Context: 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. The cells develop in the bone marrow and circulate for about 100 -- 120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds (one minute). Approximately a quarter of the cells in the human body are red blood cells. Nearly half of the blood's volume (40 % to 45 %) is red blood cells.\n\nQuestion: where does red blood cell formation occur in adults? OK. Let's think. My stream of consciousness:
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To answer the question, consider the following: The cells develop in the bone marrow and circulate for about 100 -- 120 days in the body before their components are recycled by macrophages. The answer is in the bone marrow.
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