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Grown feathers

basal part of the dermal papilla
apical part of the dermal papilla
inner pulp membrane
pulp caps
epidermal collar
outer pulp membrane
wall of the calamus
corneous layer of the follicular epidermis
germinative layer of the follicular epidermis
inner layer of the follicular dermis
outer layer of the follicular dermis
m. pennatus

Longitudinal section of the follicle and calamus of a grown contour feather of a chicken (HE): dermal papilla

In resting stage, the dermal papilla consists of a basal zone of rounded cells and an apical zone of flattened cells. The basal zone is continuous with the outer layer of the dermis of the follicle, the apical zone is continuous with the inner layer of the dermis of the follicle.

The dermal papilla, the epidermal covering of the dermal papilla and the epidermal collar (the transitional zone between epidermal covering of the dermal papilla and the epidermis of the follicular wall) constitute the feather blastema out of which a new feather will develop.