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
see story