></ul></ul><ul><ul><li>receives the secretion from the submaxillary and sublingual salivary glands. </li></ul></ul>
  5. 6. <ul><li>The  Lips  ( labia oris ) are formed externally of integument and internally of mucous membrane, between which are found the Orbicularis oris muscle , the labial vessels, some nerves, areolar tissue, and fat, and numerous small labial glands. </li></ul><ul><li>  The  Cheeks  ( buccæ ) form the sides of the face, and are continuous in front with the lips. They are composed externally of integument; internally of mucous membrane; and between the two of a muscular stratum, besides a large quantity of fat, areolar tissue, vessels, nerves, and buccal glands. </li></ul>
  6. 7. <ul><li>The  Gums  are composed of dense fibrous tissue, closely connected to the periosteum of the alveolar processes, and surrounding the necks of the teeth. They are covered by smooth and vascular mucous membrane, which is remarkable for its limited sensibility.  </li></ul>
  7. 8. Palate <ul><li>The  Hard Palate  is bounded in front and at the sides by the alveolar arches and gums; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous membrane of the mouth, which are intimately adherent. </li></ul><ul><li>The  Soft Palate  is a movable fold, suspended from the posterior border of the hard palate, and forming an incomplete septum between the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibers, an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands. </li></ul>
  8. 10. Soft Palate <ul><li>Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the pharynx. </li></ul><ul><li>Its lower border is free . Its lower portion, which hangs like a curtain between the mouth and pharynx is termed the palatine velum . </li></ul><ul><li>Hanging from the middle of its lower border is a small, conical, pendulous process, the palatine uvula </li></ul>
  9. 11. The Teeth (dentes) <ul><li>Deciduous vs. Permanent set </li></ul><ul><li>The  deciduous teeth  are twenty in number: 4 incisors, 2 canines, and 4 molars, in each jaw. </li></ul><ul><li>The  permanent teeth  are thirty-two in number: 4 incisors, 2 canines, 4 premolars, and 6 molars, in each jaw. </li></ul>
  10. 12. <ul><li>Each tooth consists of three portions: the  crown,  projecting above the gum; the  root,  imbedded in the alveolus; and the  neck,  the constricted portion between the crown and root. </li></ul>
  11. 13. <ul><li>the  pulp cavity,  and contains the  dental pulp,  a loose connective tissue richly supplied with vessels and nerves, which enter the cavity through the small aperture at the point of each root. </li></ul>
  12. 14. <ul><li>The solid portion of the tooth consists of: </li></ul><ul><li>the  ivory  or  dentin,  which forms the bulk of the tooth </li></ul><ul><li>the  enamel,  which covers the exposed part of the crown; </li></ul><ul><li>a thin layer of bone, the  cement  or  crusta petrosa,  which is disposed on the surface of the root. </li></ul>
  13. 15. The Tongue <ul><li>The tongue is the principal organ of the sense of taste, and an important organ of speech; it also assists in the mastication and deglutition of the food. It is situated in the floor of the mouth, within the curve of the body of the mandible. </li></ul>
  14. 16. <ul><li>Its  Root  is directed backward, and connected with the hyoid bone by the Hyoglossi and Genioglossi muscles and the hyoglossal membrane </li></ul><ul><li>Its  Apex, thin and narrow, is directed forward against the lingual surfaces of the lower incisor teeth. </li></ul>
  15. 17. <ul><li>The  Papillæ of the Tongue  are projections of the corium. They are thickly distributed over the anterior two-thirds of its dorsum, giving to this surface its characteristic roughness. </li></ul>
  16. 18. Muscles of the Tongue <ul><li>Extrinsic Muscles: Genioglossus, Hyoglossus, Chondroglossus, Styloglossus, Glossopalatinus. </li></ul><ul><li>Intrinsic Muscles: Longitudinalis superior, Transversus, Longitudinalis inferior, Verticalis. </li></ul>
  17. 19. <ul><li>Blood Supply : lingual branch of the external carotid </li></ul><ul><li>Venous Drainage : internal jugular vein </li></ul><ul><li>Motor Nerve Supply : Hypoglossal Nerve </li></ul><ul><li>Sensory Nerve Supply : lingual branch of the Mandibular Nerve, chorda tympani branch of the Facial Nerve, lingual branch of the Glossopharyngeal Nerve, superior laryngeal nerve </li></ul>
