ANATOMY OF ESOPHAGUS WITH PHYSIOLOGY OF DEGLUTITION

ANATOMY EMBRYOLOGY OF ESOPHAGUS.
PHYSIOLOGY OF DEGLUTITION

1. OESOPHAGUS Susritha.k ,dpt of ent;ASRAMS

2. TABLE OF CONTENTS 1)DEVELOPMENT OF - PHARYNX - OESOPHAGUS & TRACHEA. 2)DEVELOPMENTAL ANAMOLIES. 3)ANATOMY OF OESOPHAGUS. 4)BLOOD SUPPLY 5)VENOUS & LYMPHATIC DRAINAGE. 6)NERVE SUPPLY. 7)PHYSIOLOGY OF DEGLUTION.

3. EMBRYOLOGY OF PHARYNX

4. Buccopharyngeal membrane separates stomodeum from fore gut. Cranio -caudally boundaries of foregut are: Ventrallystomodeum . developing heart. septum transversum . Dorsally notochord . dorsal aorta.

5. b/w the arches branchial clefts. Corresponding endodermal groovespharyngeal pouches. Each branchial arch extends to meet its fellow on the opposite side.

6. BRANCHIAL APPARATUS

7. Development of pharynx.

8. DEVELOPMENT OF OESOPHAGUS

9. 4 th wk of IULrespiratory diverticulum appears at ventral wall of foregut. Tracheo-oesophageal septum separates resp.diverticulum fromdorsal part of foregut. Thus results the formation of Oesophagus~dorsally Respiratory primordium~ventrally . At 1 st osophagus is short but later elongates with the descent of heart & lungs.

10. DEVELOPMENT OF TRACHEA BRONCHI AND LUNGS. During its separation from foregut,lung bud gets converted into a tubetrachea 2 lateral out pouchingsbronchial buds.

11. AT THE BEGENNING OF 5 TH WK EACH BUD ENLARGES TO FORM

12. DEVELOPMENT OF TRACHEA & BRONCHI

13. FORMATION OF SECONDARY BRONCHI

14. FIGURE SHOWING FORMATION OF TERTIARY BRONCHI

15. MATURATION OF LUNGS

16. CANALICULAR PERIOD TERMINAL SAC PERIOD

17. ALVEOLAR PERIOD

18. DEVELOPMENTAL ANAMOLIES OESOPHAGEAL ATRESIA/TRACHEO - OESOPHAGEAL FISTULA . Spontaneous posterior deviation of oesophago tracheal septum. Mechanical factor pushing dorsal wall of foregut anteriorly .

19. Most common common form  proximal part of oesophagus ends as blind sac distal partconnected to trachea just above its bifurcation.

20. OESOPHAGEAL ATRESIA//TR.OS FISTULA

21. TRACHEOSCOPY SHOWING OESOPHAGEAL FISTULA.

22. RADIOGRAPHICAL FEATURES OF TRACHEO OESOPHAGEAL FISTULA

23. ANATOMY OF OESOPHAGUS EXTENSION: lower border of cricoid at Vc6 level passes through diaphragm at V T10 levelends at V T11 near cardiac orifice. LENGTH:25cms. DIAMETRE:2.5-3cms.

24. Curvatures.

25. CONSTRICTIONS At cricopharyngeal sphincter 15cms from incisors. Where aortic arch crosses22-25cms from incisors. Where it is crossed by left bronchus27-28cms from incisors. Where it passes through diaphragm38-40cms from incisors.

26. Topographically, there are three distinct regions: cervical, thoracic, and abdominal. CERVICAL OESOPHAGUS: extends from the pharyngoesophageal junction to the suprasternal notch. about 4 to 5 cm long. At this level, the esophagus is bordered anteriorly by the trachea, posteriorly by the vertebral column, and laterally by the carotid sheaths and the thyroid gland.

27. THORACIC OESOPHAGUS: Extends from the suprasternal notch  diaphragmatic hiatus. Passes posterior to the trachea, the tracheal bifurcation, and the left main stem bronchus.

28. The esophagus lies posterior and to the right of the aortic arch at the T4 vertebral level. From the level of T8 until the diaphragmatic hiatus the esophagus lies anteriorly to the aorta

29. ABDOMINAL OESOPHAGUS: extends from the diaphragmatic hiatus  orifice of the cardia of the stomach. Forms a truncated cone, about 1 cm long.

30. Structurally, the esophageal wall is composed of four layers: > innermost mucosa, > submucosa , > muscularis propria , >adventitia. Unlike the remainder of the GI tract, the esophagus has no serosa . Lined by non keratinised stratifed squamous epithelium.

31. HISTOLOGY-OESOPHAGUS.

32. MUSCULATURE The muscular coat consists -external layer  longitudinal fibers -internal layer  circular fibers. The longitudinal fibers are arranged proximally in three fasciculi . -A ventral fasciculus -two lateral fasciculi that are continuous with muscle fibers of the pharynx.

33. LONGITUDINAL FIBRES: form a uniform layer that covers the outer surface of the esophagus. CIRCULAR FIBRES: provides the sequential peristaltic contraction that propels food toward the stomach. The circular fibers are continuous with the inferior constrictor muscle of the hypopharynx . They run transversely  in cranial & caudal regions. obliquely  body of the esophagus.

