Exercise 4. Read and translate the text. The heart is the muscular pump in the centre of the chest that beats continuously and rhythmically to send blood to the lungs and the rest of the body

Anatomy of the Heart

The heart is the muscular pump in the centre of the chest that beats continuously and rhythmically to send blood to the lungs and the rest of the body. It is located on the diaphragm between the lower borders of the lungs, occupying the middle of the mediastinum. It is covered ventrally by the sternum and the adjoining parts from the third to the sixth costal cartilages. The organ is about 12 cm long, 8 cm wide at its broadest part, and 6 cm thick. The weight of the heart in men averages between 280 and 340 g and in women, between 230 and 280 g. Much of the heart consists of myocardium, a special type of muscle. The heart muscle is supplied with oxygen and nutrients by 2 coronary arteries.

The internal surface of the heart is lined with a smooth membrane, called endocardium, and the entire heart is enclosed in a tough, membranous bag, the pericardium. A thick central muscular wall, the septum, divides the heart cavity into right and left halves. Each half consists of an upper chamber, called an atrium, and a larger lower chamber, called a ventricle. The right atrium receives deoxygenated blood from the entire body via 2 large veins called the venae cavae. This blood is transferred to the right ventricle and pumped to the lungs via the pulmonary artery to be oxygenated and to lose carbon dioxide. The left atrium of the heart receives oxygenated blood from the lungs (via the pulmonary veins); this blood is transferred to the left ventricle and then pumped to all tissues in the body.

The valves of the heart include the tricuspid valve, the bicuspid (mitral) valve, the semilunar aortic valve, and the semilunar pulmonary valve. The sinoatrial node in the right atrium of the heart initiates the cardiac impulse, causing the atria to contract. These one-way valves at the exits from each chamber ensure that blood flows in only 1 direction. As resistance to blood flow through the general circulation is much greater than resistance through the lungs, the left side of the heart must contract more forcibly than the right one that’s why it has greater muscular bulk.

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