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Question 310
Physiology → Haematology
Classification
Question
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Two otherwise identical superficial wounds are compared. One is kept warm and dependent, whereas the other is elevated. Which combination best explains the expected difference in bleeding?
Question Stem
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Options
A
Warmth causes vasoconstriction while elevation raises intravascular pressure
B
Warmth activates factor XIII while elevation inhibits thrombin
C
Warmth lowers platelet count while elevation increases fibrinogen
D
Warmth causes vasodilation while elevation reduces intravascular pressure
E
Warmth inhibits the intrinsic pathway while elevation activates factor XII
Explanation
warm skin bleeds more because of vasodilation. Elevation reduces bleeding by reducing intravascular pressure. These are vascular and pressure effects rather than changes in coagulation-factor activation.
Option Validity
A) warmth produces vasodilation, not vasoconstriction. Elevation reduces rather than raises intravascular pressure.
B) Factor XIII stabilises fibrin and thrombin converts fibrinogen to fibrin, but these are not the mechanisms used by to explain the effects of warmth and elevation.
C) does not explain these observations through changes in platelet count or fibrinogen. It attributes them to vasodilation and intravascular pressure.
E) The intrinsic pathway begins with collagen and factor XII, but does not connect this pathway to the effects of skin temperature or limb elevation.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Initial Blood Loss, p.71.