cutaneous circulation
TRANSCRIPT
DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
CUTANEOUS CIRCULATION
OBJECTIVES
Cutaneous circulation. Cutaneous blood flow- characteristics
features. Regulation of Cutaneous blood flow Cutaneous vascular response
Monday, May 1, 2023
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.
Monday, May 1, 2023
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.
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CUTANEOUS BLOOD FLOW CHARACTERISTIC FEATURES.
Main function. Resting blood flow. Exposure Regional variations Blood flow & skin
colour.
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MAIN FUNCTION. To help in the
Regulation of body Temperature.
For Nutritive function – skin need very less blood.
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RESTING BLOOD FLOW. When the person is at
thermal equilibrium with the environment at 270 c
10-15ml/min/100 gm of skin tissue.
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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)
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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)
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BLOOD FLOW & SKIN COLOUR. Basically its due to
pigment present (Melanin)
But skin colour also affected by Amount of blood Degree of
oxygenation.
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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.
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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.
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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.
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NEURAL CONTROL MECHANISMS
Hypothalamic Control Mechanism.
Baroreceptor mediated reflex.
Cortical control mechanism.
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HYPOTHALAMIC CONTROL MECHANISM.
Temperature Regulation centre of Hypothalamus mediate thermoregulation by increase & decrease of sympathetic discharge to Cutaneous vessels.
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HYPOTHALAMIC CONTROL MECHANISM.
Under resting condition. –
Person at rest with thermal equilibrium at 270c – sympathetic vasoconstrictor has mild tonic discharge
Keep A-V anastomosis closed.
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HYPOTHALAMIC CONTROL MECHANISM.
During exposure to Heat Stress – sympathetic discharge decreases
A-V anastomosis, cutaneous vessels dilates.
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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.
Monday, May 1, 2023
HYPOTHALAMIC CONTROL MECHANISM.
During exposure to cold stress – Increase sympathetic discharge – cutaneous Vasoconstriction.
Total blood flow Decreases 1ml/min/100gm.
Leads to heat conservation.
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BARORECEPTOR MEDIATED REFLEX.
During circulatory stress as exercise, Hamorrhage
Causes vasoconstriction
Do compensatory mechanism to divert blood.
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CORTICAL CONTROL MECHANISM.
Through Cortico-Hypothalamic pathway.
Corticohypothalamic centers
Thoracolumbar sympathetic cell bodies
Skin vessels.
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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.
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CUTANEOUS VASCULAR RESPONSE.
White reaction Triple response. Axon reflex. Reactive hyperemia. Cold vasodilatation. Cold vasoconstriction.
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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.
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TRIPLE RESPONSE. When skin stroke
more firmly with pointed objects
3 parts response occurs
Red reaction Flare Wheal
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Monday, May 1, 2023
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 controlLocal release of
Bradykinin.
Neural control Local release of histamine &
histamine like substances by mast
cells.
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).
Monday, May 1, 2023
DERMATOGRAPHIA Striking triple response
that occurs as an unusual reaction.
Anything drawn on skin causes.
Due to excessive release of Histamine.
Monday, May 1, 2023
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.
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COLD VASODILATATION. Exposure to Cold
Cutaneous vasoconstriction due to hypothalamic mechanism.
But prolonged & severe vasoconstriction – Frost bite.
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Monday, May 1, 2023
COLD VASOCONSTRICTION. Exposure to cold Cutaneous
vasoconstriction due to hypothalamic mechanism.
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Monday, May 1, 2023
Thank you.
Monday, May 1, 2023