DISEASES OF THE CIRCULATORY SYSTEM
Anatomical considerations: The chest-cavity is called thorax. If the front ribs are cut away, we will find filling up the greater portion of the chest, three organs—two lungs on either side and the heart in the center. The lungs are full of air and their function is to transfer oxygen from the air to the impure blood brought into the lungs thereby oxygenating or purifying the blood.
The heart is a hollow muscular bag, having two chambers on each side of it, right and left. The heart- muscles are endowed with property of rhythmically contracting, with sides contracting synchronously. The contractions produce sounds, which can be represented as: Lubb—Dupp—pause the first sound (Lubb) is booming and somewhat prolonged, the second sound (Dupp) is a sharp thud; there is a nominal pause between the two sounds but a distinct pause between the end of the second and commencement of the first sound.
The right side of the heart receives impure or venous blood from every part of the body and sends it on to lungs to be charged with oxygen. The left side receives back the purified (or oxygen charged) blood from the lungs and sends the pure (or arterial) blood into every part of the body. The venous blood is dark in colour, the arterial scarlet. The venous blood obtained by cutting any of the blue-looking veins, does not spurt but trickles down or flows out; the arterial blood obtained by opening an artery, issues in jerks or spurts—the spurt corresponding with the contractions of the heart, and is therefore rhythmical.
The points worth bearing in mind are: —
- That the heart-sounds occur rhythmically and can be best heard by placing the ear or the chest-piece of the stethoscope near the left nipple. If the sounds are not rhythmical or both are not heard distinctly, that is a disease.
- That the push with which purified blood is sent into the arteries causes a rebound in their elastic walls, producing what is called the pulse. A pulse is a measure to a very great extent of the condition and working power of the heart.
- That arteries become smaller and smaller when they are called arterioles; in them pulsation (or the elastic recoil of the walls of the arterioles, as the result of impact of blood squirted out with force by the heart may be continued; ultimately, these arterioles divide and sub-divide into almost invisible branches which are called capillaries, because of their fineness. Here, there is no pulsation; and here, the purified blood comes into contact with the body- cells and begins to become impure. This impure blood is gradually collected into bigger vessels called veins.