3. CUTANEOUS BLOOD VESSELS.
Cutaneous arterioles –
dense network just under
dermis.
Meta arteriole – high
resistance conduits
between arterioles &
capillaries.
Cutaneous capillaries –
provide larger surface area
for heat exchange.
Thursday, March 31, 2016
4. CUTANEOUS BLOOD VESSELS.
Venules – extensive sub
papillary venous plexus
Hold large quantity of blood
Important role in maintaining
body temperature.
Arteriovenous anastomosis
– in distal parts of
extremities (hands, feet,
nose, lips & ear lobules)
Wide, low resistance, serves as
shunt
Important in body temperature.
Thursday, March 31, 2016
6. MAIN FUNCTION.
To help in the
Regulation of body
Temperature.
For Nutritive function –
skin need very less
blood.
Thursday, March 31, 2016
7. RESTING BLOOD FLOW.
When the person is at
thermal equilibrium
with the environment at
270
c
10-15ml/min/100 gm
of skin tissue.
Thursday, March 31, 2016
8. EXPOSURE
To Cold –
Minimum sweating
Flow decreases to 1/10th
of normal.
(1ml/min/100gm)
To Heat –
Maximum sweating
Flow increases to 10
times (100-
150ml/min/100gm)
Thursday, March 31, 2016
9. REGIONAL VARIATIONS
Due to A-V
anastomosis in
certain areas as hands,
feet, nose & ear
lobules.
During heat stress A-V
anastomosis blood
flow increases
(75ml/min/100gm)
Thursday, March 31, 2016
10. BLOOD FLOW & SKIN COLOUR.
Basically its due to
pigment present
(Melanin)
But skin colour also
affected by
Amount of blood
Degree of
oxygenation.
Thursday, March 31, 2016
11. REGULATION OF CUANEOUS
BLOOD FLOW
Skin – very less
metabolic activity.
O2 consumption –
0.3ml/min/100gm.
Regulation is mainly by
Nervous Control than
Metabolic Control.
Thursday, March 31, 2016
12. NERVE SUPPLY OF
CUTANEOUS VESSELS
Sympathetic Vaso-
constrictor
At rest Cutaneous
vessels have
sympathetic
constrictor discharge
Its more marked on
A-V anastomosis than
other vessels.
Thursday, March 31, 2016
13. NERVE SUPPLY OF
CUTANEOUS VESSELS
Parasympathetic
Vasodilator – DO not
supply Cutaneous vessels.
Vasodilation due to –
Reduced sympathetic effect.
Local Bradykinin in sweat
glands.
Other local vasodilators.
Thursday, March 31, 2016
16. HYPOTHALAMIC CONTROL
MECHANISM.
Under resting condition.
–
Person at rest with
thermal equilibrium at
270
c – sympathetic
vasoconstrictor has
mild tonic discharge
Keep A-V anastomosis
closed.
Thursday, March 31, 2016
17. HYPOTHALAMIC CONTROL
MECHANISM.
During exposure to
Heat Stress –
sympathetic discharge
decreases
A-V anastomosis,
cutaneous vessels
dilates.
Thursday, March 31, 2016
18. HYPOTHALAMIC CONTROL
MECHANISM.
Sweat glands
activated due to
cholinergic discharge –
local release of
Bradykinin – increases
blood flow to skin.
(150ml/min/100gm)
Heat is dissipated by
radiation, evaporation
& conduction.
Thursday, March 31, 2016
19. HYPOTHALAMIC CONTROL
MECHANISM.
During exposure to
cold stress – Increase
sympathetic discharge
– cutaneous
Vasoconstriction.
Total blood flow
Decreases
1ml/min/100gm.
Leads to heat
conservation.
Thursday, March 31, 2016
20. BARORECEPTOR MEDIATED
REFLEX.
During circulatory stress
as exercise, Hamorrhage
Causes vasoconstriction
Do compensatory
mechanism to divert
blood.
Thursday, March 31, 2016
21. CORTICAL CONTROL
MECHANISM.
Through Cortico-
Hypothalamic
pathway.
Corticohypothalamic
centers
Thoracolumbar
sympathetic cell
bodies
Skin vessels.
Thursday, March 31, 2016
22. CORTICAL CONTROL
MECHANISM.
Blanching of skin –
during fear due to
vasoconstriction
through cortical
mechanism.
Phenomenon of
blushing – during
embarrassment -
corticohypothalamic
control discharge of
sympathetic
cholinergic fibres to
sweat glands
Bradykinin release
Vasodilation.
Thursday, March 31, 2016
24. WHITE REACTION
When pointed object is
stroked over a skin –
Pale strike line appears
Cause – contraction of
precapillary sphincters &
blood drains out of
capillaries & small veins.
Appears in 15 sec.
Thursday, March 31, 2016
25. TRIPLE RESPONSE.
When skin stroke
more firmly with
pointed objects
3 parts response
occurs
Red reaction
Flare
Wheal
Thursday, March 31, 2016
26. Thursday, March 31, 2016
TRIPLE RESPONSE
RED REACTION FLARE WHEAL
TIME 10 SEC AFTER A FEW MIN AT LAST
APPEARS RED LINE DIFFUSELY
SPREADING
IRREGULAR
OUTLINE REDNESS.
SWEALLING &
LOCALISED
OEDEMA.
CAUSE Dilatation of
precapillary
sphincters
Dilatation of
arterioles &
precapillary
sphincters
Increased capillary
permeability with
extravasations of
fluid.
Control No neural control
Local release of
Bradykinin.
Neural control Local release of
histamine &
histamine like
substances by mast
cells.
27. AXON REFLEX.
Definitions:
1. a response elicited by
peripheral nerve stimulation;
attributed to impulses traveling
proximally from the stimulation
site along motor axons,
encountering a branch point, and
then passing distally down the
other branch to activate local
arterioles (to cause vasodilation)
or muscle (to cause contractions).
Thursday, March 31, 2016
28. DERMATOGRAPHIA
Striking triple response
that occurs as an
unusual reaction.
Anything drawn on
skin causes.
Due to excessive
release of Histamine.
Thursday, March 31, 2016
29. REACTIVE HYPEREMIA.
Phenomenon by vessel
control blood flow to the
organ after ischemia due to
occlusion.
Cause – local Hypoxia causes
vasodilatation of arterioles &
precapillary sphincters
So blood flow exceed the
control level when occlusion
is removed.
Thursday, March 31, 2016
30. COLD VASODILATATION.
Exposure to Cold
Cutaneous vasoconstriction
due to hypothalamic
mechanism.
But prolonged & severe
vasoconstriction – Frost
bite.
Thursday, March 31, 2016