Hair Restoration with Follicular Unit Extraction (Part 3)

The best follicular unit extractions (FUE) come when the entire follicular unit, the bulb with the dermal papillae and the capsule are removed intact and there is no amputation/transection of hairs within the graft.

In theory, the more the follicular unit is stripped of its surrounding tissue, the lower the growth potential. If the outer root sheath (ORS) is not violated and some fat remains below the bulb, one can assume that the follicular unit was removed without damage. If the lower ends of the hairs of the excised follicular unit contain a glistening covering and the bulb is intact, then it can be assumed that the follicular unit came out wholly intact. If the outer root sheath is violated and stripped from its covering, one should expect some negative impact on the growth. This could result in a thinner, less robust hair from one or more of the hair follicles within the extracted follicular unit. In summary, the best preserved follicular unit is one where the ORS is intact, the hairs are covered with a glistening covering, there is fat at the bottom of the bulb where the dermal papilla is located, and there is no amputation/transection of the hairs within the graft.

The follicular unit is surrounded by a capsule that isolates the hairs from the surrounding dermis and fat. This capsule is called the outer root sheath (ORS) and extends to the surface of the skin to produce the pore the hair exists from. When we extract a follicular unit from the scalp using the strip harvesting method, for example, this outer root sheath is included in the graft. All of the vital structures of the follicular unit lie encased in this ORS.

At the bottom of the bulb of the hair, lies a structure called the dermal papillae (DP). The hair bulb looks like a catcher's mitt from the bottom, and the DP is the ball inside the mitt. The DP contains the master switch that controls the hair growth genetically. Cells inside the DP express the genetics that initiates the hair growth process and is integrally involved in the various stages of the hair cycle. In the photo below (at right), we see two hairs, one fully developed (terminal) hair and one small hair that is growing out of its telogen (resting) phase into its anagen (growth) phase, evolving into a mature terminal hair.

Note that the telogen hair produces a finer hair while the hair is growing. This hair will get thicker as the hair matures into its 'terminal' status. The bulb at the bottom of the telogen hair stands out prominently as it does in the mature terminal hair but the DP cannot be seen without special stains or equipment.

More information on FUE will follow in further articles, alternately visit our website to learn more about hair restoration .

by Dr S R Bassi