<P> The hypodermis acts as an energy reserve . The fats contained in the adipocytes can be put back into circulation, via the venous route, during intense effort or when there is a lack of energy providing substances, and are then transformed into energy . The hypodermis participates, passively at least, in thermoregulation since fat is a heat insulator . </P> <P> The integumentary system has multiple roles in homeostasis . All body systems work in an interconnected manner to maintain the internal conditions essential to the function of the body . The skin has an important job of protecting the body and acts as the body's first line of defense against infection, temperature change, and other challenges to homeostasis . Functions include: </P> <Ul> <Li> Protect the body's internal living tissues and organs </Li> <Li> Protect against invasion by infectious organisms </Li> <Li> Protect the body from dehydration </Li> <Li> Protect the body against abrupt changes in temperature, maintain homeostasis </Li> <Li> Help excrete waste materials through perspiration </Li> <Li> Act as a receptor for touch, pressure, pain, heat, and cold (see Somatosensory system) </Li> <Li> Protect the body against sunburns by secreting melanin </Li> <Li> Generate vitamin D through exposure to ultraviolet light </Li> <Li> Store water, fat, glucose, vitamin D </Li> <Li> Maintenance of the body form </Li> <Li> Formation of new cells from stratum germanium to repair minor injuries </Li> <Li> Protect from UV rays . </Li> <Li> Regulates body temperature </Li> </Ul> <Li> Protect the body's internal living tissues and organs </Li>

What are three functions of the skin or integument