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tional Disturbance and a Morbid Condition of the Blood—Their frequent
W West un
E. Burgess deellish
Fig.1. Exhibits the relation of the heart & great vessels to the chest walls & to the different regions of the chust. A. supra. Inviulur region. B. flaviiniar:
HEART AND GREAT VESSELS.
TOPOGRAPHY OF THE HEART AND GREAT VESSELS.
A THOROUGH acquaintance with the topography of the heart and great vessels is a necessary prelude to an investigation of the diseases to which they are subject. I shall, therefore, begin by describing the position of the circulatory organs, and their relation to the parietes of the chest.
The heart, covered by its investing membrane, occupies the lower portion of the anterior mediastinum, lying obliquely across the chest, with its base above and its apex below, the direction of its longer axis being from above downwards, forwards, and to the left. Above, the organ is kept in position by the great vessels, and below by the attachment of its pericardial covering to the diaphragm. Anteriorly, its base is on a level with the third sterno-costal articulation, and its apex with the sixth, so that virtually the entire organ extends from the third to the sixth costal cartilage, and transversely from about half an inch to the right of the sternum to within the same distance of the left nipple. Posteriorly, the base ļies opposite the sixth and seventh dorsal vertebræ.
To the right of the sternum, between the third and fifth ribs, lie a portion of the right auricle and the upper portion of the right ventricle ; behind the sternum lies the greater portion of the right ventricle, a small portion of the left, and the roots of the great vessels; to the left of the sternum lies the left auricle, on a level with the third costal cartilage and the upper part of the third intercostal space, and below it almost the whole of the left ventricle and a small portion of the right ventricle towards the apex. The whole of the anterior surface of the heart is overlapped by the lungs, except a small triangular portion of the right ventricle. The space where the ventricle is uncovered and
comes into apposition with the chest walls is bounded on one side by a line drawn from mid-sternum, opposite the fourth costal cartilage, obliquely downwards and outwards across the lower margin of the fourth left sterno-costal articulation to the lower margin of the fifth left cartilage ; on another, by a line drawn from the same part of the fifth left cartilage obliquely downwards and inwards across the sixth cartilage, and thence along the lower margin of the sixth cartilage to a line drawn vertically down the middle of the sternum ; and on the other, by a line corresponding to the mesian line of the sternum, and extending from the fourth to the sixth rib. The vertical side of this triangle ordinarily measures during tranquil respiration about two inches, and the diagonal about two and a half inches, but the extent of the uncovered area varies at every stage of respiration, according to the degree to which the lungs are inflated. It is also affected by change of posture, being larger in the erect than in a recumbent posture, inasmuch as not only does the heart fall backwards and upwards under cover of the lung when a recumbent posture is assumed, but the upward pressure of the stomach and bowels also tends to push it in the same direction.
All the valves of the heart are seated behind a portion of the chest walls of about an inch in diameter. The pulmonary valves lie under the left border of the sternum opposite its junction with the third left costal cartilage; the aortic valves a little lower and nearer to the mesian line ; the mitral and tricuspid valves as near as possible in the mesian line, on a level with the third intercostal space, the tricuspid being in front and the mitral behind. The second right and the second left sterno-costal articulations are the spots where the sounds of the aorta and the sounds of the pulmonary artery are respectively heard in greatest intensity, and hence the second right cartilage has been named the aortic cartilage and the second left the pulmonary cartilage.
The aorta springs from the base of the left ventricle, and lies about an inch behind the sternum, opposite the third intercostal space. Thence it ascends inclining gradually to the right, until it reaches the second costal cartilage on the right side, whence it curves across the superior sternal region on a level with the lower border of the first costal cartilage, and, passing backwards and downwards towards the left side of the third dorsal vertebra, rests ultimately upon the left side of the bodies of the fifth and sixth vertebræ. In the first part of its course it rests upon the right pulmonary artery and the left side of the trachea, whilst the superior vena cava lies on its right side and the pul