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.
The term vitamin D also refers to metabolites (products of metabolism) and other analogues of these substances. Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B radiation. Vitamin D plays an important role in the maintenance of organ systems (body tissues).