10. ANATOMY OF THE MEDIASTINUM MATERIAL.pptx

Anatomy

1. By Dr B.E Arayombo Anatomy of Mediastinum

2. Definition It is a space located between the right & left pleural cavity and their sacs . the space is sandwiched between the two pleural sacs. It includes all the structures which lie in the intermediate compartments of the thoracic cavity. All of organs between the left and right mediastinal pleurae is called mediastinum. It extends from the sternum anteriorly to the vertebral column posteriorly and from the thoracic inlet superiorly to the diaphragm inferiorly.

3. Mediastinum it contains the central structures between: The two pleural sacs, Sternum & Vertebral bodies are all involved

4. Mediastinum It is divided by a horizontal plane extending from sternal angle to lower border of 4 th thoracic vertebra by transverse thoracic plane into: Superior mediastinum : above the plane Inferior mediastinum : below the plane, it is subdivided into: Anterior mediastinum : in front of pericardium Middle mediastinum : contains heart & pericardium Posterior mediastinum : behind pericardium

5. Events at the Sternal Angle/plane of Louis/Ludwig 1 . Thoracic duct crosses the midline to the left and empties into the left subclavian vein. 2. Left recurrent laryngeal nerve loops under the arch of the aorta . 3. Arch of aorta (aortic arch) is at this level . 4. Trachea (carina)bifurcates to form the 2 main bronchi. 5.The second costal cartilage articulates between the body and manubrium of sternum anteriorly . 6 . Pulmonary trunk bifurcation occurs . 7 . Azygous system of veins drains into the superior vena cava . 8 . S tart of cardiac plexus of nerves. 9 . Ligamentum arteriosum .

6. Mediastinum Regions and Contents… 1. Superior Mediastinum : behind the manubrium (pleura are apart here) thymus gland - most anterior structure, behind manubrium in front of brachiocephalic vein and aortic arch slowly shrinks with age (largest in childhood), replaced largely by adipose 2 . Inferior Mediastinum : separation from superior is at line between sternal angle & intervertebral disc 4- 5. Divided into: a. Anterior - in front of pericardium (thin space) b. Middle - contains pericardium, the heart, phrenic nerves, blood vessels c. Posterior - behind pericardium

7. SUPERIOR MEDIASTINUM BOUNDARIES: Anterior: manubrium sterni Posterior: Upper 4 thoracic vertebrae Superior: Plane of thoracic inlet Inferior: Horizontal plane On each side: Pleura

8. SUPERIOR MEDIASTINUM CONTENTS: FROM BEHIND FORWARD: Esophagus Trachea Arch of aorta and its 3 branches: brachiocephalic, left common carotid and left subclavian arteries Right and left brachiocephalic veins & superior vena cava Thymus gland

9. SUPERIOR MEDIASTINUM OTHER CONTENTS: Nerves: Right & left vagus Right & left phrenic Right & left sympathetic trunks Left recurrent laryngeal Lymphatic structures: Thoracic duct Lymph nodes

10. POSTERIOR MEDIASTINUM BOUNDARIES: Anterior: Pericardium and diaphragm Posterior: Lower 8 thoracic vertebrae Superior: Horizontal plane Inferior: Diaphragm On each side: Pleura

11. POSTERIOR MEDIASTINUM CONTENTS: Esophagus (most anterior structure) Thoracic duct Right & left vagus Descending aorta Azygos & hemiazygos veins Right & left sympathetic trunks & their branches (splanchnic nerves) Lymph nodes

12. MIDDLE MEDIASTINUM The middle mediastinum is the broadest part of the inferior mediastinum. Contents : T he pericardium, The heart, ascending aorta, the lower half of the superior vena cava, the terminal azygos vein, tracheal bifurcation and both main bronchi, the left pulmonary arteries, both pulmonpulmonary trunk and the right and pulmonary veins, the phrenic nerves, the deep part of the cardiac plexus and the tracheobronchial lymph nodes.

13. Anterior mediastinum Anterior mediastinum Location - posterior to body of sternum and attached costal cartilages, anterior to heart and pericardium. It narrows above the fourth costal cartilages, where the pleural sacs come close to each other.

14. ANTERIOR MEDIASTINUM 7 June, 2021 mediastinum & its subdivision 15 Contents : It contains loose connective tissue, the sternopericardial ligaments, a few lymph nodes and the mediastinal branches of the internal thoracic artery. It may sometimes contain part of the thymus gland or its degenerated remains

15. Mediastinal spaces Retrosternal space - lies beween sternum and endothoracic fascia Pretracheal space - lies within superior mediastinum, between trachea, bifurcation of trachea and aortic arch Retroesophagus space - lies within superior mediastinum, beween esophagus and endothoracic fascia

16. Clinical correlates Mediastinitis Mediastinal shift in pneumothorax Mediastinal widening in hemothorax Mediastinal tumours Ant: teratoma , thymoma , thyroid tumours , lymphoma Middle: pericardial cyst, bronchogenic cyst, metastatic ca , aneurysm, cardiomegaly, achalasia, esophageal diverticular. Posterior : ganglioneuroma , neurofibroma , neurilemomma , schwann - cell tumour