Limb patterning involves the establishment of three primary axes: proximal-distal, anterior-posterior, and dorsal-ventral. The proximal-distal axis is regulated by the AER through the secretion of FGFs. The anterior-posterior axis is controlled by the ZPA via Shh signaling. The dorsal-ventral axis is patterned by the ectoderm, particularly through the action of Wnt7a and Lmx1b.
