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The second sound is, without doubt, caused by the sudden closure of the semilunar valves of the pulmonary artery and the aorta, at the moment when the contraction of the ventricles is completed. Muscular Fibers of the Ventricles.
The upper part of this ring of woody vessels, formed by the prolongation of the horns of the original semilunar band, is narrower than the lower part, and slightly less compact. This petiole after clasping the stick had actually become thicker than the stem from which it arose; and this was chiefly due to the increased thickness of the ring of wood.
From the right ventricle a large vessel called the pulmonary artery passes to the lungs, and from the left ventricle a large vessel called the aorta arches out to the general circulation of the body. The openings from the ventricles into these vessels are guarded by the semilunar valves. Each valve has three folds, each half-moon-shaped, hence the name semilunar.
Near the upper surface of the petiole, beneath two exterior ridges, there are two other small circular groups of vessels. The semilunar band has been converted into a complete ring of very hard, white, woody tissue, with lines radiating from the centre. The three groups of vessels, which, though near together, were before distinct, are now completely blended.
Displaced semilunar cartilage, and a three months' job. The man's worth thirty-five shillings a week. And there! I'm hanged if the woman with the rheumatic arthritis isn't round in her bath-chair again. She's all sealskin and lactic acid. It's simply sickening to see how they crowd to that man. And such a man! You haven't seen him. All the better for you.
Between the clavicles another pulsatile swelling was easily felt but hardly seen, which was doubtless the arch of the aorta, as by putting the fingers on it one could feel a double shock, synchronous with distention and recoil of a vessel or opening and closing of the semilunar valves. Madden also mentions several analogous instances on record.
Locking of joints is more often met with as a result of injuries, especially in fractures occurring in the region of the elbow. In certain injuries of the semilunar menisci of the knee, also, the joint is liable to a variety of locking, which differs, however, in many respects from that described above.
Each valve usually consists of two semilunar flaps attached to opposite sides of the vessel wall, each flap having a small sinus on its cardiac side. The distension of these sinuses with blood closes the valve and prevents regurgitation.
When the neuralgia involves branches of two or of all three trunks, or when it has recurred after temporary relief following resection of individual branches, the removal of the semilunar ganglion, along with the main trunks of the maxillary and mandibular divisions, should be considered.
Separate the aorta from the other blood vessels and cut it entirely free from the heart, care being taken to leave enough of the heart attached to the artery to insure the semilunar valve’s being left in good condition. After tying or plugging up the holes in the sides of the artery, pour water into the small end and observe the closing of the semilunar valve.
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