Anatomy of oesophagus

Anatomy of oesophagus

1. Anatomy of oesophagus Dr.Saheena.n

2. introduction The immediate continuation of the pharynx and a conduit for food and fluids into the stomach It is Collapsed at rest Flat in upper 2/3 & rounded in lower 1/3 It is 25 cm in length Commences from the lower border of the cricoid cartilage .(C6). Then it descends along the front of the spine, through the posterior mediastinum, passes through the Diaphragm, and, enters into the abdomen terminates at the cardiac orifice of the stomach, opposite to T11 vertebra.

3. development  Comes from two sources of the primitive gut. The cranial portion is derived from the pharyngeal gut or pharynx and the caudal part from the pregastric segment of the foregut Primitive foregut forms at 4th week of gestation by a longitudinal folding and incorporation of the dorsal part of the yolk sac into the embryo Then appears a small diverticulum on the ventral wall of the foregut at the junction with the pharyngeal gut   at the level of the fourth pharyngeal pouches “ Respiratory or tracheobronchial diverticulum”

4. This tracheobronchial diverticulum separates from the developing oesophagus by the formation of the oesophagotracheal septum The developing oesophagus is a short tube which extends from the tracheobronchial diverticulum to the future stomach

5. The endoderm forms the mucosal epithelium and associated ducts and glands. The mesoderm forms the lamina propria, muscularis mucosa, and muscular coat T he branchial arches forming the striated muscle and the visceral splanchnic mesoderm the smooth muscle coat. Arterial and venous supply of the esophagus is segmental. The cranial arteries are derived from the branchial arches and caudal ones from branches of the aorta With the unfolding and lengthening of the embryo, the esophagus also lengthens

6. Upper two thirds is striated and innervated by vagus and lower third is smooth muscle and innervated by splanchnic plexus. Circular muscle coat is formed by the surrounding mesenchyme at 6 th week Longitudinal muscle coat forms at 10-15 th week At 7 th week lumen is filled with cells but few vacuoles are present. At 10 th week lumen is completely restored   due to a process of epithelial layer vacuolization Blood vessels enter the esophageal wall at 7 th month

7. Developmental anomalies Overdevelopment of the internal ridges of the tracheoesophageal septum is proposed as the cause of esophageal atresia and deviation of the tracheoesophageal septum the cause of tracheoesophageal fistula. Failure of development of the tracheoesophageal septum can cause posterior laryngeal clefts. Defects of vacuolization and/or the persistence of diverticulae during the lengthening of the esophagus may be the cause of embryonic cysts, duplication cysts, webs, rings, and congenital stenosis posterior laryngeal cleft

8. OESOPHAGEAL ATRESIA/ TRACHEO- OESOPHAGEAL FISTULA.: Due to: Spontaneous posterior deviation of oesophago tracheal septum. Mechanical factor pushing dorsal wall of foregut anteriorly.

9. Tracheo-oesofageal fistula

10. Curvatures of oesophagus Anterior Curvature: It Follows antero- posterior curve of vertebral column through neck, thorax (posterior mediastinum) & upper abdomen

11.   The lateral deviation of the esophagus has relevance, for example, in the placement of a cervical esophagostomy, treatment of Zenker’s diverticula, or fashioning of an esophagogastrostomy, most being performed on the left side of the neck .

12. Oesophageal constrictions The thoracic oesophagus has three constrictions that are not evident in the collapsed oesophagus but can be visualized when air is insufflated into the oesophagus, as is done during oesophagoscopy or when contrast medium is swallowed for radiological examination. The narrowest part of the oesophagus is at the cricopharyngeal sphincter This is generally at approximately 15cm from the incisor teeth. Below this point, three further anatomical constrictions can be expected along the course of the oesophagus through the thorax and into the abdomen

13. Oesophagus crossed over by the arch of the aorta at approximately 22 cm from the incisor teeth. This is immediately followed by a further constriction occurring at approximately 27 cm from the upper incisor teeth and caused by the left main bronchus crossing over it. These two constrictions are often considered as one constriction . The final constriction, at 38 cm from the incisor teeth, occurs as it passes through the diaphragm just prior to the start of the abdominal part of oesophagus These constrictions are important clinically when instruments are passed through the oesophagus, which can cause serious damage

