9thorough understanding of the anatomical layers is important, particularly when rotation and advancement flaps are planned. In these cases, dissection should be performed within the loose areolar tissue layer to preserve the pericranium, in case skin grafting of the flap donor site is needed.Blood vessels, lymphatics, and sensory nerves are found within the subcutaneous layer, superficial to the galea aponeurotica. Blood vessels that supply the scalp and forehead include the paired supratrochlear, supraorbital, superficial temporal, posterior auricular, and occipital arteries and their accompanying veins ( Fig. 9.1a). The supratrochlear and supraorbital arteries arise from the ophthalmic artery, a branch of the internal carotid artery. The remaining arteries that supply the scalp originate from the external carotid artery. These blood vessels are the basis for axial flaps used in local flap reconstruction of scalp defects. Robust interconnections between vascular territories allow for relatively long and large flaps to be used reliably. Caudal to the nuchal line, blood vessels that perforate the trapezius and splenius capitis muscles supply the skin of the posterior scalp and nape of neck.Sensory nerves of the scalp are also paired and include the supratrochlear (V 1 ), supraorbital (V 1 ), zygomaticotemporal (V 2 ), auriculotemporal (V 3 ), lesser occipital (C2, C3), and greater occipital (C2) nerves (Fig. 9.1b). The supraorbital and supratrochlear nerves supply the forehead and frontoparietal scalp. The zygomaticotemporal nerve supplies the region lateral to the brow and the temporal scalp up to the temporal crest. The auriculotemporal nerve supplies the lateral scalp, and the greater and lesser occipital nerves supply the occipital region.Motor nerves in the scalp innervate the muscles of this region, which include the frontalis, temporalis, auricularis (anterior, superior, and posterior), and occipitalis muscles. Of these, the most clinically significant is the temporal branch of the facial nerve, which supplies the frontalis muscle. This branch is located on the deep surface of the temporoparietal fascia and