The oxygen-carrying capacity of whole blood is determined by its concentration of hemoglobin. If the hemoglobin concentration is below normal—in a condition called anemia—the oxygen content of the blood will be abnormally low. Conversely, when the hemoglobin concentration rises above the normal range—as occurs in polycythemia (high red blood cell count)—the oxygen-carrying capacity of blood is increased accordingly. This can occur as an adaptation to life at a high altitude.
The production of hemoglobin and red blood cells in bone marrow is controlled by a hormone called erythropoietin, produced by the kidneys. The secretion of erythropoietin—and thus the production of red blood cells—is stimulated when the amount of oxygen delivered to the kidneys is lower than normal. Red blood cell production is also promoted by androgens, which explains why the hemoglobin concentration in men is from 1 to 2 g per 100 ml higher than in women.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...