14. oesophageal Constrictions Site Vertebral level Distance from upper incisor Cricopharynx C6 15 cm Aortic arch T4 22cm Left main bronchus T 5-6 27cm Oesophageal hiatus T10 38cm

15. Foreign body The most common site of oesophageal impaction is at the thoracic inlet The cricopharyngeus sling at C6 is also at this level and may "catch" a foreign body. About 70% of blunt foreign bodies that lodge in the oesophagus do so at this location. Another 15% become lodged at the midoesophagus , in the region where the aortic arch and carina overlap the oesophagus on chest radiograph. The remaining 15% become lodged at the lower oesophageal sphincter (LES) at the gastroesophageal junction.

16. divisions Topographically, there are three distinct regions: C ervical, thoracic, and abdominal 1.Cervical E xtends from the pharyngoesophageal junction to the suprasternal notch( Thoracic inlet ). A bout 4 to 5 cm long

17. 2. Thoracic Extends from the suprasternal notch ( thoracic inlet)  diaphragmatic hiatus. Passes posterior to the trachea, the tracheal bifurcation, and the left main stem bronchus.

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

19. 3.Abdominal Extends from the diaphragmatic hiatus  orifice of the cardia of the stomach. Forms a truncated cone, about 1 cm long.

20. sphincters Two high-pressure zones , prevent the backflow of food. The upper esophageal sphincter & The lower esophageal sphincter.

21. Upper oesophageal sphincter Between pharynx and the cervical oesophagus. Located at C5-C6 level. The UES is a m u scul o car t ila g inous structure. This is formed by fibers of cricopharyngeus , part of the inferior constrictor, which encircles the oesophageal entrance

22. 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.

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

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

25. 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.

26. Bulbous distension of distal oesophagus - vestibule. It corresponds to manometrically defined LES.

27. Attachments of oesophagus Attachment of cranial end of oesophagus Longitudinal muscle attaches to the lamina of the cricoid cartilage by means of a tendon – CRICO OESOPHAGEAL tendon Attachment of tubular oesophagus Attached to trachea, pleura, and prevertebral fascia by several fibrous strands

28. Attachments of distal end Two diaphragmatic crura Phreno oesophageal ligament Phreno oesophageal ligament : Created by blending of the subdiaphragmatic fascia and the endothoracic fascia Also known as LIME’S FASCIA, or A L LI S O N’’’S MEMBRANE Two sheaths - upper inserts into oesophageal tunica muscularis and submucosa - lower inserts into gastric serosa, and mesentry

29. Relations of oesophagus Cervical part Trachea anteriorly RLN, carotid sheath with contents & lower pole of thyroid gland laterally Posteriorly prevertebral fascia Thoracic duct lies behind the left border

30. Oesophagus lies between trachea and vertebral column It enters posterior mediastinum behind aortic arch at T4 Left recurrent laryngeal nerve & thoracic duct are related posteriorly Laterally: left : arch of aorta, vagus nerve, left subclavian artery, pleura Right : azygous vein, pleura Thoracic part In superior mediastinum

31. Thoracic part in posterior mediastinum Anteriorly Tracheal bifurcation , pericardium, right pulmonary artery, tracheobronchial lymph nodes Posteriorly vertebral column, long cervical muscles, right posterior intercostal arteries, thoracic duct , azygous vein and two hemi azygous veins & thoracic aorta

32. I nferiorly. On left is descending thoracic aorta, pleura On right, right pleura and azygous vein Vagal fibers lie in close relation- left vagus anteriorly and right vagus posteriorly

33. Abdominal oesophagus Lies slightly left of median plane Related to the posterior surface of the left lobe of the liver Right border is continuous with lesser curvature & left ends in the cardiac notch Covered by peritoneum anteriorly Posteriorly lie left crus of diaphragm and left inferior phrenic artery

34. Recognition of the different landmark points and the distinct parts of the esophagus is of great help in localizing different lesions and pathological processes when performing barium swallow contrast radiograms and/or endoscopy. Such reference points are very useful to surgeons to plan access routes to the esophagus, such as a right thoracic approach for supracarinal lesions, and a left thoracic approach for lower third esophageal lesions.

