Skin graft

A skin graft is skin taken from one place on the body and put on another, to cover a wound that is not going to close on its own. There are two ways to take it. A split-thickness graft carries the epidermis .. the top layer .. and part of the dermis, the layer underneath. A full-thickness graft carries the whole dermis.

And here is what almost no one imagines: that piece of skin arrives with no vessels of its own. It is not like a flap, which travels with its circulation attached. The graft sits on the wound, depending entirely on what the bed of that wound passes to it. It is like laying a cutting on damp soil: until it puts down roots of its own, all it receives is what the soil passes to it by contact. For the first few days the graft only absorbs, passively, the oxygen and nutrients that reach it by contact. That is called imbibition.

At around 48 hours the capillaries on the undersurface of the graft link up with the vessels of the wound: this is inosculation. By about the seventh day new vessels grow in, and that is neovascularization.

Each type has its advantage. The site a split-thickness graft was taken from heals over with new skin in two or three weeks. The full-thickness graft contracts less.