Answer:
Skin graft take occurs in 3 phases: serum imbibition (24-48hrs), inosculation, and capillary ingrowth. Imbibition is the nourishment of a graft before the establishment of new vascular and lymphatic channels via “plasmatic circulation.” Its existence is supported by animal studies in which skin grafts gained weight in the first 20 hours through fluid absorption. Biochemical studies indicate an increase in water content during the first 5 days and a dermis rich in extracellular macromolecules capable of absorbing water and cations from the recipient site. Vital microscopy in rabbit skin grafts to the ear shows immediate graft edema. Studies of the color of skin grafts show a faint pinkish hue as early as a few hours after grafting. The edema in the graft may relate to biochemical processes within the graft similar to inflammatory edema.
Despite histologic, histochemical, injection suspension, tissue chamber, microangiographic and vital microscopy studies, there are conflicting theories regarding revascularization of skin grafts. The first is that circulation is restored in the original skin graft vessels via anastomoses between the recipient bed and the skin graft. This is supported by india ink staining studies showing ink in the graft vessels by the second day. The definitive blood vessels are those originally present within the graft. Alternatively, grafts may be perfused by new vessels that branch from the recipient bed into the graft. Enzyme studies of markers for viable endothelium show degeneration within the first 4 days and then a return of activity, suggesting definitive vasculature stemmed from ingrowth from the host bed. The present interpretation is that early filling of the graft endothelial spaces with serum-like fluid and erythrocytes occurs as a result of anastomosis of graft vessels with host vessels, coupled with early ingrowth and penetration of host endothelium.