35. histology Four coats from outside inwards: Fibrous coat (adventitia) Muscular coat (muscularis propria) Submucous coat Mucous coat

36. Layer of loose, supportive fibrous tissue Conducts major vessels & nerves longitudinally A serosa formed by visceral peritoneum replaces adventitia of intra-abdominal segment of oesophagus oesophagus is unique in that it has no serosal layer, unlike the rest of the digestive tract

37. External longitudinal muscle Internal circular muscle Parasympathetic ganglia forming Auerbach's nerve plexus lies b/w them Upper 1/3: striated muscle Middle 1/3: striated & smooth Lower 1/3: smooth muscle

38. Muscularis propria The muscularis propria is up to 300 μm thick, and consists of the outer longitudinal and inner circular layers typical of the intestine. The longitudinal layer is generally thicker than the circular layer. The longitudinal fibres form a continuous coat around almost the entire length of the oesophagus, except that, posterosuperiorly , 3 – 4 cm below the cricoid cartilage, they diverge as two fascicles that ascend obliquely to the anterior aspect of the oesophagus. Here, they pass deep to the lower border of the inferior constrictor, and end in a tendon that is attached to the upper part of the ridge on the back of the cricoid lamina.

39. The V – shaped space( Laimer's triangle ) between these fascicles is filled by the circular muscle fibres of the oesophagus, which are thinly covered below by some decussating longitudinal fibres and above by the overlapping inferior constrictor.

40. Laimer’s diverticulum is an  extremely rare hypopharyngeal posterior midline true esophageal diverticulum inferior to the cricopharyngeus muscle .

41. Muscle Types: Striated Versus Smooth S triated musculature in the pharynx and particularly in the cricopharyngeal muscle, which is the upper esophageal sphincter muscle (UES). The first sparse smooth muscle fascicles appear 2 to 3 mm caudal to the UES. Farther caudally, progressively more and more smooth muscle bundles replace the striated muscle in both the external and internal layers. The transition between both types is neither abrupt nor confined to individual muscle bundles and lacks any distinct anatomic border. Caudal to the tracheal bifurcation, no striated muscle elements are seen any more. With regard to sphincter function, it might be of interest to be aware that the muscle type of the UES differs completely from that of the LES!

42. The diagram shows the distribution of striated and smooth muscle in adult esophagus The proximal third of the oesophagus consists exclusively of striated (or skeletal) muscle, whereas the distal third is made up of smooth muscle. Between these two regions is a mixture of both striated and smooth muscle . Motility disorders of the esophagus do not involve the proximal esophagus as these are diseases affecting smooth muscle.

43. 3.Submucosa The submucosa loosely connects the mucosa and the muscularis externa. It contains larger blood vessels, nerves and mucous glands. Its elastic fibres are important in the reclosure of the oesophageal lumen after peristaltic dilatation Oesophageal glands - - Oesophageal glands are small tubuloacinar glands lying in the submucosa, each group sending a single long duct through the intervening layers of the gut wall to the surface. They are composed mostly of mucous cells , although they also contain serous cells that secrete lysozyme .

44. 4 Mucosa( Tunica Mucosa )-- The mucous layer is composed of three components : the muscularis mucosae, the tunica propria, and the inner lining of nonkeratinizing stratified squamous epithelium. Muscularis mucosae-- is composed mainly of longitudinal smooth muscle. This forms the long mucosal folds that run in the longitudinal axis of the tube and shapes the small transverse ripple folds at the cardia. All these folds disappear on distention of the esophageal lumen. At the pharyngeal end of the oesophagus it may be absent or represented only by sparse, scattered bundles;below this it becomes progressively thicker. The longitudinal orientation of its cells changes to a more plexiform arrangement near the gastro- oesophageal junction. Lamina propria(tunica propria)-- contains areolar connective tissue, blood vessels, and lymph channels derived from the lower level of the mucosa. It contains scattered groups of lymphoid follicles ( mucosa associated lymphoid tissue ), which are especially prominent near the gastro- oesophageal junction.

