Physiology and Hygiene for Secondary Schools by Francis M. Walters;A.M.
page 51 of 527 (09%)
page 51 of 527 (09%)
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aorta, and is similar in all respects to the right semilunar valve.
*Differences in the Parts of the Heart.*âMarked differences are found in the walls surrounding the different cavities of the heart. The walls of the ventricles are much thicker and stronger than those of the auricles, while the walls of the left ventricle are two or three times thicker than those of the right. A less marked but similar difference exists between the auricles and also between the valves on the two sides of the heart. These differences in structure are all accounted for by the work done by the different portions of the heart. The greater the work, the heavier the structures that perform the work. [Fig. 17] Fig. 17â*Diagram of the circulation*, showing in general the work done by each part of the heart. The right ventricle forces the blood through the lungs and into the left auricle. The left ventricle forces blood through all parts of the body and back to the auricle. The auricles force blood into the ventricles. *Connection with Arteries and Veins.*âThough the heart is in communication with all parts of the circulatory system, it makes actual connection with only a few of the blood tubes. These enter the heart at its upper portion (Fig. 15), but connect with its different cavities as follows: 1. _With the right auricle_, the superior and the inferior venæ cavæ and the coronary veins. The superior vena cava receives blood from the head and the upper extremities; the inferior vena cava, from the trunk and the |
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