Human Anatomy - M.M. Kurepina, A.P. Ozhigova, A.A. Nikitina 2010

Cardiovascular System
Heart

The Heart (from the Greek kardia) is a hollow muscular organ divided into four chambers: the right and left atria and ventricles (Fig. 2.1). The rhythmic contractions of the heart drive the continuous Circulation of Blood through the vessels, thereby supplying our body's Tissues and Organs with a steady stream of oxygen, nutrients, and other substances. At rest, the heart rate ranges from 60 to 80 beats per minute, with each cardiac cycle lasting about 0.8 seconds. Of this duration, atrial contraction (systole) takes 0.1 seconds, ventricular systole takes 0.3 seconds, and the remaining 0.4 seconds consist of general relaxation (diastole) of both the atria and ventricles. Blood returns via the Veins into the atria, and when the atria contract, it is pushed down into the ventricles. During ventricular systole, blood is forced out into the Arteries and distributed throughout the body.

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Fig. 2.1. The Heart and major Blood Vessels:

1 — right and 2 — left atria; 3 — right and 4 — left ventricles; 5 — aorta; 6 — pulmonary trunk; 7 — left Pulmonary veins; 8 — brachiocephalic trunk; 9 — common carotid arteries; 10 — external and 11 — internal carotid arteries; 12 — subclavian arteries and 13 — veins; 14 — internal jugular veins; 15 — brachiocephalic veins; 16 — SUPERIOR VENA CAVA; 17 — azygos vein; 18 — INFERIOR VENA CAVA; 19 — ligamentum arteriosum

The weight of the human heart ranges between 250 and 360 g, varying depending on body size, level of physical activity, and age. As a rule, the heart is larger in men than in women. Radiographs show that the size of the heart corresponds roughly to the volume of an individual's clenched fist.

The broad upper portion of the heart is called the base, and the tapered lower portion is the apex. The heart features two surfaces: the anterosuperior (sternocostal) surface, which is more convex, and the posteroinferior (diaphragmatic) surface, which is flattened; it also has two borders — a blunt left border and a sharper right border (Atlas, Figs. 51, 52). The greater part of the anterior surface of the heart is formed by the right ventricle. The right atrium faces anteriorly, and its appendage, the right auricle, partially covers the Water/144.html">Origin of the aorta as it emerges from the left ventricle. The left ventricle and left auricle are located on the posterior aspect of the heart. The left auricle is smaller in volume than the right, curved, has a notched margin, and lies adjacent to THE ORIGIN OF the pulmonary artery emerging from the right ventricle.

The surface of the heart is marked by sulci that correspond to the boundaries of its internal chambers. These grooves contain adipose tissue, which in well-nourished individuals or cases of pathological obesity may completely cover the musculature of the organ. Encircling the heart closer to its base is the coronary sulcus, which marks the boundary between the atria and the ventricles. It houses the coronary blood vessels. The sulcus wraps around the posterior and lateral aspects of the heart, being interrupted anteriorly where the aorta and pulmonary trunk arise. The anterior and posterior interventricular sulci run along the interventricular septum, with the former shifted slightly to the left. Near the apex of the heart, which belongs to the left ventricle, both interventricular sulci meet. Branches of the coronary vessels run within these grooves.