We’re all hairy. Hair covers almost all of our bodies, from the flowing locks on our heads to the delicate wisps on our arms and legs. Far from being purely cosmetic, mammalian hair evolved millions of years ago as protection from the cold – long before any cave-person thought of sticking a bone through it and going on the hunt for a date. Pictured, dyed blue and green, is a bed of tiny mouse hair follicles, the organs in mammalian skin from which hairs sprout. Arrector pili muscles (stained red and pink attached to the follicles) pull the hair upright in cold weather to produce ‘goose bumps’ – trapping a layer of air next to the skin for warmth. At the base of each follicle is a round blue structure called ‘the bulge’ where stem cells are nurtured before being released into the follicle to produce new, luxuriant, hair growth.
Written by John Ankers
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.