Red Blood Cells

Red blood cells are made in the bone marrow, and found in the blood inside blood vessels (veins, arteries, and capillaries).

Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all other cells in the body. So, red blood cells are the way oxygen from the air reaches your cells.

Red blood cells have a concave, flexible shape that allows them to squeeze through small blood vessels.