The Oesophagus Lecture 1 PDF

The oesophagus Lecture 1  Learning objectives Describe the pplied n tomy nd physiology of esoph gus Describe the clinic l fe tures, investig tions nd principles of m n gement of benign disorders of esoph gus a a a a...

The oesophagus Lecture 1  Learning objectives Describe the pplied n tomy nd physiology of esoph gus Describe the clinic l fe tures, investig tions nd principles of m n gement of benign disorders of esoph gus a a a a a a a a a a a a Surgic l n tomy The oesophagus is a muscular tube, approximately 25 cm long, mainly occupying the posterior mediastinum and extending from the upper oesophageal sphincter (the cricopharyngeus muscle) in the neck to the junction with the cardia of the stomach. The musculature of the upper oesophagus, including the upper sphincter, is striated. This is followed by a transitional zone of both striated and smooth muscle with the proportion of the latter progressively increasing so that, in the lower half of the oesophagus, there is only smooth muscle. It is lined throughout with squamous epithelium. The parasympathetic nerve supply is mediated by branches of the vagus nerve that has synaptic connections to the myenteric (Auer- bach’s) plexus. Meissner’s submucosal plexus is sparse in the oesophagus. a a a Physiology The main function of the oesophagus is to transfer food from the mouth to the stomach in a coordinated fashion. The initial movement from the mouth is voluntary. The pharyngeal phase of swallowing involves sequential contraction of the oropharyngeal musculature, closure of the nasal and respiratory passages, cessation of breathing and opening of the upper oesophageal sphincter. Beyond this level, swallowing is involuntary. The body of the oesophagus propels the bolus through a relaxed lower oesophageal sphincter (LOS) into the stomach, taking air with it. This coordinated oesophageal wave which follows a conscious swallow is called primary peristalsis. It is under vagal control, although there are speci ic neurotransmitters that control the LOS. The upper oesophageal sphincter is normally closed at rest and serves as a protective mechanism against regurgitation of oesophageal contents into the respiratory passages. It also serves to stop air entering the oesophagus other than the small amount that enters during swallowing. The LOS is a zone of relatively high pressure that prevents gastric contents from re uxing into the lower oesophagus The normal LOS is 3–4 cm in length and has a pressure of 10–25 mmHg. f fl Secondary peristalsis is the normal re lex preceded by a conscious swallow. Tertiary contractions are non-peristaltic waves that are infrequent (