Pulmonary artery

“ In primary defects of the pulmonary artery trunk the vast majority afford indubitable evidences of an original inflammatory causation; others are due just as positively to a defective evolution of this vessel from the common arterial trunk. Instances are on record of the complete closure of the pulmonary artery and its conversion into a ligamentous cord: these cases are very rare. In a somewhat larger number a pretty uniform narrowing, sometimes to an extreme degree, and often exhibiting thickened walls, is found. ”

“ In such persons the pulmonary second sound frequently seems to be unusually loud when compared with the aortic second sound, without any evidence of hypertrophy of the right ventricle being present. The determination of the position of the lung establishes the diagnosis in such cases. On the other hand, a lung dilated by emphysema may interpose and completely cover the heart and pulmonary artery, which, though dilated, may thus be masked. ”

“ If the pulmonary artery becomes suddenly impermeable, the pressure in the collateral arteries, which originates partly from the bronchial artery, and partly from those outside of, but in connection with, the lungs, as the pleural, etc., is sufficient to prevent a venous reflux, but not sufficient to overcome the entire resistance in the lungs and to drive the blood beyond the capillaries into the left auricle. ”

“ The blood coming from the upper extremities of the child finds its way into the right auricle of the heart by means of the descending vena cava, thence into the right ventricle, and out into the pulmonary artery. This artery after birth will lead the blood to the lungs, but before birth, in as much as the lungs are not functioning, the lungs can not accommodate this amount of blood, so it passes directly into the arch of the aorta by means of the ductus arteriosus, and thence into the general circulation. ”

“ The arterial blood is brought from the lungs by two wide, thin-walled pulmonary veins, Fig. 58, V.p.s., V.p.d. They leave the lungs somewhat caudad to their middle region, near the point of entrance of the bronchii and the pulmonary arteries, pass mediad in a direction almost at right angles to the long axis of the body, and enter the left auricle at the same point.
Blood leaves the heart through five large vessels: (1) the pulmonary artery, (2) the two aortic arches, (3) the right subclavian, (4) the primary carotid. ”

“ Another effect of shrinkage of lung is to uncover the aorta in the second intercostal space on the right side, or the pulmonary artery in a corresponding situation on the left side. The pulsation of these arteries may then be perceived by the touch, and perhaps, also, by the eye. This effect should not lead to the error of inferring the existence of aneurism. Shrinkage of the upper lobe of the left lung may cause considerable elevation of the heart, also enlarging considerably the space within which is felt the cardiac impulse. ”

“ There is everywhere a mutual anastomosis and inosculation of the arteries with the veins, and they severally transmit both blood and spirit, by certain invisible and undoubtedly very narrow passages. Now if the mouth of the pulmonary artery had stood in like manner continually open, and nature had found no contrivance for closing it when requisite, and opening it again, it would have been impossible that the blood could ever have passed by the invisible and delicate mouths, during the contractions of the thorax, into the arteries; for all things are not alike readily attracted or repelled ”

“ If the lung of an animal be injected from the pulmonary artery, there is produced a complete filling of the vessels of the bronchial wall and into the subepithelial layer—a fact the more interesting that a similar event can scarcely be produced by a filling of the bronchial artery. ”

“ It is evident that congestion of the minute branches of the pulmonary artery would not give to the lung-tissue a bright-red color, and if such a condition exists it must be due to injection of the bronchial vessels. It is by no means proven that such injection ever precedes pneumonic engorgement. In the stage of engorgement that portion of the lung which is involved in the pneumonic process does not collapse when the thoracic cavity is opened. ”

“ A rigid tricuspid valve has been found to be the cause of obstruction at the pulmonary orifice, the pulmonary valves themselves being normal. A few autopsies have revealed obstructions at the pulmonary artery, caused not so much by valvular defect as by aneurisms, tumors of the pericardium or of the anterior mediastinum, enlarged bronchial glands, or pressure of a solidified lung. ”

“ Moreover, when they appoint the pulmonary artery, a vessel of great size, with the coverings of an artery, to none but a kind of private and single purpose, that, namely, of nourishing the lungs, why should the pulmonary vein, which is scarcely so large, which has the coats of a vein, and is soft and lax, be presumed to be made for many—three or four different—uses? ”

“ COMPLICATIONS AND SEQUELÆ.—One, if not the gravest, complication which can arise during the formation and duration of heart-clot is the production of an embolus of the pulmonary artery, completely filling up its cavity, arresting respiration, and causing sudden death by asphyxia. More frequently smaller portions of heart-clot become detached and are transported farther along by the blood-current. ”

“ There are, as everyone knows, three sigmoid or semilunar valves situated at the orifice of the pulmonary artery, which effectually prevent the blood sent into the vessel from returning into the cavity of the heart. ”

“ Beneke has found in his records of arterial measurements that the pulmonary artery greatly exceeds the aorta in circumference up to the age of thirty. After that period the aorta begins to increase with relatively greater rapidity, until in the forties it exceeds the pulmonary artery in size, and it maintains its superiority from that time forward. The aorta continues to increase in circumference throughout life, but after the age of fifty this increase is considered a senile dilatation rather than an actual growth. ”

“ These diseased valves are thickened, very firm, fibrous, or even calcified. In other cases the obstruction consists of abundant warty elevations, so numerous that they are equally effective in preventing the passage of blood as the united valves. The size of the opening is sometimes extremely reduced, measuring only five millimeters in diameter. The pulmonary artery is most generally less in size than normal, but never becomes reduced to the same extent as its orifice, unless it has likewise suffered from inflammatory disease; otherwise its walls remain thin, resembling the venæ cavæ. ”