the beginning of the journey of the red blood cell starts in the bones (inside it) where there is formation of blood cell. the the aid of the capillary(within it), the red blood cells travels round the body. the deoxygenated blood then goes to the heart in the vena cava. the red blood cell then journey into the right atrium even after the red blood cell has made its way into the heart, the right atrium contracts and then pushes the blood cell via the tricuspid and thereafter into the right ventricle where the right ventricle then contracts and pushes the blood cell out of the heart via the aid of the semi luna.
the red blood cell journey down to the lungs, picks up oxygen and goes back to the heart and enters the left atruim and its contracts and pushes the blood cell via the bicuspid into the left ventricle which pushes the red blood cell out of the heart into the aorta, journey down to the kidney's trunk and lower limb's. the the deoxygenated blood then travels up with the aid of the vena cava. it is a circulatory process. all the process goes round and start again from the beginning
