Mediastinum_1.V1.pptx

Session Goals 1. Learn to recognize the anatomical boundaries of the mediastinum and its subdivisions. 2. Be able to mentally visualize the contents of the mediastinum and their anatomical relationships. 3. Develop skill in identifying mediastinal structures, landmarks, and relationships using clin...

Session Goals 1. Learn to recognize the anatomical boundaries of the mediastinum and its subdivisions. 2. Be able to mentally visualize the contents of the mediastinum and their anatomical relationships. 3. Develop skill in identifying mediastinal structures, landmarks, and relationships using clinical imaging. Learning Objectives 1. Name, locate, and identify, in images and on the cadaver, the components of the thoracic cage, the mediastinum and its boundaries and subdivisions; describe the location of the mediastinum relative to the lungs and vertebrae. Cardiac Ultrasound https://www.youtube.com/watch?v=0ZsK8HMBclo Mediastinum = middle septum (referring to middle septum of the thorax) ubdivisions of the mediastinum From: Moore and Agur, 2007. e sternum forms the anterior portion of the horacic cage in the midline parts to the sternum: 1. manubrium 2. body 2. xiphoid process Joints between parts of the sternum: a) Manubriosternal joint between manubrium and body = sternal angle b) Xiphi-sternal joint between body and xiphoid process Note: the sternal angle is palpable ubdivisions of the mediastinum Transverse thoracic plane Superior Inferior -divides the superior from the inferior portions of the mediastinum Anterior Middle Posterior Note: the sternal angle and the transverse thoracic plane are at the T4/5 vertebral level From: Moore and Agur, 2007. Learning Objectives 1. Name, locate, and identify, in images and on the cadaver, the components of the thoracic cage, the mediastinum and its boundaries and subdivisions; describe the location of the mediastinum relative to the lungs and vertebrae. Ask yourself: • At what vertebral level does the mediastinum begin? • What vertebral level separates the superior mediastinum from the inferior mediastinum? • At what vertebral level does the mediastinum end? • Which ribs articulate with the manubrium? Body of sternum? Xiphoid process Learning Objectives 2. Name, locate, and identify, in the cadaver and images, the contents of the superior mediastinum and their relationships to other local structures. Contents of the superior mediastinum ymus or thymic remnants anches of the internal thoracic (mammary) vessels ft and right brachiocephalic veins and upper 1/2 of Superior Vena Cava ortic Arch with three branches: brachiocephalic A., left common carotid A., and left subclavian A achea ophagus oracic duct and lymphatic trunks ft and right phrenic nerves; left and right vagus nerves; left recurrent laryngeal branch of the uperficial part of the cardiac plexus. aratracheal, brachiocephalic, and tracheobronchial lymph nodes. T 4/5 intervertebral disc = level of the Transverse Thoracic Plane  Approximate position of the Transverse thoracic plane Level of Superior mediastinum Approximate position of the Transverse thoracic plane Superior Vena Cava Formed by union of left and right brachiocephalic veins Major tributary: azygous vein right S V C Aorta Three parts in the thorax: a. Ascending aorta (part that leaves heart) b. c. Aortic arch (in superior mediastinum) Descending thoracic aorta Transverse Branches of the aortic arch: Thoracic  1. Brachiocephalic trunk Plane 2. Left common carotid 3. Left subclavian Descending thoracic aorta Organization of the major structures of the superior mediastinum from anterior to posterior…. Thymus Major Veins Major Arteries Trachea Esophagus Thoracic duct and lymphatic trunks (not shown here are initially posterior then move more anteriorly) The superior mediastinum also contains: …lymph nodes …nerves Phrenic nerves Vagus nerves Left recurrent laryngeal nerve (branch of the left vagus) …branches of the internal thoracic vess Organization of the superior mediastinum From anterior to posterior…. Thymus Veins Arteries Trachea Esophagus Thoracic duct Lymph nodes (scattered from A-P) anterior Learning Objectives 2. Name, locate, and identify, in the cadaver and images, the contents of the superior mediastinum and their relationships to other local structures. Ask yourself: • What vertebral level separates the superior mediastinum from the inferior mediastinum? Is this the same in the erect vs. the supine patient? • Which vessels are most anterior in the superior mediastinum? Most posterior? • What are the 4 arteries of the superior mediastinum and where are they located? Where do they arise? Learning Objectives 3. Name, locate, and identify, in the cadaver and in images, the structures of the anterior mediastinum and their relationships to other local structures. Contents of the anterior mediastinum. 