Skin - The Jack of all Trades — BIOLOGY STD 9 — Question

Vasodilation: Dilation of blood vessels in the skin leading to an increase in the blood supply.
Vasoconstriction: Narrowing of blood vessels leading to reduction in the blood supply to the skin.
Temperature regulation in cold weather:

1. At low temperature, the blood vessels get narrowed or vasoconstricted. This reduces the blood supply to the skin.
2. There is less loss of heat by convection, conduction and radiation. There is less loss of heat through vapourization as reduced blood supply lowers the secretion of sweat by sweat glands.

Temperature regulation in hot weather:

1. At high temperature, the blood supply to the skin is increased by vasodilation or dilation of blood vessels in the skin.
2. This results in greater loss of heat by convection, conduction and radiation.There is more loss of heat through vapourization as more sweat is secreted due to rich supply of blood to the skin.