Arrector pili muscle: evidence of proximal attachment variant in terminal follicles of the scalp.
BACKGROUND
There is general agreement that the proximal attachment site of the arrector pili (AP) muscle, via elastic tendons, is the bulge region, where follicular stem cells are situated. A variant of this insertion, in which the AP muscle surrounds the follicle circumference, has been described in human facial vellus hair follicles.


OBJECTIVE
To investigate whether terminal hair follicles of the human scalp may also present this variant of proximal insertion of the AP muscle.


METHODS
Histological and immunohistochemical methods were used.


RESULTS
At the bulge level, bundles of the AP muscle were seen to encircle the entire hair follicle.


CONCLUSIONS
Terminal follicles of the human scalp may also present this variant of proximal insertion of the AP muscle.
Barcaui
Carlos Baptista
CB
Federal University of São Paulo, Rua Farme de Amoedo 106, Ipanema, Rio de Janeiro 22420-020, Brazil. baptista@ax.apc.org
Piñeiro-Maceira
J
J
de Avelar Alchorne
M M
MM
D018859:Hair Follicle / Q000033:anatomy & histology*; D006801:Humans; D007124:Immunoenzyme Techniques; D009130:Muscle, Smooth / Q000033:anatomy & histology*; D012535:Scalp / Q000033:anatomy & histology*