Mediastinum (3): Superior Mediastinum - PDF

Mediastinum (3): The Superior Mediastinum – Nerves and Hollow Viscera Prof. Mohammed Z. Allouh Recommended Textbooks & Atlases (Notice: images included in this presentation are adapted from these recommended text...

Mediastinum (3): The Superior Mediastinum – Nerves and Hollow Viscera Prof. Mohammed Z. Allouh Recommended Textbooks & Atlases (Notice: images included in this presentation are adapted from these recommended textbooks and atlases) Moore Clinically Oriented Anatomy, 7th ed. Keith Moore, Arthur Dalley, & Anne Agur. Copyright © 2014 Wolters Kluwer/Lippincott Williams & Wilkins Clinical Anatomy by Regions, 9th ed. Richard S. Snell. Copyright © 2012 Wolters Kluwer/Lippincott Williams & Wilkins. Gray’s Anatomy for Students, 4th ed. Richard L. Drake, A. Wayne Vogl, Adam W. M. Mitchell. Copyright © 2020 Elsevier Inc. Principles of Human Anatomy, 13th ed. Gerard Tortora & Mark Nielsen. Copyright © 2014 Gerard J. Tortora, LLC, Mark T. Nielsen, John Wiley & Sons, Inc. Grant’s Atlas of Anatomy, 13th ed. Anne M. R. Agur, Arthur F. Dalley. Copyright © 2013 Wolters Kluwer Health / Lippincott Williams & Wilkins. Anatomy: A Photographic Atlas, 8th ed. Johannes Rohen, Chihiro Yokochi, Elke Lütjen-Drecoll. Copyright © 2016 Schattauer GmbH and Wolters Kluwer 1 Nerves - Phrenic - Vagus - Left Recurrent Laryngeal 2 1  Phrenic Nerve - Origin: ant. rami of C3, C4, C5 spinal nerves - Sole motor supply to the ?? ( 2/3 of N.F.) - Remaining 1/3 of its nerve fibers are sensory fibers for pericardium, pleura, & peritoneum - Descends in the neck on the ant. surface of scalenus anterior muscle - Enters thorax behind (post. to) the origin of BC vein on each side 3 Right Phrenic Nerve In thorax - *Passes anterior to the root of Right lung* - Descends along the Rt. Side of pericardium to reach the diaphragm - Passes through the caval opening in the diaphragm to supply its undersurface. 4 2  Left Phrenic Nerve In thorax - *Passes anterior to the root of left lung* Lf. Phrenic - Descends along the Lf. Side of pericardium to reach the diaphragm - Penetrates the left dome of diaphragm to supply its undersurface. 5 Attendance 6 3  Vagus Nerve - (L, Wandering) - CN. X - Carries Parasympathetic innervation to the viscera in thorax and Abdomen 7 Right Vagus Nerve - Enters thorax anterior to Rt. subclavian artery  Rt. recurrent laryngeal nerve - *Passes posterior to the root of Right lung* - Accompanies esophagus in posterior mediastinum - Rotates around esophagus in a clock-wise manner to become  Posterior vagal trunk 8 4  Left Vagus Nerve - Descends on the Lf. Side of aortic arch  Lf. recurrent laryngeal nerve - *Passes posterior to the root of Left lung* - Accompanies esophagus in posterior mediastinum - Rotates around esophagus in a clock-wise manner to become  Anterior vagal trunk 9 10 5  Left Recurrent Laryngeal Nerve - Arises from Lf. vagus as it crosses the aortic arch - Hooks around the arch of aorta posterior to ligamentum arteriosum - It then ascends in the groove between trachea & esophagus on the left side - Supplies all muscles acting on left vocal cord, except one. 11 Hollow Viscera - Trachea - Esophagus 12 6  Trachea A fibro-cartilaginous tube that extends from C6  sternal angle (T4/T5) In deep inspiration it descends to the level of ? Structure Ant-Lat: U-shaped bars of hyaline cartilage Post.: smooth muscle (trachealis) Terminates at the level of sternal angle by dividing into Rt. & Lf. main bronchi. Rt. bronchus: Wider, shorter & more vertical Lf. Bronchus: Narrower, longer & more horizontal Relations of Lf. bronchus? Inferior to aortic arch, and anterior to esophagus & descending aorta 13 Tracheal Relations in the Superior Mediastinum Anterior: Manubrium Thymus (in children) Left BC vein Brachiocephalic trunk Posterior: Esophagus Recurrent laryngeal nerve Thoracic duct 14 7  Computed Tomography (CT) Scan of the Superior Mediastinum Identify the three structures anterior to the trachea. Identify the location of the esophagus. Identify the thoracic vertebral level. 15 Esophagus Begins in the root of the neck as a continuation of the pharynx opposite to C6 vertebra Descend in the Superior Mediastinum just directly posterior to (behind) the trachea As it descends in the posterior Mediastinum, it shifts from midline to the left side of the vertebral bodies anterior to the ? 16 8  Esophagus In posterior Mediastinum: it is related anteriorly to the Left atrium of the heart *Esophagus constitutes the primary posterior relationship to the heart* It Leaves thorax at T10 by passing through the esophageal opening in the diaphragm 17 Esophageal Constrictions Esophagus has 3 anatomic & physiologic constrictions: 1st: Cervical constriction (pharyngeo-esophageal stricture) where esophagus joins the pharynx at its upper end - at C6 - 15 cm from upper incisors 2nd: Bronchoaortic constriction (also known as Thoracic stricture) where esophagus is crossed by left bronchus & aortic arch - at T5 - 25 cm from upper incisors 3rd: Diaphragmatic constriction Where esophagus passes through diaphragm - at T10 - 41 cm from upper incisors 18 9  Significance of Esophageal Constrictions 1- Delay of passage of substances (food & liquids) at these sites  Strictures develop after drinking caustic fluids T5 2 2- Difficult regions to pass the endoscope through during GI endoscopy 3- Common sites of carcinoma of the 3 esophagus T10 19 10