Answer to the Friday Whatsit for January 7, 2011
Congratulations to lovely neighbor Gina for correctly guessing the Friday Whatsit! These are red blood cells, also called erythrocytes (from the Greek erythros meaning “red” and cyte meaning “cell.” People sometimes substitute kytos meaning “hollow” instead of cyte).
Mammals are the only group of vertebrates* with red blood cells that lack nuclei at maturity. All other vertebrates (birds, reptiles, amphibians and fish) have red blood cells with nuclei.
The main function of red blood cells is to carry oxygen from the lungs to the rest of the body. To do this, red blood cells are rich with a molecule called hemoglobin, which binds to oxygen using iron.
*vertebrates = animals with spinal cords. These chordates include humans, birds, reptiles, amphibians and fish. Examples of invertebrates (animals without spinal columns) are jellyfish, flies, spiders, corals and worms. Invertebrates far outnumber vertebrates in terms of number or individuals and number of species.