<span>The macrophage is the cell responsible for detecting, engulfing and destroying pathogens and apoptotic cells. These cells process and present antigens (foreign materials) to immunocompetent cells and thus they are the key mediators in the development of all immune reactions.</span>
Viscosity refers to the speed at which a substance can flow (i.e. the thickness of the substance/its ability to flow). I think that's the closest the English language gets.
The Central Nervous system is made out of spinal cords that connect to the brain.
Water is the body's most indispensable nutrient. Indispensable means the most essential, in this case, it's water.
