Royal Army Medical Corps training pamphlet / War Office.

Date:
1944
Catalogue details

Licence: Public Domain Mark

Credit: Royal Army Medical Corps training pamphlet / War Office. Source: Wellcome Collection.

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    lungs pours into the left side of the heart, when it is once more sent round the body. It will be seen that the heart really contains two distinct pumps, one serving the lungs (pulmonary circulation) and the other the rest of the body (systemic circulation). The course of the circulation (Fig. 17) can be described in more detail as follows :— (a) The vene cave collect all the blood which has passed through the tissues (muscles, skin, kidneys, liver, intestine, brain, bone, nerves, etc.), and pour it into— (b) The right auricle of the heart, which contracts and thus drives the blood through— (c) The tricuspid valve into— | (@) The right ventricle, which contracts, driving the blood through (e) The pulmonary artery into the lungs, where it travels through capillaries exposed to the air. The oxygenated blood then passes into— . (f) The pulmonary veins, which convey it to— ‘(g) The left auricle, which contracts, driving it through— (A) The bicuspid (or mitral) valve into— ( ( 1) The left ventricle which contracts, driving it into— 4) The aorta, the main artery of the body, which dis- tributes it to all parts through branch arteries which divide and stibdivide, becoming smaller and smaller until they terminate in capillaries. The capillaries unite to form small veins which join with other veins, becoming gradually larger and larger until they all unite to form the vene cave. Besides the tricuspid and mitral valves, between the auricles and the ventricles, there are also semilunar valves at the beginnings of the aorta and of the pulmonary artery. The function of all these valves is to ensure that when the heart contracts the blood is driven onwards and does not go the wrong way. Sometimes the valves become diseased and do not close completely. This impairs the function of the heart and may make the person unfit for an active life. 49. The pulse.—Although during exercise and in disease the rate may be much increased, the normal heart beats on the average about 70 times a minute. As the heart contracts, its muscles harden and the apex strikes against the left side of the chest, where the heart beat may be felt. At the same time blood is pumped into the arteries, causing a wave of increased pressure or pulse. This wave occurs with every