Arrector Pili Muscle (APM)

Arrector Pili Muscle (APM)

The arrector pili muscle (APM) is not as well known as other muscles like the biceps, triceps or quadriceps. The APM is a small muscle attached to every hair. When it contracts, the result is goose pimples! It has been thought that the APM does not have any active role in any of the various mechanisms of hair loss and more or less acts as a ‘bystander.’ In new model of how balding develops, Australian dermatologist Rodney Sinclair and colleagues propose a model for understanding androgenetic alopecia. They propose that the APM has a key role in the decision of a hair follicle to ultimately "miniaturize" or get skinnier during the course of AGA.

By observing how miniaturization occurs within follicular units – the authors propose that by maintaining attachment to the APM, some hair follicles are prevented from proceeding down the pathway of permanent miniaturization.

Like all models, this proposal sets the stage for further exploration. The APM has perhaps been ignored for too long and may have a more important role than we ever imagined.

Reference
Sinclair R, Torkamani N and Jones L. Androgenetic alopecia: new insights into the pathogenesis and mechanisms of hair loss. F1000Res. 2015 Aug 19;4 (F1000 Faculty Rev):585