Surface View of the Heart: The two atria (right and left) are located superiorly, and the two ventricles (right and left) are located inferiorly. The superior and inferior venae cavae enter the right atrium. The pulmonary veins enter the left atrium. The pulmonary trunk exits the right ventricle, and the aorta exits the left ventricle.
The heart consists of four chambers: two atria (singular is atrium) and two ventricles. The thin-walled atria form the superior and posterior parts of the heart, and the thick-walled ventricles form the anterior and inferior portions. Auricles (aw′ri-klz; ears) are flaplike extensions of the atria that can be seen anteriorly between each atrium and ventricle. The entire atrium used to be called the auricle, and some medical personnel still refer to it as such.
Blood enters the atria of the heart through several large veins. The superior vena cava and the inferior vena cava carry blood from the body to the right atrium. In addition, the smaller coronary sinus carries blood from the walls of the heart to the right atrium. Four pulmonary veins carry blood from the lungs to the left atrium.
Blood leaves the ventricles of the heart through two arteries: the pulmonary trunk and the aorta. The pulmonary trunk carries blood from the right ventricle to the lungs. The aorta carries blood from the left ventricle to the body. Because of their large size, the pulmonary trunk and aorta are often called the great arteries.
The coronary circulation consists of blood vessels that carry blood to and from the tissues of the heart wall. The major vessels of the coronary circulation lie in several grooves, or sulci, on the surface of the heart. A large coronary (circling like a crown) sulcus (ditch) runs obliquely around the heart, separating the atria from the ventricles. Two more sulci extend inferiorly from the coronary sulcus, indicating the division between the right and left ventricles. The anterior interventricular sulcus (groove) is on the anterior surface of the heart, extending from the coronary sulcus toward the apex of the heart. The posterior interventricular sulcus (groove) is on the posterior surface of the heart, extending from the coronary sulcus toward the apex of the heart. In a healthy, intact heart, the sulci are covered by adipose tissue, and only after this tissue is removed can they be seen.