the Cardiovascular System “Mediastinum” By: Dr. Nabil A Khouri MD, MsC, Ph.D

Bony Thorax (Thoracic Cage)

General Structure of thoracic Vertebrae

Thoracic Vertebrae

Mediastinum Is the middle compartment of the thoracic cavity which is situated between the right and left mediastinal surface of the lungs covered by pleura. Boundaries: Anteriorly, the sternum and the costal cartilages. Posteriorly, the bodies of 4-12 thoracic vertebrae. Superiorly, the thoracic inlet. Inferiorly, the diaphragm. Laterally (on each side), the mediastinal pleura

MEDIASTINUM Inferior mediastium First rib “Thoracic inlet” Superior boundaries: Sternal Angle to T4/5 (Inter VD) Inferior boundaries: Middle of Xiphoid process to T9 Diaphragm IX

2 3 4 5 6 7 8 9 Body

The Location of the Heart within the medastinum

The superior mediastinum Located above the heart and therefore lying behind the manubrium sterni contains: the great vessels of the heart                                Level of Manb. Sterni

Contents of sup. mediastinum The arch of the aorta with its three large branches. Right and left brachiocephalic veins. The upper part of the superior vena cava. The vagus (10th cranial), the phrenic and the left recurrent laryngeal nerves. The thymus (in children, or some possible remnants in adults). The trachea. The esophagus. Some lymph nodes.

A transverse section of the thorax, showing the contents of the Anterior, middle and the posterior mediastinum Posterior Mediastiunum

Content of the posterior mediastinum artery thoracic part of the descending aorta veins azygos vein the hemiazygos vein and the accessory hemiazygos vein nerves vagus nerve splanchnic nerves (but not the sympathetic chain[1]) esophagus thoracic duct some lymph glands

Posterior Right side mediastinum Azygos Vein Rt. Prim. Bronch. Esophagus Rt. Vagus N Lymph Nods Sympathetic plexus Pulmonary Veins Pulmonary Arteris Intercostal arteries and veins Rt Phrenic N Br. Ceph. Vein SVC

Left Side Thoracic Cavity 1 2 3 Aorta 4 – Brachio-Ceph. Trunk 5 - Descending Aorta 6 - Left. Main Bronch. 7 - Pulmonary V 8 - Phrinic N and Pericardio-phrenic A

Right Left

Fluid level in Esophagus

Anterior mediastinal nodes Lymphoma

The Pericardium Outer sac – Fibrous Inner - Serous, is a double layered sac –(parietal and visceral pericardium Between the parietal and visceral pericardium is a Small space – the pericardial Cavity It is filled with pericardial fluid (lubricates and reduces friction between the two surfaces). The most inner of these two serous layers actually forms the Epicardium and is in direct contact with myocardium

Filled with Pericardial Fluid Central tendon of the diaphragm The Pericardium Filled with Pericardial Fluid Pericardio-phrenic Ligament Central tendon of the diaphragm

Pericardial sinuses Inferior Vena Cava Superior Vena Pulmonary Arteries Aorta trunk Right Left Pericardial sinuses                               

Pericardial Sinuses Two In number: Lies within the pericardial cavity, at the points where the visceral and parietal pericardia are continuous with one another. The pericardial sinuses are: transverse pericardial sinus (Open “Connected Lt-Rt”) Between the reflections of pericardium onto the aorta and pulmonary trunk superiorly and the pulmonary veins inferiorly oblique pericardial sinus (closed “Not continuous”) The cul-de-sac enclosed located between the limbs of the U lies behind the left atrium and is known as the oblique sinus, It is a recess in the pericardial cavity posterior to the base of the heart bounded laterally by the pericardial reflections on the pulmonary veins and inferior vena cava, and posteriorly by the pericardium overlying the anterior aspect of the oesophagus.

THE Pericardial reflection Right side view Oblique Sinus

Innervations The fibrous pericardium and the parietal layer of the serous pericardium are sensory innervated by the phrenic nerves (C3-C5). The epicardium receives autonomic innervation from the underlying heart. Excessive accumulation of fluid in the pericardial cavity and may lead to the compression of the heart. Restriction of the heart movement may lead to cardiac arrest.

Pericardium Relation

The Heart Wall