34. The internal muscular layer is thicker than the external muscular layer. Below the diaphragm, the internal circular muscle  thickens ,constituting the intrinsic component of LES. Muscular fibers in the cranial part  red and consist chiefly striated muscle. Intermediate part  mixed . Lower part  contains only smooth muscle.

35. RADIOLOGICAL VIEW OF OESOPHAGEAL MUCOSA.

36. Two high-pressure zones prevent the backflow of food: the upper and lower oesophageal sphincter. These functional zones are located at the upper and lower ends of the oesophagus .

37. UPPER OESOPHAGEAL SPHINCTER Between pharynx and the cervical oesophagus . Located at C5-C6 level. The UES is a musculocartilaginous structure. Composed of mainly three muscles: cricopharyngeus , thyropharyngeus,cranial cervical oesophagus .

38. The cricopharyngeus muscle is a striated muscle. produces maximum tension in the A.P direction and less tension in lateral direction. composed of a mixture of fast- and slow-twitch fibres . This muscle forms the main component of UES.

39. KILLIANS TRIANGLE OR LAIMERS TRIANGLE. Triangular area in the wall of pharynx b/w thyropharyngeus and cricopharyngeus muscles.

40. LOWER OESOPHAGEAL SPHINCTER The lower esophageal sphincter is a high-pressure zone located where the esophagus merges with the stomach. Mean pressure here is approx. 8mm Hg.

41. The LES is a functional unit composed of an intrinsic and an extrinsic component. INTRINSIC  oesophageal muscle fibers and is under neurohormonal influence EXTRINSIC  diaphragm muscle.

42. The endoscopic localization of the LES is different from the manometric localization. The endoscopic localization  determined by changes in the esophageal mucosal transition from nonstratified squamous esophageal epithelium to the gastric mucosa  “Z- line”or B ring. Functional location of LES is 3 cm distal to the Z-line.

43. LES-ENDOSCOPIC VIEW

44. Bulbous distension of distal oesophagus vestibule . It corresponds to manometrically defined LES.

45. ‘B’RING/Z-LINE

46. BLOOD SUPPLY The rich arterial supply of the esophagus is segmental . Branches of the inferior thyroid artery UES and cervical esophagus. Paired aortic esophageal arteries or terminal branches of bronchial arteries  thoracic esophagus. The left gastric artery and a branch of the left phrenic artery  LES and the most distal segment of the esophagus.

47. VENOUS DRAINAGE The venous supply is also segmental. From the dense submucosal plexus the venous blood drains into the superior vena cava. veins of proximal and distal esophagus  azygous system. Veins of mid oesophagus collaterals of left gastric vein.

48. LYMPHATICS The lymphatics from the proximal 1/3 rd  drain into the deep cervical LNs  subsequently into the thoracic duct. Middle 1/3 rd  into superior and posterior mediastinal nodes. Distal 1/3 rd  gastric and celiac lymph nodes.

49. NERVE SUPPLY Parasympathetic nerve supply  (SENSORY,MOTOR,SECRETOMOTOR) Upper ½rec.laryngeal nerve. Lower ½oesophageal plexus formed by the 2 vagus plexus. The sympathetic nerve supply (VASOMOTOR ) Upper ½by fibres from mid cervical ganglion. Lower ½ directly from upper four thoracic ganglia.

50. Esophageal sensory innervation is carried by the vagus nerve To the nodose ganglion Through the thalamus Terminates in the cortex.

51. The ganglia that lie between the longitudinal and the circular layers  myenteric or Auerbach's plexus. That lie in the submucosa form the submucous or Meissner's plexus. Auerbach's plexus  regulates contraction of the outer muscle layers. Meissner's plexus  regulates secretion and the peristaltic contractions of the muscularis mucosae .

52. PHYSIOLOGY OF DEGLUTITION DEFINITION: Deglutition is the process of propulsion of bolus of food from oral cavity into stomach.

53. ORAL PHASE: Voluntary ; under the control of cerebral cortex. Food bolus~on a depression in middle of tongue. Bolus held b/w tongue & ant.hard palate Ant. to post. tongue movement(1 sec) Movement of bolus into oropharynx .

54. ORAL PREPERATORY PHASE: processing of bolus to render it swallowable . ORAL PROPULSIVE PHASE: propelling of food from oral cavity into oropharynx .

55. PHARYNGEAL PHASE: Soft palate elevates closing the naso pharynx. Sup.constrictor contracts ; tongue base drives the bolus posteriorly . Respiration ceases. Larynx elevates. Epiglottis retroflexes & arytenoids adduct. Bolus propulsion.

56. Cricopharyngeus & inf.constrictor relaxes food into upper oesophagus . UESrelaxes in pharyngeal phase;closesafter passage of food.

57. OESOPHAGEAL PHASE:(8-20SECS) Comenses as soon as food passes cricopharyngeal sphincter. Peristaltic wave in response to distension of wall by bolus.

58. Circular muscles contract behind & relax infront of bolus. Followed by contraction of smooth muscle. LES relaxes & bolus moves into oesophagus

59. Oesophageal phase

60. Swallow reflex: complex neurological event involving participation of high cortical centres . tract of nucleus solitarius & nucleusambiguous . CNs 5,7,9,10 & 12.

61. PHASES OF DEGLUTITION

62. THEORY OF CONSTANT PROPORTION. THEORY OF INTEGRAL FUNCTION. THEORY OF NEGATIVE PRESSURE. THEORY OF ORAL EXPULSION. ~~****~~ THEORIES OF DEGLUTITION