  18. 20. Salivary Glands <ul><li>Parotid – largest of the three </li></ul><ul><ul><li>lies upon the side of the face, immediately below and in front of the external ear </li></ul></ul><ul><ul><li>Stensen’s Duct: opens upon the oral surface of the cheek by a small orifice, opposite the second upper molar tooth </li></ul></ul><ul><li>Submaxillary - about the size of a walnut </li></ul><ul><ul><li>situated in the submaxillary triangle </li></ul></ul><ul><ul><li>Wharton’s Duct: opens by a narrow orifice on the summit of a small papilla, at the side of the frenulum linguæ </li></ul></ul><ul><li>Sublingual - the smallest of the three glands </li></ul><ul><ul><li>situated beneath the mucous membrane of the floor of the mouth, at the side of the frenulum linguæ </li></ul></ul><ul><ul><li>excretory ducts are from eight to twenty in number.  (Duct of Rivinus, duct of Bartholin) </li></ul></ul>
  19. 22. The Pharynx <ul><li>placed behind the nasal cavities, mouth, and larynx. </li></ul><ul><li>It is a musculomembranous tube, somewhat conical in form </li></ul><ul><li>greatest breadth is immediately below the base of the skull, where it projects on either side, behind the pharyngeal ostium of the auditory tube, as the  pharyngeal recess  ( fossa of Rosenmüller ) </li></ul>
  20. 24. The Esophagus <ul><li>a muscular canal, about 23 to 25 cm. long, extending from the pharynx to the stomach. </li></ul><ul><li>It begins in the neck at the lower border of the cricoid cartilage, opposite the sixth cervical vertebra </li></ul><ul><li>descends along the front of the vertebral column, through the superior and posterior mediastina </li></ul><ul><li>passes through the diaphragm </li></ul><ul><li>ends at the cardiac orifice of the stomach, opposite the eleventh thoracic vertebra </li></ul>
  21. 25. <ul><li>The esophagus has four coats: </li></ul><ul><li>an  external  or  fibrous, </li></ul><ul><li>Muscular </li></ul><ul><li>A submucous  or  areolar </li></ul><ul><li>an  internal  or  mucous coat. </li></ul>
  22. 26. <ul><li>Blood Supply : inferior thyroid branch of the thyrocervical trunk, from the descending thoracic aorta, from the left gastric branch of the celiac artery, and from the left inferior phrenic of the abdominal aorta </li></ul><ul><li>Nerve supply : Vagus nerves, sympathetic trunks </li></ul>
  23. 27. The Stomach <ul><li>the most dilated part of the digestive tube, </li></ul><ul><li>situated between the end of the esophagus and the beginning of the small intestine. </li></ul><ul><li>It lies in the epigastric, umbilical, and left hypochondriac regions of the abdomen </li></ul><ul><li>occupies a recess bounded by the upper abdominal viscera and completed in front and on the left side by the anterior abdominal wall and the diaphragm. </li></ul>
  24. 29. Rule of 2’s <ul><li>2 openings: cardiac orifice vs. pyloric orifice </li></ul><ul><li>2 borders/curvatures: lesser vs. greater </li></ul><ul><li>2 surfaces: Antero-superior vs. Postero-inferior </li></ul>
  25. 30. Component Parts of the Stomach
  26. 31. Walls of the Stomach <ul><li>Serous – tunica serosa </li></ul><ul><ul><li>Derived from the peritoneum </li></ul></ul><ul><li>Muscular – tunica muscularis </li></ul><ul><ul><li>Longitudinal, circular and oblique muscle fibers </li></ul></ul><ul><li>Areolar – tela submucosa </li></ul><ul><ul><li>Loose areolar tissue </li></ul></ul><ul><li>Mucous – tunica mucosa </li></ul><ul><ul><li>During the contracted state of the organ it is thrown into numerous plaits or rugae </li></ul></ul>
  27. 33. Glands of the Stomach <ul><li>( a )  pyloric   </li></ul><ul><li>( b )  cardiac </li></ul><ul><li>( c ) fundus  or  oxyntic glands </li></ul>
  28. 34. <ul><li>Blood Supply:  the left gastric, the right gastric and right gastroepiploic branches of the hepatic artery , and the left gastroepiploic and short gastric branches of the splenic artery </li></ul><ul><li>Nerve supply: Vagus nerves </li></ul>
  29. 35. The Small Intestines <ul><li>a convoluted tube, extending from the pylorus to the colic valve, where it ends in the large intestine. </li></ul><ul><li>It is about 7 meters long and gradually diminishes in size from its commencement to its termination </li></ul><ul><li>three portions: the duodenum ,  the  jejunum ,  and the  ileum . </li></ul>
  30. 37. Duodenum <ul><li>the shortest, the widest, and the most fixed part of the small intestine, and has no mesentery, being only partially covered by peritoneum </li></ul><ul><li>Its course presents a remarkable curve, somewhat of the shape of an imperfect circle, so that its termination is not far removed from its starting-point. </li></ul>
  31. 38. <ul><li>may be divided into four portions:  superior, descending, horizontal,  and  ascending. </li></ul>
  32. 39. <ul><li>Blood Supply: right gastric and superior pancreaticoduodenal branches of the hepatic artery , and the inferior pancreaticoduodenal branch of the superior mesenteric artery </li></ul>
  33. 40. Jejunum and Ileum <ul><li>The  Jejunum  is wider, its diameter being about 4 cm., and is thicker, more vascular, and of a deeper color than the ileum, so that a given length weighs more </li></ul><ul><li>The aggregated lymph nodules are almost absent in the upper part of the jejunum, and in the lower part are less frequently found than in the ileum, and are smaller and tend to assume a circular form </li></ul>
