United States or Bulgaria ? Vote for the TOP Country of the Week !
We will now sum up, and put together in their order, the different things we have learned about the circulation of the blood through the body. R.A., right auricle; L.A., left auricle; R.V., right ventricle; L.V., left ventricle; A, aorta; P.A., pulmonary artery; P.V., pulmonary veins; V.C.s., Vena cava superior; V.C.i., Vena cava inferior.
It may be a thick and clumsy ear or a beautifully delicate one; long and narrow or short and broad, may have a neatly formed and distinct lobule, or one that is heavy, ungainly, and united to the cheek so as hardly to form a separate part of the auricle, may hug the head closely or flare outward so as to form almost two wings to the head.
Now this is actually so: in some the auricle presents itself as a sanguinolent vesicle, as a thin membrane containing blood, as in fishes, in which the sac that stands in lieu of the auricles is of such delicacy and ample capacity that it seems to be suspended or to float above the heart.
On the other hand, we see a great advance in the structure of the heart, which is found underneath the gills in the shape of a centralised muscular tube, and is divided into an auricle and a ventricle. Later on the lamprey advances still further, and gets a skull, five cerebral vesicles, a series of independent gill-pouches, etc.
To understand the physiology, pathology and the best treatment for broken compensation, it is necessary to study the physics of the circulation under the different conditions. With the mitral valve insufficient, a greater or less amount of blood is regurgitated into the left auricle, which soon becomes dilated.
If the left ventricle is unable properly to empty itself against the increased resistance ahead, the left auricle will contain too much blood, and with the right ventricle sufficient, there will be an accentuation of the second pulmonic sound and it may become louder than the second aortic sound, showing a cardiac deficiency.
The heart muscle, endeavoring to compensate for the over-exertion, may become much thickened, making the ventricles smaller, and so fail to do its duty in properly pumping forward the blood which rushes in from the auricle. Or the heart wall may by exhaustion become thinner, making the ventricles much too large, and unable to send on the current.
The blood thus purified and oxygenated is carried back to the heart, again rich, red and bright, and laden with life-giving properties and qualities. Upon reaching the left auricle of the heart, it is forced into the left ventricle, from whence it is again forced out through the arteries on its mission of life to all parts of the system.
Venous pulsation in the neck is generally marked, showing an impeded contraction of tile right auricle. If the auricles are heard or found by instrumental readings to contract more frequently than the ventricles, the trouble is quite likely to be a heart block from disease in the heart itself, in the bundle of His.
In the Dipneusts the auricle of the heart is divided by an incomplete partition into two halves. Only the right auricle now receives the venous blood from the veins of the body. The left auricle receives the arterial blood from the pulmonary veins.
Word Of The Day