Oesophagus digestive system.pptx micro teaching

Introduction The oesophagus (also spelled esophagus) is a vital part of the human digestive system, serving as a muscular conduit for the transport of food and liquids from the pharynx to the stomach. Though often described simply as a “food pipe,” its anatomy and physiology are complex and precisely regulated to facilitate safe and efficient swallowing. The oesophagus not only functions as a passive tube but also actively participates in peristaltic movement, sphincter regulation, and protection against reflux and mechanical damage. Understanding its structure and function is essential for comprehending normal digestion and diagnosing related disorders such as gastroesophageal reflux disease (GERD), achalasia, and esophageal cancer. --- Anatomical Overview 1. Location and Extent The oesophagus is a muscular tube approximately 25 cm (10 inches) long in adults. It extends from the lower border of the cricoid cartilage (C6 vertebral level) to the cardiac orifice of the stomach (T11 vertebral level). It passes through three anatomical regions: 1. Cervical part – from C6 to the thoracic inlet (about 4–5 cm long). 2. Thoracic part – from thoracic inlet to the diaphragm (about 18–20 cm long). 3. Abdominal part – from the diaphragm to the stomach (about 1–2 cm long). --- 2. Anatomical Relations a. Cervical oesophagus Anterior: Trachea Posterior: Prevertebral fascia and vertebral column Lateral: Lobes of the thyroid gland, recurrent laryngeal nerves, and carotid sheaths b. Thoracic oesophagus Anterior: Trachea (upper part), left atrium, and pericardium Posterior: Thoracic vertebral bodies, thoracic duct, and descending aorta Lateral: Right pleura, azygos vein (right), thoracic aorta (left), and vagus nerves c. Abdominal oesophagus Anterior: Left lobe of the liver Posterior: Left crus of the diaphragm --- 3. Constrictions of the Oesophagus The oesophagus has four physiological constrictions where its lumen is narrower: 1. Upper oesophageal sphincter (UES) – at the cricoid cartilage (C6 level) 2. Aortic arch constriction – at T4 level 3. Left main bronchus constriction – at T5 level 4. Diaphragmatic constriction – at T10 level (oesophageal hiatus) These constrictions are clinically important during endoscopy, nasogastric tube insertion, or ingestion of caustic substances. --- 4. Oesophageal Sphincters The oesophagus has two major sphincters: a. Upper Oesophageal Sphincter (UES) Formed mainly by the cricopharyngeus muscle and the inferior pharyngeal constrictor. Function: Prevents air from entering the oesophagus during breathing and prevents reflux into the pharynx. b. Lower Oesophageal Sphincter (LES) A physiological sphincter located at the junction with the stomach (gastroesophageal junction). Formed by: Circular smooth muscle thickening, the diaphragmatic crura, and an oblique angle (angle of His) at the gastric cardia. Function: Prevents gastric contents from refluxing into the oesophagus.