This document discusses the anatomy and physiology of cutaneous blood flow regulation. It notes that cutaneous blood flow at rest is 10-15 ml/min/100g of skin, falling to 1 ml/min/100g with cold exposure and increasing tenfold with heat exposure. Blood flow is primarily regulated by the sympathetic nervous system. Exposure to heat causes arteriole dilation, cutaneous vessel dilation, sweating, and bradykinin-induced dilation. Exposure to cold triggers vasoconstriction. Various reflexes and cortical mechanisms also influence blood flow regulation and skin color changes.

3.  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

6.  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

7.  Skin needs little O2
 0.3ml/min/100g (compared to )
 So nervous >metabolic control
 Nervous control – sympathetic supply
alone

8.  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

11.  Baroreceptor reflex
 Cortical control mechanism
 Blanching of skin
 Phenomenon of blushing

14.  White reaction – due to vasoconstriction
& appears about 15 sec

15.  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

21.  Increased blood flow after a transient
occlusion

22.  Cont’d