Circulatory System

             In science, we had just finished learning about the circulatory system and now we are learning about the respiratory system. We are also learning about the circulatory system in health. I will tell you briefly about the circulatory system.

             There are four components in our blood: red blood cells carry oxygen; white blood cells fight diseases and germs; platelets clot blood and repair damaged blood vessels; and plasma is the liquid. There are three blood vessels: veins carry blood towards the heart; arteries carry blood away from the heart; and capillaries are the smallest blood vessels that carry blood to and from the tissue cells. The pathway of blood is that the superior vena cava and the inferior vena cava bring blood to the heart from the body. The blood then enters the right atrium. The right atrium pumps blood through the tricuspid valve into the right ventricle. It pumps blood into the pulmonary artery which takes it to the lungs. In the lungs, the blood gives off CO₂ and takes in O₂. The blood then returns in the heart through the pulmonary vein to the left atrium.  It pumps the blood through the bicuspid (mitral) valve into the left ventricle. The left ventricle pumps blood through a semilunar valve into the aorta. The aorta carries blood to various parts of the body. The whole process then starts all over again.