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RO Donor dominance is the principle the whole procedure rests on: a follicle keeps the characteristics of the site it came from, not the site it is moved to. Hair taken from the resistant band continues to resist the same hormonal signal after transplantation, which is why transplanted hair persists in an area where the original hair did not (Orentreich, Annals of the New York Academy of Sciences, 1959).
Where the zone sits. The resistant hair occupies a band across the occipital and parietal scalp — the back and the sides of the head. Its edges are not a drawn line. The boundary is a gradient, it differs between patients, and it moves as the pattern advances with age.
It is not uniform. Density, hairs per follicular unit and shaft calibre all vary within the band:
| Part of the band | What it typically offers |
|---|---|
| Mid-occipital | The richest and most reliable region |
| Parietal (sides) | Usable, but density and calibre fall toward the temples |
| Upper and lower margins | Least reliable — the hair here may thin later |
This is why extraction is distributed across the band rather than concentrated in the easiest part of it.
It is finite. An extraction point does not grow a new follicle. Hair is moved, not created, and the donor area is the total supply available for every procedure a patient will ever have. Planning is an arithmetic problem before it is an aesthetic one.
Related terms
For how the donor area is assessed, harvested and protected, see the donor area guide. For the extraction itself, see the FUE technique.
