Encyclopedia of Homeopathy

184 •SERIOUS AILMENTSCIRCULATORY SYSTEMThe circulatory, or cardiovascular, system consists of the heart, the bloodvessels, and the blood itself. It continuously supplies blood to every tissuein the body, providing oxygen, a variety of nutrients, minerals, hormones,antibodies, and clotting agents. It removes metabolic waste products.How the system worksThe human body’s complex network of bloodvessels is powered by a central pump—theheart (see below). Blood is pumped outthrough the aorta into all the major arteries.These subdivide into arterioles andcapillaries, through the walls of whichnutrients pass into tissues or organs.Contractions of the heart muscle pumpblood along the arteries. Blood flow alongveins is assisted by the contraction ofmuscles in the limbs. Valves prevent itfrom flowing backward. Many of thediseases of the cardiovascular system ariseeither from the constriction (angina) orblockage (stroke) of blood vessels,from malfunctioning valves, or fromproblems with the pumping action ofthe heart (palpitations).Transportation systemCapillaries collect the waste products ofmetabolism (see page 188), such as carbondioxide, and drain into venules and veins,which carry blood back to the heart andlungs. The portal system connects the smallintestine to the liver. Nutrient-rich blood iscarried by the portal vein from the digestiveorgans to the liver, where nutrients areabsorbed for processing or stored untilthey are needed.Superior vena cavaPulmonary arteriesHeart(see diagram, below)Inferior vena cavaBLOOD SUPPLIES An average male adult hasbetween 5 and 6 quarts (liters) of blood,which is circulated around the body by meansof an extensive network of arteries (shownin red) and veins (shown in blue), bothof which extend into all bodily tissue. Bloodcontains red blood cells that carry oxygen,white blood cells that fight infection, and bloodplatelets, which prevent leakage from bloodvessels. Just over half the volume of bloodis plasma, a straw-colored fluid consistingmainly of water, in which substances suchas nutrients and hormones are carried.AxillaryarteryAortaTHE HEART There are two chambers,an atrium and a ventricle, on eachside of the heart. The left side takesoxygenated blood from the lungsand pumps it around the body. Theright side takes deoxygenated bloodfrom around the body and pumps itto the lungs.Superior vena cava carries deoxygenatedblood from head and armsRight atriumInferior vena cava carries deoxygenatedblood from lower bodyAorta carries oxygenated blood,and branches into major arteriesPulmonary artery—the only arteryto carry deoxygenated blood—branches into each lungLeft atriumValvesLeft ventricleSeptum is a thick muscle walldividing heart in two verticallyRight ventricle