the Cardiovascular System Mediastinum & pericardium

3rd 4th

T5 MEDIASTINUM lies between the right and left mediastinal pleura in the chest. Extend from the sternum anterior to the vertebral column posterior . From the Thoracic inlet (Opening) superior To The diaphragm inf. Highly mobile Contains: Hollow viscera Loss connect. Tissue and Fat Great elasticity Accommodate Movements, volume and Pressure changes

The mediastinum: division It may be divided for purposes of description Into two parts by a slightly oblique plane passing from the junction of the manubrium and body of the sternum (sternal angle) to the lower border of the body of the fourth thoracic vertebra The superior mediastinum the inter-pleural space which lies between the manubrium sterni in front, and the upper thoracic vertebrae behind. This lower portion is The inferior mediastinum subdivided into three parts, The anterior mediastinum: The middle mediastinum The posterior mediastinum

Boundaries and contents of the mediastinum The Anterior Mediastinum Exists only on the left side where the left pleura diverges from the mid-sternal line. It is bounded in front by the sternum, laterally by the pleuræ, and behind by the pericardium. It is narrow, above and widens out below. Its anterior wall is formed by the fifth, sixth, and seventh left costal cartilages. It contains a quantity of loose areolar tissue, some lymphatic vessels, two or three anterior mediastinal lymph glands, and the small mediastinal branches of the internal mammary artery. The Middle Mediastinum Is the broadest part of the interpleural space. It contains the heart enclosed in the pericardium, the ascending aorta, the lower half of the superior vena cava with the azygos vein opening into it, the bifurcation of the trachea and the two bronchi, the pulmonary artery dividing into its two branches, the right and left pulmonary veins, the phrenic nerves, and some bronchial lymph glands. The Posterior Mediastinum: Is an irregular triangular space running parallel with the vertebral column; it is bounded anterior by the pericardium above, and by the posterior surface of the diaphragm below, posterior by the thoracic vertebral bodies from the lower border of the T4-T1. On either side by the mediastinal pleura. It contains the thoracic part of the descending aorta, the azygos and the two hemiazygos veins, the vagus and splanchnic nerves, the esophagus, the thoracic duct, and some lymph glands.  

The contants of the Superior Mediastinum the aortic arch; the innominate artery and the thoracic portions of the left common carotid and the left sub-clavian arteries; the innominate veins and the upper half of the superior vena cava; the left highest inter-costal vein; the vagus, cardiac, phrenic, and left recurrent nerves; the trachea, esophagus, and thoracic duct; the remains of the thymus, and some lymph glands.

Inferior mediastinum: content

Cross Section T8 Mediastinum content

Cross Section T9 Mediastinum content

The Pericardium Outer Fibrous and inner Serous pericardium Serous: is divided into parietal and visceral pericardia (Epicardium) The Small space between them is pericardial Sac filled with pericardial fluid. Pericardial fluid lubricates and reduces friction between the two surfaces. Pericarditis – inflammation of the pericardium Cardiac tamponade – excess fluid in the pericardial cavity.

Anatomical relationships Surrounds heart and bases of pulmonary artery and aorta. Deep to sternum and anterior chest wall. The right phrenic nerve passes to the right of the pericardium. The left phrenic nerve passes over the pericardium of the left ventricle. Pericardial arteries supply blood to the dorsal portion of the pericardium.

Pericardial sinuses There are two Pericardial sinuses: transverse and oblique. The cul-de-sac enclosed between the limbs of the inverted U of the venous mesocardium lies behind the left atrium and is known as the oblique sinus. . The passage between the venous and arterial mesocardia—i.e., between the aorta and pulmonary artery in front and the superior vena cava behind—is termed the transverse sinus Also, the sinus that forms in the pericardial cavity where the dorso-mesentary pericardium reside. Can be used to pass ligature during cardiac surgery.

Inferior Vena Cava Superior Vena Pulmonary Arteries Aorta trunk

Pericardial sinuses