Red blood cells (RBCs), also known as erythrocytes, are the most abundant type of blood cell in the human body. They are essential for the transport of oxygen from the lungs to the body's tissues, and for the transport of carbon dioxide, a waste product of metabolism, from the tissues back to the lungs for exhalation.
Abnormalities in red blood cell production or function can lead to various medical conditions, including anemia (a deficiency in the number or function of red blood cells), polycythemia (an excess of red blood cells), sickle cell anemia, and thalassemia.
Key points:
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Shape and Structure: Red blood cells are small, flexible, and biconcave in shape, which provides a large surface area for the exchange of gases and allows them to pass through tiny capillaries.
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Hemoglobin: Hemoglobin is the protein that gives red blood cells their red color. It binds to oxygen in the lungs to form oxyhemoglobin and releases oxygen in the body's tissues. Hemoglobin also helps carry some carbon dioxide back to the lungs for exhalation.
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Lifespan: Red blood cells are constantly produced in the bone marrow, and typically circulate in the bloodstream for about 120 days. Old and damaged red blood cells are removed from circulation by the spleen and liver.
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Production: The production of red blood cells is regulated by the hormone erythropoietin, which is released by the kidneys in response to low oxygen levels in the blood. This stimulates the bone marrow to produce more red blood cells.
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Hematocrit: Hematocrit is a blood test that measures the proportion of red blood cells in the blood. It is expressed as a percentage of the total blood volume.