Mediastinum 2, Superior Mediastinum-Part 1 PDF

Mediastinum (2): The Superior Mediastinum – Veins & Arteries Prof. Mohammed Z. Allouh Recommended Textbooks & Atlases (Notice: images included in this presentation are adapted from these recommen...

Mediastinum (2): The Superior Mediastinum – Veins & Arteries 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 Superior Mediastinum Boundaries Sup.: Superior thoracic aperture Inf.: Transverse Thoracic Plane (TTP) Ant.: Manubrium sterni Post.: Upper ? Thoracic vertebrae 2 1  Contents of Superior Mediastinum From Anterior to Posterior: 1- Thymus (only in children) 2- Veins: Brachiocephalic (BC) veins & SVC 3- Arteries: Arch of aorta & its 3 branches 4- Nerves: Phrenic & Vagus nerve 5- Trachea (Respiratory System) 6- Esophagus (Digestive System) 7- Thoracic duct (Lymphoid System) 3 Axial CT of the Superior Mediastinum 4 2  Thymus The primary lymphoid organ where T-lymphocytes mature and become immunocompetent (functionally active) After puberty, the thymus undergoes involution and is eventually replaced by fat in adulthood. 5 The Veins - Brachiocephalic veins (Right & Left) - Superior Vena Cava (SVC) 6 3  Brachiocephalic Veins Formed posterior to sterno-clavicular (SC) joints by the union of IJV & subclavian vein. The left vein crosses midline to the right side just directly posterior to the manubrium and anterior to the arteries.  More than twice as long as the right vein Both veins unite at the inferior border of 1st right CC to form SVC Clinical Question: Which vein is more susceptible to injury? 7 8 4 9 Superior Vena Cava Returns blood from all structures superior to diaphragm except lungs and heart. Formed by union of two BC veins Starts posterior to inferior border of 1st right costal cartilage Ends at the level of 3rd right CC  enters the right atrium of the heart In sup. Mediastinum: It is located anterior to the right of the trachea 10 5  Attendance 11 Arteries in the Superior Mediastinum - The Arch of the Aorta - Three branches: 1- Brachiocephalic Trunk 2- Left Common Carotid 3- Left Subclavian 12 6  The Aorta The largest artery in the human body Divided into 4 parts: 1- Ascending aorta: - covered by pericardium  lies within the middle mediastinum - gives 2 branches to the heart 2- Arch of aorta: - in the superior mediastinum - gives 3 branches 3- Descending thoracic aorta: - in posterior mediastinum (T5-T12) - gives many branches: post. Intercostals, bronchial, pericardial, & esophageal 4- Abdominal aorta: - at the level of T12-L4 (13 cm) 13 Arch of the Aorta Curved continuation of the ascending aorta into the superior mediastinum Route: - Starts posterior to the 2nd right CC  Arches superior, posterior, to the left  Reaches its apex on the left side of trachea & esophagus  Passes over the root of the left lung  Arches inferior, posterior, to the left side - Terminates on the left side of IV disc of T4/T5 14 7  Arch of the Aorta As the aortic arch loops over the root of the left lung: Ligamentum arteriosum passes from its inferior surface to the root of the left pulmonary artery Ligamentum arteriosum: The remnant of fetal ductus arteriosus, which shunts blood from pulmonary arteries to the aorta in the fetus Ductus arteriosus is obliterated within ?? of birth to become ligamentum arteriosum 15 16 8  Brachiocephalic Trunk 1st & largest branch of the aortic arch It arises between the trachea (posteriorly) and the Lf. BC vein (anteriorly) Ascends superolateral to the right side of the body Terminates posterior to the right SC joint By dividing into ? & ? In general, there is no brachiocephalic trunk on the left side of the human body. 17 Left Common Carotid Artery 2nd branch of the aortic arch Arises posterior to the left BC trunk Begins anterior to trachea, then on its left side Enters the neck by passing posterior to the left SC joint 18 9  Left Subclavian Artery 3rd and most posterior branch of the arch Arises to the left of the trachea, & leaves chest posterior to left SC joint Loops over the superior surface of the 1st rib, below the clavicle, and posterior to scalenus anterior muscle to enter the upper limb At the outer border of the 1st rib it becomes the ? artery 19 10