hair follicle (folliculus pili)

Introduction

A tubelike invagination of the epidermis from which a hair develops. Hair follicles are lined by a cellular inner & outer root sheath of epidermal origin, a fibrous sheath is derived from the dermis. Sebaceous glands open into hair follicles.

The inner root sheath consists of 3 layers

• • cuticle
  • Henle layer
  • Huxley layer

Several cytokeratins are expressed specifically in layers of the inner root sheath.

The hair companion layer is a single layered band of flat & vertically oriented cells between the cuboidal outer root sheath cells & the inner root sheath that stretches from the lowermost bulb region to the isthmus of the follicle.

Several cytokeratins are expressed specifically in the hair companion laye.

More general terms

• follicle
• skin appendage

Additional terms

• hair
• hair follicle stimulation
• sebaceous gland