The creation of feathers

Like hair and nails, feathers consist of keratin, which is produced by specialised cells in the epidermis. These keratinize and then die, leaving behind very strong keratin structures.

A sheath develops, and the feather begins to grow helically outward. Once growth is completed, the blood supply shuts down, while the feather breaks through the last layer of the epidermal sheath to unfold completely. It is now fully functional.