The immune system is the bodies defense against invaders and is located in all body tissues with concentration in the mucosal surfaces and skin.
Its evolution when living things change over time NOT adaptation oops I am sorry for the mistake!!
<span>The average human red blood cell is roughly 6 to 8 micrometers wide. The width of a pin is this problem is defined as 1000 micrometers. Assuming we use the smallest size of a blood cell, then we divide 1000 by 6, and we find that roughly 166.66 (or 166 if you are rounding down) red blood cells will fit.</span>
