[Sequence of development of cutaneous innervation of the limbs in the human embryo]

From stage 13 onwards, exploratory buds with a characteristic cellular cap may be observed in the limb buds. When the fibres become anchored to the corium, organogenesis is completed, but not maturation. The sequence of the cutaneous innervation of the limbs follows the proximo-distal development of the external forms, with a delay of 1 to 2 stages. The innervation of the upper limb segments usually precede that of the lower limb segments by one stage, moreover the innervation of the dorsal skin occurs slightly later than that of the ventral aspect of the limb. At stage 23, the exploratory buds have finished their progression in the fingers, and nearly so in the toes, but the anchored fibres do not pass the ventral aspect of the distal interphalangeal joints of the fingers, and have barely passed the proximal interphalangeal joints of the toes.