Tissue: A group or layer of cells that perform specific functions. For example, muscle tissue is a group of muscle cells.issue: A group or layer of cells that perform specific functions. For example, muscle tissue is a group of muscle cells.
1 The skin is a barrier to the outside world protecting the body from infection, radiation, and extremes of temperature.  There are many types of wounds that can damage the skin including abrasions, lacerations, rupture injuries, punctures, and penetrating wounds.
The major types of secondary skin lesions are: 1  Ulcer. Lesion that involves loss of the upper portion of the skin (epidermis) and part of the lower portion (dermis). 2  Scale. A dry, horny build-up of dead skin cells that often flakes off the surface of the skin. 3  Crust. A dried collection of blood, serum, or pus.  Erosion.