The mediastinum

The mediastinum is defined as 'the space which is sandwiched between the two pleural sacs'. For descriptive purposes the mediastinum is divided by a line drawn horizontally from the sternal angle to the lower border of T4 (angle of Louis) into superior and inferior mediastinum. The inferior mediastinum is further subdivided into the anterior in front of the pericardium, a middle mediastinum containing the pericardium itself with the heart and great vessels, and posterior mediastinum between the pericardium and the lower eight thoracic vertebrae (Fig. 22).

The pericardium

The heart and the roots of the great vessels are contained within the conical fibrous pericardium, the apex of which is fused with the adventitia of the

Sternopericardial Ligament

great vessels and the base with the central tendon of the diaphragm. Anteriorly it is related to the body of the sternum, to which it is attached by the sternopericardial ligament. The 3rd-6th costal cartilages and the anterior borders of the lungs; posteriorly, to the oesophagus, descending aorta, and vertebra T5-T8, and on either side to the roots of the lungs, the mediastinal pleura and the phrenic nerves.

The inner aspect of the fibrous pericardium is lined by the parietal layer of serous pericardium. This, in turn, is reflected around the roots of the great vessels to become continuous with the visceral layer or epicardium. The lines of pericardial reflexion are marked on the posterior surface of the heart (Fig. 23) by the oblique sinus, bounded by the inferior vena cava and the four pulmonary veins, which form a recess between the left atrium and the pericardium, and the transverse sinus between the superior vena cava and left atrium behind and the pulmonary trunk and aorta in front.

Its great importance means no excuse need be offered for dealing with the heart in considerable detail.

The heart is irregularly conical in shape, and it is placed obliquely in the middle mediastinum. Viewed from the front, portions of all the heart chambers can be seen. The right border is formed entirely by the right atrium, the left border partly by the auricular appendage of the left atrium but mainly by the left ventricle, and the inferior border chiefly by the right

Auricle Atrium
Fig. 23 The transverse and oblique sinuses of the pericardium. In this illustration the heart has been removed from the pericardial sac, which is seen in anterior view.
Visceral Pericardium
Fig. 24 The heart, (a) anterior and (b) posterior aspects.

ventricle but also by the lower part of the right atrium and the apex of the left ventricle.

The bulk of the anterior surface is formed by the right ventricle which is separated from the right atrium by the vertical atrioventricular groove, and from the left ventricle by the anterior interventricular groove.

Superior vena cava

Inferior vena cava

Coronary sinus

Fossa oval is

Superior vena cava

Inferior vena cava

Coronary sinus

Fossa oval is

Anterior Venecava

Medial cusp of tricuspid valve

Left ventricle

Pulmonary trunk

Right ventricle

Aorta

Fig. 25 The interior of the right atrium and ventricle.

Medial cusp of tricuspid valve

Left ventricle

Pulmonary trunk

Right ventricle

Aorta

Fig. 25 The interior of the right atrium and ventricle.

The inferior or diaphragmatic surface consists of the right and left ventricles separated by the posterior interventricular groove and the portion of the right atrium which receives the inferior vena cava.

The base or posterior surface is quadrilateral in shape and is formed mainly by the left atrium with the openings of the pulmonary veins and, to a lesser extent, by the right atrium.

How To Get Perfect Abs

How To Get Perfect Abs

The Complete Guide To How to Get Perfect Abs is Here. While other books gear you towards buying a product or a service, this book actually tells you exactly what you need to do to get the abs of your dreams. Getting a six pack and looking good is easier than ever if you follow the instructions in this book. This book does not just tell you what workout machines to use, but how to think, what to eat, what not to eat and how to exercise to get the six pack abs that you have longed for but never thought that you would get.

Get My Free Ebook


Responses

  • ALEKSANDRA
    What is central mediastinum?
    6 years ago
  • NEAVE
    What are the important features of the mediastinum?
    6 years ago

Post a comment