  34. 41. <ul><li>The  Ileum  is narrow, its diameter being 3.75 cm., and its coats thinner and less vascular than those of the jejunum. </li></ul><ul><li>It possesses but few circular folds, and they are small and disappear entirely toward its lower end, but aggregated lymph nodules ( Peyer’s patches ) are larger and more numerous. </li></ul>
  35. 42. The Wall of the Small Intestine <ul><li>four coats:  </li></ul><ul><li>Serous coat – tunica serosa </li></ul><ul><ul><li>derived from the peritoneum </li></ul></ul><ul><li>Muscular coat – tunica muscularis </li></ul><ul><ul><li>two layers of unstriped fibers: an external, longitudinal, and an internal, circular layer.  </li></ul></ul><ul><li>Areolar coat – tela submucosa </li></ul><ul><ul><li>containing bloodvessels, lymphatics, and nerves. </li></ul></ul><ul><ul><li>It is the strongest layer of the intestine </li></ul></ul><ul><li>Mucous coat – tunica mucosa </li></ul><ul><ul><li>thick and highly vascular at the upper part of the small intestine, but somewhat paler and thinner below </li></ul></ul>
  36. 43. Glands <ul><li>crypts of Lieberkühn –  found in considerable numbers over every part of the mucous membrane of the small intestine </li></ul><ul><li>Brunner’s glands – limited to the duodenum and are found in the submucous areolar tissue </li></ul><ul><li>Solitary glands - are found scattered throughout the mucous membrane of the small intestine, but are most numerous in the lower part of the ileum </li></ul>
  37. 44. <ul><li>Blood supply of Jejunum and Ileum: superior mesenteric artery </li></ul><ul><li>Nerve supply: </li></ul><ul><ul><li>myenteric plexus  ( Auerbach’s plexus ) of nerves and ganglia situated between the circular and longitudinal muscular fibers from which the nervous branches are distributed to the muscular coats of the intestine. </li></ul></ul><ul><ul><li>From this a secondary plexus, the  plexus of the submucosa  ( Meissner’s plexus ) is derived, and is formed by branches which have perforated the circular muscular fibers . </li></ul></ul>
  38. 45. The Large Intestine <ul><li>extends from the end of the ileum to the anus. It is about 1.5 meters long, being one-fifth of the whole extent of the intestinal canal. Its caliber is largest at its commencement at the cecum, and gradually diminishes as far as the rectum, where there is a dilatation of considerable size just above the anal canal.  </li></ul>
  39. 48. End of Part One of Digestive Tract “ A hungry stomach cannot hear.”  Jean de La Fontaine 
  40. 49. FINAL (MAJOR MAJOR) PROJECT <ul><li>CLASS VIDEO </li></ul><ul><ul><li>Of any genre: music video, telenovela, commercial, talk show, game show, reality show, indie-film…etc…. </li></ul></ul><ul><ul><li>Must feature and mention the keywords for each featured Organ/Organ system </li></ul></ul><ul><ul><li>Length of video must not exceed 7 minutes </li></ul></ul><ul><ul><li>Language used must be English and/or Filipino only </li></ul></ul><ul><ul><li>No lewdness, use of foul language, etc. </li></ul></ul><ul><ul><li>To be graded according to the ff. criteria: </li></ul></ul>
  41. 50. <ul><li>Accuracy and Ability to incorporate keywords into the presentation – 30% </li></ul><ul><li>Creativity and Originality – 20% </li></ul><ul><li>Informative and Educational – 30% </li></ul><ul><li>Entertainment Value – 20% </li></ul><ul><li>Total Score: 100% </li></ul>
  42. 51. 5 GROUPS (should not exceed 7 members) <ul><li>GROUP ONE: LIVER – keywords: bile, hepatic cells, liver, falciform ligament, hepatic artery, portal vein, Glisson’s capsule </li></ul><ul><li>GROUP TWO: PANCREAS – keywords: head, tail, uncinate, neck, duct of Wirsung, duct of Santorini, islet of Langerhans, </li></ul>
  43. 52. <ul><li>GROUP THREE – KIDNEYS: keywords: nephron, juxtaglomerular apparatus, Loop of Henle, collecting ducts, renal artery, Gerota’s fascia, adrenal glands </li></ul><ul><li>GROUP FOUR – URINARY BLADDER: keywords: ureters, urethra, trigone, fundus, detrusor, sphincter, distended bladder </li></ul>
  44. 53. <ul><li>GROUP FIVE – SPLEEN: keywords: ductless gland, phrenicolienal ligament , splenic pulp, splenic artery, Malpighian bodies, gastrolienal ligament , accessory spleen </li></ul>
  45. 54. <ul><li>DEADLINE: OCTOBER 1, 2010 </li></ul><ul><li>To be submitted in MPEG format…in a CD. </li></ul><ul><li>JUDGES: teachers, doctors, etc. </li></ul><ul><li>Average scores will be the scores for the project. </li></ul><ul><li>Should the First Place exceed 95% average score, First Place may be exempted from taking the FINAL EXAM. </li></ul><ul><li>REMINDER: project need not be costly. Imagination and resourcefulness is the key. Remember: imagination is more important than knowledge (Siling ni Einstein) </li></ul>