Anatomy of Esophagus.pptx

Anatomy of esophagus

1. ANATOMY OF THE ESOPHAGUS

2. Outline Development Anatomy Blood Supply Venous Drainage Lymphatics Nerve Supply Microscopic Structure

3. Development of the esophagus Develops from the foregut. During the 4 th week, a small diverticulum appears in the ventral wall of pharynx. A “tracheoesophageal septum” gradually separates the ventral respiratory diverticulum from the dorsal part of the foregut. As a result, the pharynx is divided into: A ventral portion, the ‘respiratory primordium’ A dorsal portion, the ‘esophagus’

4. Up to 4 th week, it is very short. Then it elongates rapidly due to the descent of the developing heart and lungs. By the 7 th week, it reaches its final position. The lumen is completely or partially obliterated due to proliferation of its epithelial lining. Recanalization occurs by the end of the embryonic period (after the 8 th week). The muscles developed from the surrounding mesoderm. (striated upper 1/3, mixed 1/3, smooth in the lower 1/3)

5. Introduction Fibromuscular tube approximately 25cm in length. It begins at the inferior border of the cricoid cartilage (C6). Extends to the cardiac orifice of the stomach (T11). Collapsed at rest, dilates during passage of food.

6. Parts of the Esophagus The esophagus is split into the following 3 parts: Cervical part (4cm in length) Extends from the lower border of cricoid cartilage to the superior border of the manubrium sterni Thoracic part (20cm in length) Extends from the superior border of manubrium sterni to the esophageal opening in the diaphragm Abdominal part (1-2cm) Extends from the esophageal opening in the diaphragm to the cardiac end of the stomach

7. Anatomical relations   Anterior Posterior Right Left Cervical and Thoracic Trachea Left recurrent laryngeal nerve Pericardium Thoracic vertebral bodies Thoracic duct Azygous veins Descending aorta Pleura Terminal part of azygous vein Subclavian artery Aortic arch Thoracic duct Pleura Abdominal Left vagus nerve Posterior surface of the heart Right vagus nerve Left crus of the diaphragm    

8. Curvatures Two anteroposterior curvature First, corresponding to the curvature of the cervical spine Second, corresponding to the curvature of thoracic spine Two side-to-side curvatures, both in the direction to the left First, at the root of the neck, before entering the thoracic inlet (T2) Second, before passing in front of the thoracic aorta (T7)

9. Esophageal sphincters Upper Oesophageal Sphincter The upper sphincter is an anatomical, striated muscle sphincter at the junction between the pharynx and oesophagus . It is produced by the  cricopharyngeus  muscle. Normally, it is constricted to prevent the entrance of air into the oesophagus .

10. Lower Oesophageal Sphincter The lower oesophageal sphincter is located at the  gastro- oesophageal junction  .The gastro- oesophageal junction is situated to the left of the  T11 vertebra , and is marked by the change from oesophageal to gastric mucosa. The sphincter is classified as a  physiological  (or functional) sphincter, as it does not have any specific sphincteric muscle. Instead, the sphincter is maintained by four factors: -E sophagus enters the stomach at an  acute angle . -Walls of the intra-abdominal section of the oesophagus are  compressed  when there is a positive intra-abdominal pressure. - Prominent  mucosal folds  at the gastro- oesophageal junction aid in occluding the lumen. -Right crus of the diaphragm has a  “pinch-cock”  effect.

11. Physiological constrictions

12. Clinical importance of esophageal constrictions Likely sites where swallowed foreign bodies may be impacted in the esophagus Likely sites where strictures develop after ingestion of caustic substance These sites have predilection for the carcinoma of the esophagus These are the sites which might be difficult to pass during an OGDS or insertion of gastric tube

13. Blood Supply Cervical part Inferior thyroid arteries Thoracic part Esophageal branches of the descending thoracic aorta and bronchial arteries Abdominal part - Left gastric artery and Left inferior phrenic artery

14. Venous drainage Cervical part Inferior thyroid veins Thoracic part Azygos and hemiazygos veins Abdominal part - Hemiazygos vein, a tributary of inferior vena cava and Left gastric vein, a tributary of portal vein Thus the abdominal part of the esophagus in the site of porto -systemic anastomosis

15. Lymphatics The lymphatic drainage of the esophagus is divided into Proximal third Deep cervical lymph nodes Middle third Superior and posterior mediastinal nodes Distal third - Left gastric and celiac nodes

16. Nerve supply The esophagus is supplied by both the parasympathetic and sympathetic fibres . The parasympathetic fibres originate from the recurrent laryngeal nerves (upper ½) and esophageal plexuses (lower ½) created by the vagus nerves. (Sensory, Motor, Secremotor ) The sympathetic fibres originate from the T5-T9 spinal segments. (Vasomotor)

17. References Last’s Anatomy – 12 th Edition Snell’s Clinical Anatomy by Region – 10 th Edition Clinically Oriented Anatomy by Moore – 8 th Edition Kenhub Anatomy