Which is the largest organ in human body……….?

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Dr. Jitendra Patel (MBBS, MD, ACME, Ph.D…)

Medical Educator, Researcher & Academic Administrator

Associate Professor, Department of Physiology

Email: dr.jrpatel84@gmail.com Web: www.esphys.weebly.com2

Competency

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No. PY 5.10* (CV Physiology)

CompetencyDescribe and discuss cutaneouscirculation

D/L/Core K/KH/Y

AM Written/Viva voce

Integration No

Imp. Concept Triple response

Phy. Trivia Axon reflex

OUTLINE

Physiological anatomy

Characteristic features

Regulation & Factor affecting

Clinical

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Physiologic anatomy...cont

• Main function: Regulation of body temperature

• Blood flow;

Rest: 10-15 ml/min/100gm

Max: 150 ml/min/100gm

Min: 1 ml/min/100gm

(~500 ml/min)

• In microcirculation;

Arterioles, Meta-arterioles, pre capillary sphincters, Capillaries,

Venules

Characteristic features

Heat Exchange in the Skin

Regulation

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Neural factors:-

VC: sympathetic stimulation

Hypothalamic response to temperature variation

– A-V anastomosis

– Sweat glands, Bradykinin

VD: no partasympathatic vasodilator nerves

– Reduction in VC activity

– Local bradykinin in sweat glands

– Local VD metabolites

Factor affecting

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Exposure to cold: VC

Exposure to heat: VD

Exercise: Dual response

Emotional factors: (corticohypothalamis pathway)

Blanching (pale, in fear, VC)

Blushing (red, embarrassment, VD)

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General responses & Color changes in skin• Fiery red color in reactive hyperemia – Re establishment of

circulation after a period of occlusion, Hypoxia dilates

arterioles

• Gray /cold blue skin – Arterioles are constricted and

capillaries are dilated

• Warm, red skin – Both are dilated

• Rudy complexion in cold – VD

• Emotional factors via corticohypothalamic fibers produces

– Blanching of skin e.g. pale with fear

– Blushing by anger / embarrassment

Applied Term

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• White reaction:

(Constriction of pre-capillaries sphincter)

• Dermatographia:

(Striking triple response); Histamine

Applied Term

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• Reactive hyperaemia (e.g. BP, CC)

• Trench foot (VC to cold, ischemia)

• Frost bite (VD to extreme cold)

• Triple response (mIMP)

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Ruddy complexion

Trench foot

Frost bite

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Triple response

RFW

Skin stroked more firmly with pointed object

– Red reaction – redness at the site appears in

about 10 second.

– Flare –Wheal– local edema.

– redness spread out from injury.

Triple response

Triple response - mechanism• Red reaction

• Dilatation of precapillary sphincter due to direct response of

capillaries to pressure

• No role of nerves so no effect of anesthesia

• Flare

• Dilatation of arteriole, precapillary sphincters by axon reflex

• Increased local blood flow increases local temperature

• Abolished by local anesthesia

• Wheal

• Increased capillary permeability by histamine / sub.P

• Increased capillary pressure due to dilatation of precapillary sphincter

Axon reflex

Flare is due to antidromicconduction insensory nerve branches

Nerve fiber: type CNT:

Substance P & CGRP

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EXERCISE

A. SN: Triple response

B. SAQ (Trench foot Vs Frost bite) (NT released

in axon reflex) (full name of CGRP) (Axon

reflex)

C. Interactive question (mentimeter app)

D. MCQs (online – Google form)

Reference Reading

A. Indu khurna, G K Pal

B. Ganong

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VALUE HAS A VALUE ONLY IF ITS VALUES IS VALUED

- Unknown

Physiological TriviaPatients in shock should not be warmed to

the point that their body temperature rises. This is

sometimes a problem because well-meaning

laymen have read in first-aid books that “injured

patients should be kept warm,” and they pile

blankets on accident victims who are in

shock.......:P

# stay home stay healthy stay happy stay safe #

# fight against nCORONA#

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