Imagine you are examine a specimen of blood under a microscope to look at red blood cells. Why might it be important to know the magnification of the lens you are using?

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.