Limb bud

Limb bud

A limb bud is a structure present during embryonic development that eventually forms the limb of an organism. It is one of the fundamental aspects of developmental biology.

Structure

The limb bud consists of a core of mesoderm that is covered by a layer of ectoderm. The mesoderm within the limb bud begins to proliferate rapidly, while the ectoderm on the distal part of the limb bud thickens to form the apical ectodermal ridge (AER).

Development

The development of the limb bud is a complex process that involves a series of reciprocal interactions between the ectoderm and the underlying mesoderm. The AER plays a crucial role in the outgrowth of the limb bud by maintaining the underlying mesoderm in a proliferative state. This is achieved through the secretion of fibroblast growth factors (FGFs) by the AER.

Molecular basis of limb bud development

The development of the limb bud is regulated by several key genes and signaling pathways. These include the Sonic hedgehog (Shh) gene, which is expressed in the zone of polarizing activity (ZPA), and the Wnt and BMP signaling pathways.

Clinical significance

Abnormalities in limb bud development can lead to a variety of congenital limb defects, such as polydactyly (extra digits), syndactyly (fused digits), and limb reduction defects (absence of part or all of a limb).

See also

• Embryogenesis
• Organogenesis
• Morphogenesis

References

Limb bud Resources
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