where does red blood cell production occur in adults
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.[2] 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).[3] Approximately a quarter of the cells in the human body are red blood cells.[4][5] Nearly half of the blood's volume (40% to 45%) is red blood cells.
Blood Blood accounts for 7% of the human body weight,[3][4] with an average density around 1060 kg/m3, very close to pure water's density of 1000 kg/m3.[5] The average adult has a blood volume of roughly 5 litres (11 US pt),[4] which is composed of plasma and several kinds of cells. These blood cells (which are also called corpuscles or "formed elements") consist of erythrocytes (red blood cells, RBCs), leukocytes (white blood cells), and thrombocytes (platelets). By volume, the red blood cells constitute about 45% of whole blood, the plasma about 54.3%, and white cells about 0.7%.