did red blood cells ever have a nucleus
Red blood cell Nucleated red blood cells in mammals consist of two forms: normoblasts, which are normal erythropoietic precursors to mature red blood cells, and megaloblasts, which are abnormally large precursors that occur in megaloblastic anemias.
Cell nucleus In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, meaning kernel or seed) is a membrane-enclosed organelle found in eukaryotic cells. Eukaryotes usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others have many.
Paris Peace Accords
Red blood cell In humans, mature red blood cells are flexible and oval biconcave disks. They lack a cell nucleus and most organelles, in order to accommodate maximum space for hemoglobin; they can be viewed as sacks of hemoglobin, with a plasma membrane as the sack. Approximately 2.4 million new erythrocytes are produced per second in human adults.[3] The cells develop in the bone marrow and circulate for about 100â€“120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds (one minute).[4] Approximately a quarter of the cells in the human body are red blood cells.[5][6] Nearly half of the blood's volume (40% to 45%) is red blood cells.