Elizabeth Martin and Robert Hine. Latest Edition (7 ed.) Fully revised and updated, the sixth edition of this dictionary provides comprehensive coverage of biology, biophysics, and biochemistry, as well as key terms from medicine and palaeontology.
For example, if someone scratches a mole until it bleeds, the resulting lesion, a crust, is now a secondary skin lesion. The most common secondary skin lesions include: 1  crust: a crust, or a scab, is created when dried blood forms over a scratched and irritated skin lesion. 2  ulcer: typically caused by a bacterial infection or physical trauma. 3  scale: patches of skin cells that build up and then fall off the skin.
If you've ever wondered how scabs form, it is important to first understand what it is and why it happens. Scabs is an unattractive name for an unseemly body function that, however, serves an important purpose. When we fall, scrape or otherwise injure our bodies in a way that causes bleeding, it is the formation of scabs that promotes healing and keeps wounds from becoming infected.