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| The bulb of a follicle |
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| Parts of a follicle (intradermal part only) |
If you are missing the
granular layer, note that it continues only upto a little below the
acrotrichium (the intra-epidermal part of the follicle). To quote Lever
"In the middle portion of the hair follicle, the so-called isthmus, which extends upward from the attachment of the arrector pili muscle (so-called bulge region) to the entrance of the sebaceous duct, the outer root sheath is no longer covered by the inner root sheath, which by then has keratinized and disintegrated. The outer root sheath therefore undergoes keratinization. This type of keratinization, referred to as trichilemmal keratinization (141), produces large, homogeneous keratinized cells without the formation of keratohyaline granules. Trichilemmal keratinization is found also in catagen and telogen hairs and in trichilemmal cysts and trichilemmal tumors."
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