Cutaneous arterioles
Meta arterioles – resistance vessels
Capillaries – large surface area for heat
exchange
Venules – large sub papillary venous
plexus
AV anastamosis – more prominent in
acral regions
Resting blood flow - 10-15ml/ min/100g of skin
Exposure to cold – falls to one tenth of resting flow i.e 1ml/min/100g
Exposure to heat – increase ten times , produces heavy circulatory load –unconciouness
Regional variation in Cutaneous blood flow
Skin color and blood flow
Skin needs little O2
0.3ml/min/100g (compared to )
So nervous >metabolic control
Nervous control – sympathetic supply
alone
Under resting condition
During exposure to heat – four steps
AV anastomoses dilate
Progressive Cutaneous dilation
sweat gland activation
Bradykinin produces dilation
During exposure to cold
Red reaction- within 10 sec , due to
histamine and bradykinn , local response
Flare – spreading redness, after few min,
mediated by axon reflex
diffusely spreading irregular
redness
Wheal - local exudation and edema due
to histamine and substance p