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.
Not all wounds bleed. For example, burns, some puncture wounds, and pressure sores don't bleed. Once the scab forms, your body's immune system kicks in to protect the wound from infection. 1  The wound becomes slightly swollen, red or pink, and tender.  You also may see some clear fluid oozing from the wound. This fluid helps clean the area.