Frostbite Occurs When Ice Crystals Form in the Tissues of the Extremities

In extremely cold conditions, when the extremities are vasυ- Constricted to conserve heat, the tissues may cool below the freezing point of tissue water. Ice crystals disrupt the tissue integrity, and gangrene can result. Normally, frostbite is pre­vented because vascular smooth muscle dilates in extreme cold, causing an inflow of warm blood. This mechanism apparently works adequately in animals that winter outdoors in northern climates.