There are 2 sets of arteries supplying the abdominal skin flap of the rat.The medial set consists of the medial branch of the lateral thoracic artery,the superficial epigastric artery and the perforating arteries and the lateral set is composed of the lateral branch of the lateral thoracic artery,the superficial circumflex iliac artery and the branches of the lumbar arteries.The former supplies the medial 2 thirds and the latter the lateral third of the abdominal wall.There is no significant difference in the number of vessels and the area fraction between the medial and lateral anastomotic areas.The abdominal skin flap of the rat is thinner than the human one and contain a little amount of fat and a layer of panniculus carnosus.The vascula-ture of the abdominal skin flap can be divided into 5 layers,that is,the superficial fascial,the pannicular carnosal,the profound dermal,the subpapillary and the papillary layers,which is similar to the vasculature of the human abdominal flap.But in the rat,there is no arterial anastomosis in the reticular layer of the dermis of the abdominal flap,which might be relatded to the insufficient thickness of the flap of the rat.