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Thermoregulation in Skin - Anatomy & Physiology (view source)
Revision as of 10:39, 7 August 2008
, 10:39, 7 August 2008→Physiology
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.
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.
===Effect of Fur and Feather===
In mammals with a haircoat and birds with a full plumage, a layer of air is trapped between the surface of the skin and the outer surface of the haircoat or plumage. Air has a low heat capacity and is a poor conductor of heat, therefore it serves as an insulator. The degree of insulation conferred by fur and feather can be altered by increasing or decreasing the thickness of the air layer. This is acheived by the [[Hair - Anatomy & Physiology|arrector pili]] muscle in the dermis.
If this insulating layer of air is replaced by water, heat is readily lost from the skin's surface, leading to a decrease in core bosy temperature and ultimately '''hypothermia'''. The layer is protected by secretions from the skin onto the fur or feathers. In birds, secretions from the [[The Integument of Exotic Species#Avian Skin|uropygial gland]] maintain the water repellant properties of the plumage. In mammals that are regularly exposed to water, a thick layer of subcutaneous adipose tissue of '''blubber''' is present as the insulating air is completely lost and replaced by water.