Classification and pathophysiology of skin grafts.

Flaps and grafts are the 2 main surgical procedures to repair losses of skin tissue. A flap is a full-thickness portion of skin sectioned and isolated peripherally and in depth from the surrounding skin, except along one side, called the peduncle. A graft is a section of skin, of variable thickness and size, completely detached from its original site and moved to cover the zone to be repaired. According to their thickness, skin grafts are classified as split thickness (or partial) and full thickness. The former is further divided into thin, intermediate and thick. Split-thickness skin grafts usually take well, whereas a full-thickness graft only takes if it is relatively small. Grafts are also divided, on the basis of their origin, into the following: autografts, when the donor and recipient are the same individual; homografts, when the donor and recipient are different subjects belonging to the same species; hetero- or xenografts, when the donor and recipient belong to different species. Only autografts can take, whereas homo- and heterografts are rejected. Homo- and heterografts, however, can be useful in particular conditions, for example, extensive burns, because they temporarily ensure vital skin functions.