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RO The dermal papilla is the follicle’s instruction set, not part of the hair. It is a small cluster of specialised cells sitting in a cup at the base of the bulb, wrapped in blood vessels. It does not become hair. It tells the surrounding cells what kind of hair to build and for how long.
Its size sets the calibre of the shaft. A larger papilla drives a thicker hair; as it shrinks, the shaft it produces gets finer. This is the physical event underneath miniaturization — the visible thinning of a hair is the downstream result of a papilla that has become smaller.
It is also where the follicle listens for androgens. Androgen receptors in papilla cells are why one follicle responds to circulating hormone and its neighbour, a few centimetres away on the same head, does not. That regional difference is the entire reason a hair transplant works: a follicle carries its papilla with it, and with it the behaviour of where it came from.
It survives between cycles. When a hair is shed at the end of telogen, the papilla stays and is reused to build the next one. A graft that arrives with its papilla intact can grow; one whose bulb was cut through in extraction has lost the part that would have rebuilt it.
Related terms
For how follicles are moved without damaging this structure, see the FUE technique. For treatments aimed at the follicle itself, see PRP.
