The inner or epidermic coat of the

hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...

is closely adherent to the root of the

hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...

, and consists of two strata named respectively the outer and inner root sheaths.

Outer root sheath

The outer root sheath corresponds with the stratum mucosum (

stratum germinativum The ''stratum basale'' (basal layer, sometimes referred to as ''stratum germinativum'') is the deepest layer of the five layers of the epidermis, the external covering of skin in mammals. The ''stratum basale'' is a single layer of columnar or ...

and

stratum spinosum The stratum spinosum (or spinous layer/prickle cell layer) is a layer of the epidermis found between the stratum granulosum and stratum basale. This layer is composed of polyhedral keratinocytes. These are joined with desmosomes. Their spiny (Latin ...

) of the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

, and resembles it in the rounded form and soft character of its cells; at the bottom of the

these cells become continuous with those of the root of the hair.

Inner root sheath

The inner root sheath (IRS) consists of # a delicate

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

next the hair, composed of a single layer of imbricated scales with atrophied nuclei; #

Huxley's layer Huxley's layer is the second layer of the inner root sheath of the hair and consists of one or two layers of horny, flattened, nucleated cells. It lies between Henle's layer and the cuticle. The layer is named after English biologist Thomas Henry ...

Henle's layer Henle's layer is the third and the outermost layer of the inner root sheath of the hair follicle, consisting of a single layer of cubical cells with clear flattened nuclei. It is named after German physician, pathologist and anatomist A ...

The term "trichilemmal" refers to the outer root sheath. The IRS functions to mould, adhere, as well as participate in the keratinization of growing hair.

References

External links

* * {{Integumentary system Hair anatomy