Any of various nearly colorless cells of the immune system that circulate mainly in the blood and lymph and participate in reactions to invading microorganism sorry foreign particles.
One of the cells of the blood, which in mammals one enucleate disks concave on both sides, contains hemoglobin, and carry oxygen to the cells and tissues and carbon dioxide back to the respiratory organs.
Blood gets oxygen then, the blood and oxygen travels to the heart, then from the heart to the lungs, then back to the heart and the heart pumps the blood throughout your body.