Fact
Red blood cells throw away their own nucleus
They give up the ability to divide, repair, or make anything, in exchange for room to carry oxygen.
Maturing human red blood cells eject their nucleus and most organelles, becoming little more than flexible sacks of haemoglobin. That is what makes them so efficient – and why they cannot repair themselves and last only about 120 days before being recycled. Most other mammals do the same; birds and reptiles do not.