45. 3 Epithelium- - non-keratinized, stratified squamous epithelium, continuous with that of the oropharynx. quite thick (300 – 500 μm ). At the base of the epithelium there is a basal lamina, to which epithelial cells are attached by hemidesmosomes. Langerhans cells- Langerhans cells are present in the oesophageal epithelium. They are immature dendritic cells and resemble those found in the epidermis. They perform similar antigen-processing and antigen-presenting roles , which are important in immune stimulation of naive T cells and mucosal defence.

46. Pink, smooth, protective oesophageal mucosa leads to red, mamillated, secretory gastric mucosa across Z (zigzag) line at 38-40 cm from incisors. Higher Z line seen in Barret‟s esophagus .

47. BARRETT’S OESOPHAGUS Barrett’s oesophagus develops when the normal oesophageal lining changes from stratified squamous to columnar epithelium This metaplastic epithelium increases the risk of developing adenocarcinoma of the oesophagus .  In the new AJCC edition, cancers whose epicenter is in the lower thoracic esophagus, EGJ, or within the proximal 5 cm of the stomach (cardia) that extend into the EGJ or esophagus are stage grouped similar to adenocarcinoma of the esophagus

48. 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. Blood supply The inferior thyroid artery supplies the cervical esophagus. Branches of the bronchial arteries and branches directly off of the aorta supply the proximal and distal thoracic esophagus, respectively. Finally, branches of the left gastric and inferior phrenic artery supply the abdominal esophagus. A relatively constant branch connects the left gastric and inferior phrenic arteries, called the Belsey artery.

49. The venous supply is also segmental. From the dense submucosal plexus , the venous blood drains into the superior vena cava. Upper 3 rd ->inferior thyroid vein-> brachiocephalic veins Middle 3 rd ->azygous vein->SVC Lower 3 rd -> left gastric vein-> portal circulation

50. The rd lymphatics from the proximal 1/3  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. Surgical Importance : Submucosal lymphatics explain why tumours may extend long distance before obstructing lumen May also explain high recurrence r a tes Bidirectional lymph flow may explain retrograde tumour seeding if flow is blocked Lymphatic drainage

51. Nerve supply The oesophagus also receives its innervation from dual sources. The sympathetic and parasympathetic supplies. Innervation is received from the vagus as well as the spinal nerves Its sympathetic supplies, both motor and sensory, are from the spinal segments of T1–T10. Sympathetic and parasympathetic innervation regulates smooth muscle activity and glandular secretion.

52. The upper striated muscles of the oesophagus are supplied by multiple small branches arising from the recurrent laryngeal nerves as well as postganglionic sympathetic fibres from the middle cervical ganglia. The more distal smooth muscle fibres of the lower oesophagus are supplied by the oesophageal plexus , a meshwork of parasympathetic and sympathetic fibres hosted by the vagus and recurrent laryngeal nerves below the level of the lung roots

53. Intrinsic innervation of the oesophagus is provided by the thin nerve fibres and numerous ganglia of the intramural myenteric and submucosal plexi . Auerbach’s plexus (also known as the myenteric plexus) is formed by the ganglia that lie between the longitudinal and the circular layers of the tunica muscularis. -Auerbach’s plexus regulates contraction of the outer muscle layers Meissner’s plexus (also known as the submucous plexus) is formed by those ganglia that lie in the submucosa. -Meissner’s plexus regulates secretion and the peristaltic contractions of the muscularis mucosae

54. Achalasia cardia Achalasia results from degeneration of the ganglionic neurons within the myenteric plexus Characterized by a failure of relaxation of the lower oesophageal sphincter on swallowing with absence of peristalsis in the oesophagus . Primary achalasia is idiopathic in aetiology while secondary achalasia occurs in Chagas’ disease and following antireflux surgery