The skin

The skin is an organ of double-layered tissue stretched over the surface of the body and protecting it from drying or losing fluid, from harmful external substances, and from extremes of temperaturesee story

Brain

The human brain has three major structural components: the large dome-shaped cerebrum
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Heart and blood Circulation

In passing through the system, blood pumped by the heart follows a winding course through the right chambers of the heart
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Reproduction is accomplished by the union of male sperm and the female ovum. In coitus, the male organ ejaculates more than 250 million sperm into the vagina, from which some make their way to the uterus. Ovulation, the release of an egg into the uterus, occurs approximately every 28 days; during the same period the uterus is
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