How does hair continue to grow immediately after being transplanted?

[washingtondc]

I had an FUT done a little over two weeks ago, and looking at the transplanted grafts yesterday, many/most seemed slightly longer than they were when they were first implanted (though I could be wrong).

I'm curious if anyone knows how this happens? From what I thought, hair only grows during the anagen phase, which requires the follicle to be connected to the blood supply. Once the hair is disconnected from the blood supply (catagen phase) it transitions to its period of rest (telogen phase) for about 100 days, and then falls out (exogen) before restarting growth.

So how is it that transplanted hairs continue growing for a time after they've been removed from their location in the scalp and blood supply and transplanted into a completely new location? It would seem like removing them from their source would be equivalent to pushing them into catagen, and they'd stop growing. If they're still growing immediately post-transplant, that would indicate they're still in anagen. Does that imply that hairs that continue to grow after transplantation might remain in anagen and not fall out? I'm expecting all of mine to fall out, just curious if anyone who knows more than I do might offer some insight.

[MachoVato]

When the bulbs create a new hair, the old implanted hair gets pushed out. Expect lots of them to fall out once the shedding starts.

That said, some hair does just start growing right away.

[deeznuts]

I thought the trauma was what made them fall out but sometimes the hair survives the trauma?

[washingtondc]

19 hours ago, deeznuts said:

I thought the trauma was what made them fall out but sometimes the hair survives the trauma?

I thought that too. I thought the trauma/removal from blood supply when the follicle is extracted pushed the hair into the telogen phase, and then it falls out within a few months as it shifts to exogen. But if the hair continues growing after it's in the recipient site, that would seem to indicate it's still in anagen? So then what pushes it into telogen/exogen causing it to fall out if it's still in anagen for some time after being in the recipient area?

Anyone who knows more have any perspective on this?

[gillenator]

Although it is indeed trauma that causes the hair follicle(s) to enter the resting phase, sometimes this does not occur right away....yes, the transplanted follicle(s) can remain in the growth phase for an undetermined amount of time but sooner or later it will retreat and rest...some of the existing native hair is also impacted by trauma and will retreat into a resting period...this is evidenced as shock loss.

Regardless, whether it's related to trauma or just the normal cyclical behavior, all hair follicles move between the 3 phases of growth, rest, and shed.