Quick Facts
The epithelial portion of the hair follicle is divided into the inner root sheath and the outer root sheath. The inner root sheath has three layers: Huxley layer, Henle layer, and the cuticle of the root sheath. The outer root sheath does not have distinct layers and merges with the epidermis near the skin surface (Dorland, 2011).
Structure/Morphology
The internal root sheath is a layer composed of lightly keratinized cells which envelops the lower portion of the hair shaft, it does not extend past the isthmus (the middle segment) of the hair follicle. This layer and the external root sheath are produced by the rapidly reproducing matrix cells found in the periphery of the follicular bulb. The inner root sheath is composed of three concentric layers (from inside to outside), including the cuticle, Huxley’s layer, and Henle’s layer (Standring, 2016; Martini, Nath and Bartholomew, 2017; Joshi, 2011).
Function
The inner root sheath forms a tough outer sleeve for the hair, its rigid form protects the hair shaft as it grows.
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Joshi, R. S. (2011) 'The Inner Root Sheath and the Men Associated with it Eponymically', Int J Trichology, 3(1), pp. 57-62.
Martini, F. H., Nath, J. L. and Bartholomew, E. F. (2017) Fundamentals of Anatomy & Physiology. Pearson Education.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series: Elsevier Limited.
