This dissection represents the first stage of the cardiovascular system dissection. The anterior wall of the trunk has been removed to expose the thoracic and abdominal cavities. Situated just posterior to the sternum and costal cartilages, the pericardial sac, which surrounds the heart, is clearly visible and framed by the lungs. Notice the aortic arch arising from the pericardial sac to send its large branches into the upper limb and neck. To the right of the aorta, the brachiocephalic veins converge to form the superior vena cava.