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When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Alcohol acts as a diuretic. Eight ounces of water is needed to metabolize just 1 ounce of alcohol.
Vaccines prevent between 2.5 and 4 million deaths every year.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.