Land affected or burdened by an easement is called a servient estate, while the land or person benefited by the easement is known as the dominant estate.. If the easement benefits a particular piece of land, it is said to be appurtenant to the land.
Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol.
Vitamin D is normally produced in skin through a robust photolytic process acting on a derivative of cholesterol (ie, 7-dehydrocholesterol) to produce previtamin D, which is then slowly isomerized to vitamin D 3 . Vitamin D 3 is the natural form of vitamin D produced in skin, and vitamin D 2 is derived from irradiation of ergosterol, which occurs to some degree in plankton under natural conditions and is used to produce vitamin D 2 from the mold ergot (which contains as much as 2% ergosterol).