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The senior population grows every year. Seniors older than 65 years of age now comprise more than 13% of the total population. However, women outlive men. In the 85-and-over age group, there are only 45 men to every 100 women.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Earwax has antimicrobial properties that reduce the viability of bacteria and fungus in the human ear.
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.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.