1. 2. 3. 4. Loose connective tissue and adipose Lymph nodes Inferior portion of the thymus or thymic remnants Branches of the internal thoracic (mammary) vessels Approximate position of the Transverse thoracic plane Radiograph of thymus in a Pre-pubescent child Some little branches of the internal thoracic vessels run medially into the anterior mediastinum Most mediastinal masses occur in the Anterior mediastinum https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2727971/ e thymoma with calcifications (black arrow) and enlarged paratracheal lymph nodes (white arro Learning Objectives 3. Name, locate, and identify, in the cadaver and in images, the structures of the anterior mediastinum and their relationships to other local structures. Ask yourself: • What is the primary occupant of the anterior mediastinum in adults? Learning Objectives 4. Name, locate, and identify, in the cadaver and in images, the structures of the middle mediastinum and their relationships to other local structures; describe the functional and clinical significance of these relationships. 1. 2. 3. 4. 5. 6. 7. Contents of the middle mediastinum. Heart and fibrous and serous pericardia. Inferior ½ of Superior Vena Cava and termination of the azygous vein Pulmonary Trunk and left and right pulmonary arteries Ascending aorta Pulmonary veins Phrenic nerves and accompanying pericardiophrenic vessels Deep part of cardiac plexus Fibrous Pericardial Sac in relation to the Thoraco-abdominal Diaphragm From: Moore and Agur, 2007. Note: the fibrous sac is FUSED to the superior surface of the thoracoabdominal diaphragm. Hence, the pericardial sac AND ITS CONTENTS move with the diaphragm. Pericardium 3 layers: Fibrous (a protective, outer, stabilizing container) Parietal serous (lines fibrous sac) Visceral serous (adheres to the surface of the heart itself) Pericardial during Actual relationship Schematic of heart pushing into serousdevelopment pericardial sac eart and pericardial sac Note: the fibrous pericardium functions to maintain the heart in place within the middle mediastinum, while it vigorously beats. The slippery interface between the two serous layers of pericardium: parietal and visceral, allows for relatively unimpeded movement of the heart within the container: the fibrous pericardium. Visceral layer of serous pericardium Opened pericardial sac, anterior view Empty pericardial sac, anterior view ransverse thoracic plane Transverse sinus Oblique sinus : Ventral rami of C3, 4, and 55 Learning Objectives 4. Name, locate, and identify, in the cadaver and in images, the structures of the middle mediastinum and their relationships to other local structures; describe the functional and clinical significance of these relationships. Ask yourself: • What is the tissue composition of the fibrous pericardial sac? Does this mean it is distensible or not? • What separates the esophagus from the heart? • Where does the azygous vein drain into the SVC? Be as specific as possible. • What IS the oblique pericardial sinus? Learning Objectives 5. Name, locate, and identify, in the cadaver and in images, the contents of the posterior mediastinum and their relationships to other local structures; describe the functional and clinical significance of these relationships. Contents of the posterior mediastinum. ding thoracic aorta gus and esophageal plexus (from vagus nerves) s, hemiazygous, and accessory hemiazygous veins c duct and lymphatic trunks or mediastinal lymph nodes (tracheobronchial nodes, etc.) erves c splanchnic nerves* avertebral sympathetic trunks lie posterior to the pleural sacs surrounding the lungs and thus d to be contents of the mediastinum. The thoracic splanchnic nerves leave the paravertebral sy course toward the midline and are