Chapter 4. Heart

Big Picture

The pericardium is a sac that encloses the heart, akin to the pleura that encloses the lungs. The pericardium and the heart are located in the middle of the thorax, between T4 and T8 vertebrae. The pericardium has parietal and visceral layers.

Pericardial Sac

The parietal pericardium is composed of an external fibrous layer (fibrous pericardium) and an internal serous layer (serous pericardium) (Figure 4-1A and B).

• Fibrous pericardium. A strong, dense collagenous tissue that blends with the tunica externa of the great vessels and the central tendon of the diaphragm.
• Serous pericardium. Lines the inner surface of the fibrous pericardium.
• Pericardial space. Lies between the serous layer of the parietal pericardium and the visceral pericardium.
• Visceral pericardium (epicardium). A serous layer that intimately follows the contours of the heart surface. At the root of the heart, the visceral pericardium is contiguous with the serous pericardium, analogous to the visceral and parietal pleura of the hilum of each lung.

The pericardial sinuses are subdivisions of the pericardial sac and consist of the following spaces:

• Transverse sinus. Lies posterior to the ascending aorta and the pulmonary trunk and anterosuperior to the left atrium and the pulmonary veins.
• Oblique sinus. Lies posterior to the heart and is surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferior vena cava.

The pericardium receives its blood supply from the pericardiacophrenic vessels and branches from the bronchial and esophageal vessels. It is innervated by visceral sensory fibers from the phrenic and vagus nerves and the sympathetic trunks.

Big Picture

The heart has the following three layers (Figure 4-1B):

• Epicardium. The outer layer, also known as the visceral pericardium.
• Myocardium. The middle layer, consisting of cardiac muscle responsible for contraction of the heart.
• Endocardium. The inner layer, consisting of endothelial cells that line the lumen of the four chambers.

Anatomy of the Heart

The heart, including its left and right sides, surfaces, borders, and sulci (Figure 4-1C to F), art described in a variety of ways.

Right and Left Sides of the Heart

The expression “right side of the heart” refers to the right atrium and the right ventricle, which collect systemic deoxygenated blood and pump it into the lungs. By comparison, the “left ...