part of part_of part of part_of develops_from develops from pectoral appendage bud ectoderm apical ectodermal ridge pectoral appendage bud pectoral appendage apical ectodermal ridge AER forelimb An apical ectodermal ridge that is part of a pectoral appendage bud. An ectodermal thickening at the end of the forelimb bud in the developing embryo. [TFD][VHOG] Apical ectodermal ridge that is part of the pectoral fin bud.[TAO] EFO:0003487 EHDAA2:0000138 EMAPA:16778 Pectoral and pelvic fins are homologous to the tetrapod fore and hindlimb, respectively. (...) The zebrafish AER [apical ectodermal ridge] is an apical ectodermal thickening at the distal tip of the fin bud and consists of wedge-shaped cells of the basal stratum. The AER is observed only transiently, and from 36 hpf onwards the cells of this region form the apical fold (AF), which consists of a dorsal and a ventral layer of cylindrically-shaped ectodermal cells extending from the anterior to the posterior fin margin. Despite the change in shape, the AF still carries out the same functions as the AER. Indeed, although the AER receives its name from its characteristic shape, being composed of a pseudostratified ectoderm in the chicken and a polystratified ectoderm in the mouse, this independence of AER morphology from its function is also observed in tetrapods. The AF also expresses similar molecular markers to the tetrapod AER, suggesting that it fulfills similar functions in the fin as the AER does in tetrapod limbs.[well established][VHOG] TAO:0000085 TAO:0000736 UBERON:0005421 VHOG:0001064 ZFA:0000085 aer pectoral fin apical ectodermal ridge forelimb apical ectodermal ridge pectoral fin apical ectodermal ridge pectoral fin bud apical fold pectoral fin uberon upper limb bud apical ectodermal ridge wing AER wing apical ectodermal ridge