![](\"..\/wp-content\/uploads\/2019\/05\/Limb-bud-2.jpg\")
<\/div>\n<\/div>\nThe initial mesenchymal outgrowth of tissue from the flank of an embryo covered in ectoderm, which will go on to form fore and hind limbs. Becomes evident by about four weeks after conception as a result of complex interactions between the ectoderm and the underlying mesoderm (see figure below). Hox genes determine at which point along the axis of the embryo that the limb buds will form. The mesenchymal cells, which determine what type of limb will form, stimulate the formation of the apical ectodermal ridge.<\/p>\n<\/p>\n
<\/div>\n<\/div>\n
\n<\/p>\n
Human embryo at 4-5 weeks after conception, 5-7 mm. Upper limb bud circled in blue, lower limb bud in red. <\/p>\n
See Apical ectodermal ridge (AER)<\/a>, Dorsal plate in limb bud<\/a>, Ectoderm<\/a>, Embryo<\/a>, Embryogenesis<\/a>, Hox genes<\/a>, Mesenchyme<\/a>, Mesoderm<\/a>, Morphogenetic field<\/a>, Progress zone<\/a>, Ventral plate in limb bud <\/p>\n <\/p>\n <\/p>\n <\/body><\/html><\/p>\n","protected":false},"excerpt":{"rendered":" The initial mesenchymal outgrowth of tissue from the flank of an embryo covered in ectoderm, which will go on to form fore and hind limbs. Becomes evident by about four weeks after conception as a result of complex interactions between the ectoderm and the underlying mesoderm (see figure below). Hox genes determine at which point … <\/p>\n