thus located in the mediastinum. T 4/5 level Clemente, 5th ed. Thoracic course of the Vagus Nerves, anterior view Note: In this image, the thoracic vertebral column has been removed to permit visualization of the esophagus and parts of the vagus nerves in the poster mediastinum. Thoracic course of the Vagus NN., posterior view Azygous system of veins and thoracic duct in the posterior body wall (anterior view) Note: The thoracic duct first courses through the posterior mediastinum then into the superior mediastinum. Once in the superior mediastinum is runs from a very posterior position, alongside the esophagus, further towards the left and into a more anterior position in order to drain into the left venous angle. acheobronchial Lymph nodes Note: As with many structures, these are found in more than 1 subdivision of the mediastinum. In this case, both the superior and in the posterior mediastina. Mediastinal Relationships: viewing mediastinal structures from the right and left pleural cavities W OF THE MEDIASTINUM FROM THE RIGHT (right lung removed) Note: the right vagus passing deep (medial) to the arch of the azygous vein. EW OF THE MEDIASTINUM FROM THE RIGHT Note: the right vagus passing deep (medial) to the arch of the azygous vein. The nerve is diving posteriorly to approach what structure in the posterior mediastinum? OF THE MEDIASTINUM FROM THE LEFT (left lung removed) Note: the left vagus passing superficial (lateral) to the arch of the aorta. EW OF THE MEDIASTINUM FROM THE LEFT Note: the left vagus passing superficial (lateral) to the arch of the aorta. The nerve is diving posteriorly to approach what structur in the posterior mediastinum? Note: the left recurrent laryngeal branch of X (the vagus) branches off the left vagus in the superior mediastinum, then passes deep to the ligamentum arteriosum before coursing superiorly to supply the larynx in the neck. The right recurrent laryngeal branch of X branches from the right vagus at the root of the neck, then loops around the right subclavian artery before coursing superiorly to supply the larynx. other look at the course of the left recurrent laryngeal nerve Superior mediastinum Inferior mediastinum Axial sections through the Mediastinum Transverse section through sterno-clavicular joint (T-3 level) Transverse section through aortic arch at T-4 vertebral level st for context….. he internal thoracic arteries and accompanying veins) are branches the subclavian vessels. They run ong the inside of the ribcage n either side of the sternum and ve off small branches in the uperior and the anterior mediastina. ote that the internal thoracic vessels hemselves are NOT in the mediastinum, ut some of their branches are. Moore, 7th ed., Fig. 1.14 Transverse section through pulmonary trunk at level of T-6 Transverse section through heart at level of T-8 Key to Axial CT sections 1=Right brachiocephalic v. 17=T4 vertebral body 33=R. ventricle 2=left brachiocephalic v.18=T6 vertebral body 34=L. atrium 3=brachicephalic A. 19=T8 vertebral body 35=L. ventricle 4=L. common carotid A. 20=arch of aorta 36=inferior R. pulm V. 5=L. subclavian A. 21=anterior mediastinum 37=inferior L.pulm V. 6=esophagus 22=SVC 7=trachea 23=arch of azygous v. 8=R. mainstem bronchus 24=ascending aorta 9=L. main bronchus 25=descending thoracic aorta 10=costal cartilage 26=conus arteriosus 11=sternum 27=pulmonary trunk 12=clavicle 28=R. pulmonary A. 13=axillary v. 29=L. pulmonary A. 14=R. lung30=hemiazygous v. 15=L. lung 31=internal thoracic A. & v. 16=T3 vertebral body 32=R. atrium Modified from Moore and Dalley, 2006 Learning Objectives 5. Name, locate, and identify, in the cadaver and in images, the contents of the posterior mediastinum and their relationships to other local structures; describe the functional and clinical significance of these relationships. Ask yourself: • Does the thoracic duct end in the superior mediastinum? • What landmark is useful for locating the tracheobronchial lymph nodes? What vertebral level is this at? What part(s) of the mediastinum do these nodes occupy? • Why is the right recurrent laryngeal nerve not symptomatic in thoracic pathologies to the extent that the left recurrent is? Learning Objectives 6. Name, locate, and identify the structures and features provided on the session structure list.