19.1 Heart anatomy  (Page 4/86)

Pericardial membranes and layers of the heart wall

Surface features of the heart

Inside the pericardium, the surface features of the heart are visible, including the four chambers. There is a superficial leaf-like extension of the atria near the superior surface of the heart, one on each side, called an auricle    —a name that means “ear like”—because its shape resembles the external ear of a human ( [link] ). Auricles are relatively thin-walled structures that can fill with blood and empty into the atria or upper chambers of the heart. You may also hear them referred to as atrial appendages. Also prominent is a series of fat-filled grooves, each of which is known as a sulcus    (plural = sulci), along the superior surfaces of the heart. Major coronary blood vessels are located in these sulci. The deep coronary sulcus    is located between the atria and ventricles. Located between the left and right ventricles are two additional sulci that are not as deep as the coronary sulcus. The anterior interventricular sulcus    is visible on the anterior surface of the heart, whereas the posterior interventricular sulcus    is visible on the posterior surface of the heart. [link] illustrates anterior and posterior views of the surface of the heart.

External anatomy of the heart

Layers

The wall of the heart is composed of three layers of unequal thickness. From superficial to deep, these are the epicardium, the myocardium, and the endocardium (see [link] ). The outermost layer of the wall of the heart is also the innermost layer of the pericardium, the epicardium, or the visceral pericardium discussed earlier.