First blood enters into the top right chamber, the right atrium, stop there for a moment then drops down into the bottom right chamber, the right ventricle. When your heart beats the used blood in the bottom right chambers shoots out of the heart and through an artery into you lungs.
indicator - (chemistry) a substance that changes color to indicate the presence of some ion or substance; can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction.
chemistry any of various substances such as litmus or phenolphthalein that indicate the presence absence or concentration of another substance or the degree of reaction between two or more substances by means of a characteristic change especially in color 3 ecology an indicator species 4