Structural and ultrastructural comparison of hair and feather follicles

Formations of feather and hair follicles during embryonic stage are nearly similar. The aim of the present research is to study the similarities and differences between these two follicles in adult pigeons and rats. To fulfill this task, feather and hair follicles were dissected and processed for light and electron microscopy. The results demonstrated that these two follicles were similar in having dermal papilla and epidermal matrix. Moreover, the production of feather fibers and hair in them, respectively, is almost similar. However, unlike the hair follicle, the feather follicle has a distinct compartment, called the pulp at the top of the papilla. At the center of this pulp and dermal papilla a blood vessel exists, a character never observed in the hair follicle. Another difference between the two related to the thickness of the basement membrane exists at the interface between the papilla and epidermal matrix which in feather follicle is much thicker than its hair equivalent. In addition, at the base of feather follicle there is a distinct population of stem-like cells which could not be distinguished in the hair follicle. Based on the results obtained in this study, it seems that the feathers in birds and the hairs in mammals have been adapted for different biological tasks.