Figure 1.
Factors that determine skin temperature in the core:shell concept of thermal balance. The superficial tissues of the body are regarded as an insulating shell around the inner core in which heat is produced as a byproduct of metabolism. The large arrow represents fraction of this heat lost from the body via the evaporative transfer from the respiratory tract, about 15 - 25%. The small arrows represent the remainder of the body heat, lost from the body surface by convective and evaporative transfer to the environment. Skin temperature, uniform in this model, settles at an equilibrium level. In cool and neutral environments this level is the temperature that produces a sufficient gradient relative to ambient temperature to carry the body heat production (less respiratory loss) away convectively. In warmer conditions, evaporation is responsible for an increasing share of the total heat loss and prevents skin temperature from increasing along with environmental temperature