Microscopic vessels with walls no thicker than single cells, capillaries often burst, spilling their contents. Your body, although lacking flood insurance, responds routinely and effectively.
Broken Capillaries
Many minute ruptures occur daily in capillaries, note Sue Huether, Ph.D. and Kathryn McCance, Ph.D.
Hemostasis
Normally, your body repairs these ruptures through hemostasis, a process by which platelets and other factors seal breakages in vessels, observes the book "Human Physiology."
Contusions
Sometimes capillaries rupture due to blows that squeeze or crush soft tissues without breaking skin, producing bruises (contusions), according to the book "Understanding Pathophysiology."
Deeper Injuries
If confined to structures underneath the skin, bruising may produce no visible sign, note Sue Huether, Ph.D. and Kathryn McCance, Ph.D.
Discoloration
Nearer the skin's surface, capillary breakage appears red-purple in color, reflecting leakage of red blood cells, then as blue-black, and still later as yellow-brown or green as iron from destroyed red blood cells accumulates in the affected tissue, according to the book "Understanding Pathophysiology."
Purpuras
In cases of low platelet counts, hemostasis may fail to plug capillary breakages, resulting in small hemorrhagic areas (purpuras) under the skin and throughout the tissues, note Sue Huether, Ph.D. and Kathryn McCance, Ph.D.
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