Human Anatomy, Part 2 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2008

Special Section
Cardiovascular system, systema cardiovasculare - Special Section
Heart

The Heart, cor (Greek cardia), is a hollow, four-chambered muscular organ that Functions as a pump. It ejects Blood into the Arterial System during the contraction of the chamber walls (systole) and receives it from the venous trunks during their relaxation (diastole). The rhythmic activity of the heart proceeds in the following sequence: atrial contraction occurs first (systole, lasting 0.1 s), followed by ventricular contraction (systole lasting 0.3 s). The ventricular systole is accompanied by atrial diastole, which lasts 0.7 s, after which ventricular diastole begins. Following a general pause, atrial systole recurs, initiating a new cardiac cycle (Fig. 7A, 7B). Thus, the heart serves as the primary source of mechanical energy driving Blood flow through both the pulmonary and systemic circulations.

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Fig. 7A. Diagram of BLOOD FLOW IN the heart (arrows indicate the direction of blood flow), after I. Ye. Kefeli

The heart has an irregular conical shape, flattened in the anteroposterior direction. It features a base, basis cordis, and an apex, apex cordis.

The Base of the heart is directed upward and to the right, while the apex points anteriorly, downward, and to the left. The base is formed by the atria, with the aorta and pulmonary trunk emerging anterior to it. The SUPERIOR VENA CAVA empties into the right side of the base, the INFERIOR VENA CAVA into its posteroinferior region, the left Pulmonary Veins posteriorly and to the left, and the right pulmonary veins slightly to the right of them (see Fig. 8).

The heart presents the following surfaces: an anterior (sternocostal) surface, facies sternocostalis; an inferior (diaphragmatic) surface, facies diaphragmatica; and a pulmonary surface, facies pulmonalis. The right margin, margo dexter, is sharper and formed by the right atrium, whereas the left margin, margo sinister, is blunter and adjacent to the left lung.

The anterior sternocostal surface (Fig. 9) is formed predominantly by the right ventricle and, to a lesser extent, by the left ventricle and atria. It lies adjacent to the Sternum and the cartilages of the left III–IV Ribs, largely contacting the mediastinal Pleura. The boundary between the ventricles is marked by the anterior interventricular sulcus, sulcus interventricularis anterior, while the atrioventricular boundary is marked by the coronary sulcus, sulcus coronarius. The anterior interventricular sulcus contains the anterior interventricular branch of the left coronary artery, the great cardiac vein, a nerve plexus, and efferent Lymphatic vessels. The coronary sulcus lodges the right coronary artery, a nerve plexus, and lymphatic vessels.

The inferior diaphragmatic surface of the heart (Fig. 9) faces downward and rests upon the Diaphragm. It is formed primarily by the left ventricle, partially by the right ventricle, and by portions of the right and left atria.

Fig. 7B. Valve positions during diastole (a) and systole (b)

On the diaphragmatic surface, the two ventricles border each other along the posterior interventricular sulcus, sulcus interventricularis posterior, which transmits the posterior interventricular branch of the right coronary artery, the middle cardiac vein, nerves, and lymphatic vessels. Near the apex of the heart, the posterior interventricular sulcus merges with the anterior interventricular sulcus, forming the notch of the cardiac apex, incisura apicis cordis. On the diaphragmatic surface, the atria are separated from the ventricles by the posterior part of the coronary sulcus, which contains the right coronary artery, the circumflex branch (a. coronariae sinistrae), the coronary sinus (sinus coronarius), and the small cardiac vein (vena cardiaca parva).

The pulmonary surface, facies pulmonalis, is in contact with the mediastinal Organs and is formed by the two atria, which are well demarcated from each other by the interatrial sulcus, sulcus interatrialis.

The dimensions of an adult heart range within the following limits: length 12–13 cm, width 9–10.5 cm, and anteroposterior dimension 6–7 cm. The average heart mass is 300 g in men, 220 g in women, and 18–20 g in newborns.