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Thermoregulation in Skin - Anatomy & Physiology (view source)
Revision as of 10:31, 7 August 2008
, 10:31, 7 August 2008no edit summary
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==Introduction==
When the body's heat production is stable, the blood flowing into the [[Skin - Anatomy & Physiology#Dermis|dermis]] is regulated depending on changes in ambient temperature. The purpose of this regulation is to ensure that the difference in temperature between the skin's surface and the environment remains constant, thus regulating heat loss and maintaining an almost constant body temperature. When heat production increases, blood flow to the '''dermis''' also increases, which, in turn, increases the heat lost from the skin to the same rate as the excess heat production.
==Physiology==
Heat transported from the body core to the skin's surface, will pass through '''subcutaneous adipose tissue''', dermis, and finally to the [[Skin - Anatomy & Physiology#Epidermis|epidermis]], after which, the heat passes through air trapped in [[Hair - Anatomy & Physiology|fur]] or [[Feather - Anatomy & Physiology|plumage]]. Adipose tissue is a poor conductor of heat, therefore, even a thin layer will confer some insulation against heat loss.
The extent of heat lost from the skin is dependent on the amount of blood flow to the dermis. As blood flow decreases due to '''vasoconstriction''' of the '''subcutaneous vessels''', the insulating effect of the skin increases. The more vasoconstriction that occurs, the closer to environmental temperature the skin's surface will become. If blood flow to the dermis increases, however, heat loss through the skin increases as the temperature difference between the skin and the environment also increases. The insulation provided by the adipose tissue can therefore be somewhat bypassed if the blood flow to the dermis is great enough.
Blood flow to the dermis can vary by a factor of 3 to 5, depending on the requirement for heat loss or conservation. This blood flow is regulated by the [[Nervous System - PNS - Anatomy & Physiology|sympathetic nervous system]]. An increase in core body temperature causes a decrease in the tone of the smooth muscle walls of the arterioles due to a reduced impulse frequency in the sympathetic nerve fibres. This casues vasodilation, which in turn, increases cutaneous blood flow and therefore heat loss. The opposite is true for a decrease in core body temperature.