Medical Definition of Hair follicle

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Reviewed on 12/12/2018

Hair follicle: A sac from which a hair grows and into which the sebaceous (oil) glands open. The follicle is lined by cells derived from the epidermal (outside) layer of the skin.

Each follicle normally goes through a five-year cycle of growth and rest, with about 90% of the follicles growing hair at any one time, averaging about six inches (15 cm) of growth per year. Derived from the Latin word follis, for bag.

Skin illustration - Hair follicle

"The human hair follicle is a dynamic structure that generates hair through a complex and exquisitely regulated cycle of growth and remodelling governed by numerous genes," Siobhán A. Jordan has noted in Molecular Medicine Today.

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Reviewed on 12/12/2018