Understanding Cutaneous Circulation and Blood Supply in Different Body Regions
Cutaneous circulation plays a vital role in supplying blood to the skin, with variations in apical and non-apical regions of the body. The blood flow is regulated by neural, thermal, and metabolic factors, and controlled by sympathetic fibers. Sympathetic vasoconstriction and vasodilation affect the skin's blood vessels. Thermal regulation is mainly influenced by body temperature, while the hypothalamus serves as the temperature regulation center. Metabolic regulation is less significant in cutaneous blood flow.
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Cutaneous circulation Dr Pushpa Lata Sachan Associate professor C I M S & H ,Lucknow
Functional anatomy Blood supply of the skin of apical regions ( Fingers, feet , toes ,palm, nose lip ,ear lobes etc.) is different from non apical regions (the body tarso) of the body . Apical areas an arteriolar network exist at the boundaryof dermis and subcutaneous tissue .
From this network arterioles ascend from deep dermis to superficial layer of dermis . Capillary loops originate from superficial dermal network and perfuse the dermal papilla and epidermis . Non apical areas here vascular pattern is modified . Arteriovenous anastomoses mainly occur in superficial dermal tissue. It Is very few or absent in non apical areas
Normal blood flow to the skin varies from 1 to 150 ml per 100g of tissue per min . The skin blood vessel are supplied by sympathetic fibers . No parasympathetic innervation is seen in the skin . Activation of sympathetic vasoconstriction . Vasodilation occurs by decreasing the sympathetic activity . fibers results in
Regulation of cutaneous blood flow Is regulated by decreasing the sympatheticactivity . Cutaneous blood flow is regulated by neural ,thermal and metabolic factors . Neural regulation cutaneous supplied by sympatheticvasoconstrictorfibers . There is no vasodilator system supplying the skin blood vessels . blood vessels are
Thermal regulation Thermal regulation cutaneous blood flow is mainly regulated by body temperature . Increased body temperature causes vasodilationand decreased body temperature causes vasoconstriction .
HYPOTHALAMIC CONTROL MECHANISM Temperature Regulation centre of Hypothalamus
Metabolic regulation Is not important for cutaneous circulaton . Local production of bradykinin in the sweat causes cutaneous vasodilation .
Applied physiology Vascular response to injury White response Triple response White response Skin is stroked lightly with pointed object , stroke line become pale this is called as white reaction . This occur due to decreased blood flow in the capillaries due to contraction of precapillary sphincter in response to injury . The response is observed in about 15 second .
Triple response When the skin is stroked with pointed object -the response to injury manifest as triple response . This is called as triple response as it three component red , wheal and flare . Red reaction the skin becomes red in about 10 seconds .Redness occur due to capillary dilation that increases capillary blood flow .Capillary dilation occur due to direct response of capillaries to pressure .
Wheal swelling is called wheal .This occur within few minutes following red reaction. It occur due to increased permeability of capillaries and post capillary venules . Histamine released from local mast cells causes vasodilation and increases capillary permeability that result in extravasation of fluid .
Flare - Spreading out of redness from the site of injury to surrounding area is called as flare . It occur due to arteriolar dilation . arteriolar dilation occur by activation of axon reflex . From the site of injury impulse is conducted in the afferent fiber . Sensory neuron give branches to blood vessel .
The impulse in addition to its conduction to the spinal cord orthodomically, it also relayed antidromically to blood vessels Axon reflex is an example of antidromic conduction of impulse. The ending of sensory fibers on the blood vessels release substance P and CGRP that produce arteriolar dilation . Redness spreads out from injury to surrounding skin in the form of flare .
Reactive hyperemia This is defined as increased blood flow in an area when blood supply to the area is reestablished following a brief period of occlusion . The blood flow to the skin increase when the circulation is reestablish after the short period of occlusion.
Reactive hyperemia also occur in visceral organs . It occur due to vasodilation produced by hypoxia during occlusion . When circulation reestablished blood flow increases through dilated blood vessels and skin becomes red
