The blood flowing in the veins in which almost all red blood cells (ery­thro­cytes) and plate­lets (throm­bocytes) and nume­rous white blood cells (leu­ko­cytes) are found. A suf­fi­ci­ent num­ber of stem cells for trans­plan­ta­ti­on are only found in healt­hy adults once they have under­go­ne pri­or medi­cal tre­at­ment with a growth factor.