<Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The integumentary system comprises the skin and its appendages acting to protect the body from various kinds of damage, such as loss of water or abrasion from outside . The integumentary system includes hair, scales, feathers, hooves, and nails . It has a variety of additional functions; it may serve to waterproof, cushion, and protect the deeper tissues, excrete wastes, and regulate temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, and temperature . In most land vertebrates with significant exposure to sunlight, the integumentary system also provides for vitamin D synthesis . </P> <P> The skin is the largest organ in the body . In humans, it accounts for about 12 to 15 percent of total body weight and covers 1.5 - 2m of surface area . </P> <P> The human skin (integument) is composed of at least two major layers of tissue: the epidermis and dermis . (The hypodermis or subcutaneous layer is not part of the skin .) The epidermis is the outermost layer, providing the initial barrier to the external environment . Beneath this, the dermis comprises two sections, the papillary and reticular layers, and contains connective tissues, vessels, glands, follicles, hair roots, sensory nerve endings, and muscular tissue . The deepest layer, the hypodermis, is primarily made up of adipose tissue . Substantial collagen bundles anchor the dermis to the hypodermis in a way that permits most areas of the skin to move freely over the deeper tissue layers . </P>

What is the main organs of the integumentary system