Chapter 16, Problem 1DQ

Summary Introduction

To review:

The mechanism of avian feather formation. Also explain the factor that patterns the placement of the feather bud placodes.

Introduction:

In avian species, feather formation begins from the feather follicles. Feather follicles are the invaginations starts in the epidermis down to the dermis. Dermis is the region where the follicle and pulp cavity starts to form the feather. Cell proliferation leads to the growth of feather filament, out of the follicle. Two different tissues are formed from the new cells, one is the sheath that surrounds the feather and second is pulp cap which protect the dermal core. Along the cell growth, spa the develops continuous and followed by the formation of calamus which is the quill of the feather.

Explanation of Solution

Epidermal placode is the first morphological manifestation of the embryonic feather of avian, which is a circular cluster of columnar ectodermal cells. After the placode formation, a dermal condensation is takes place beneath the epidermal placode. The outgrowth of the epidermal placode leads to the formation of feather bud and filament. This process is accompanied by the resumption of epidermal and dermal cell proliferation. Specific morphogenetic and proliferative events organize the discrete populations of epidermal cells and lead patterns in feather tracts. Periodic patterning within the tracts leads the division of originally homogeneous field into feather bud and interbud regions. This patterning is regulated by the expression pattern of several genes. Wnt-7a, β-catenin, L-Fringe, and NCAM are few genes which show the restrictive expression those progresses to the bud domain. The arrangement of the feather is shows a repeated hexagonal pattern on the avian body surface. Feather periodic patterning is regulated by a number of molecules that promote (activators) and suppress (inhibitors) feather bud formation. Fibroblast growth factors, such as FGF2 acts as activators and BMPs are known as inhibitors.

Conclusion

Thus it is concluded that formation begins from the feather follicles. Feather follicles are the invaginations starts in the epidermis down to the dermis. Periodic patterning within the tracts leads the division of originally homogeneous field into feather bud and interbud regions. This patterning is regulated by the expression pattern of several genes.