Hair Cycles (the inconstant portion)

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F1Ch10 (R4564): This is a section of the same follicle illustrated in Ch9 but at a slightly more superficial level (nearer the epidermis). A red arrow identifies the vitreous (glassy membrane - a thick, hyalinized basement membrane). The stratified clear cell layer (the outer root sheath) cannot be identified as having a locus of origin in one of the strata of the hair bulb; it appears to be a specialized layer as an extension of the non-matrical epithelium of the follicle. The granular zone apparently contributes the file of plate-like acidophilic cells (with pyknotic nuclei) that presses upon the granular layer. I assume that this row of cells represents Henle’s layer. Yellow arrows mark the interface between a file of dark cells and the file of pale cells on the inner surface of Huxley’s layer. A portion of the medulla of the hair shaft is represented near the top of the field. Also in the upper portion of the field, a hard cuticle is evident along the hair shaft in the region where the shaft has pulled away from the granular layer. At its point of origin  (in this field), the cuticle is intimately associated with the file of cuboidal dark cells. The file undergoes atrophy in this area. In the area of the blue arrow on the right (marking the interface between granular layer and stratified clear cells), a thin red line is represented; on this basis, I favor the interpretation that the file of pale acidophilic cells on the inner surface of the stratum of clear cells is an anatomic boundary, and that the adjacent file of pale acidophilic cells is a contribution from the granular layer. In the region of the separation between shaft and sheath, a column of pale acidophilic, (ghost) cells has accumulated; some of these cells have pyknotic nuclei They merge with the file of pale acidophilic cells.


F2Ch10: The features of the inner root sheath, as seen in Ch10P1, are somewhat better defined at a higher magnification. In areas, the pale cuboidal cells of the inner row (“cuticle” of the inner root sheath, in a file, are cytologically different from the cells of “Henle’s layer” on the outer surface of the inner root sheath. Thin, parallel, keratinized lamellae partition the population of elongated, thin cells in the hair shaft.


F3Ch10: Interfaces are defined with blue and green arrows. The yellow arrow points to a portion of the medulla. In the dynamics of cell growth in the outer root sheath, there has to be some provision for a free movement of cells along the surface of the Henle’s layer; I see Henle’s layer as a contribution from the population of keratinizing cells in Huxley’s layer. In this approach, the inner root sheath is a lamina that is sandwiched among the outer root sheath, and the “cuticle” of the hair shaft (as I interpret the patterns, the cuticle, at a deep level, is a row of viable cells; at a more superficial level, it is a row of keratinizing, anuclear, ghost cells; and beyond the separation between inner root sheath and hair shaft is truly a “cuticle”). At its deep extremity, the outer root sheath consists of only two layers, one of which is a basal layer that abuts upon the glassy membrane. In this field, on the left side of the follicle, the extremity of the outer root sheath is represented. The second generation cells are compressed against Henle’s layer with their nuclei directed obliquely upward. It is my interpretation that the cells that are contributed in this manner move upward along a surface. A population of cells, that has been contributed by the outer layer of the outer root sheath on one side, abuts upon the cellular component of Henle’s layer on the other side to form an interface. The upwardly migrating cells eventually keratinize and then are released into the lumen of the follicle above the area where the cuticle of the hair shaft has separated from the “cuticle” of the inner root sheath. In the act, the respective portion of the keratinized inner root sheath is also shed into the lumen. In this manner, the isthmus of the follicle comes to be defined as an anatomic unit.


F4Ch10: This follicle, in cross section, shows a central terminal hair. The hair shaft is buttressed by two or three layers of fully keratinized cells; these cells retain their cuboidal shape and are devoid of nuclei; this layer represents the contribution of Henle’s layer, Huxley’s layer, and the “cuticle” of the inner root sheath. The inner row of cells of the outer root sheath abuts upon the layer of keratinized cells. This inner row is composed of cuboidal and rectangular cells that have acidophilic cytoplasm and preserved nuclei; I would interpret these cells as keratinizing cells of the outer root sheath. Blue arrows mark the interface between the keratinizing cells of the outer root sheath, and the keratinizing cells that have been contributed by the inner root sheath.


F5Ch10: A small hair is represented in cross section. Blue arrows identify the interface between the outer root sheath and the keratinized cuticle derived from cells of the inner root sheath. Between the blue and red arrows, cells of the outer root sheath show evidence of keratinization (increased cytoplasmic acidophilic providing the evidence). On the right, the keratinizing cells of the outer root sheath have preserved nuclei. On the left side of the hair shaft, keratinizing cells of the outer root sheath are flattened and are devoid of nuclei; there are at least two layers of such cells. 


F6Ch10: In the zone in which the hair shaft separates from the cuticle of the inner root sheath, green arrows identify cells of the outer root sheath; these cells contain fine fibrils in the cytoplasm; the fibrils are perpendicular to the long axis of the hair shaft. These fibrils might be taken as evidence of early keratinization. In the area above the hair shaft, the blue arrows point to a file of flattened dark cells with pyknotic nuclei. The last arrow to the right, in this row of arrows, point to what appears to be the termination of this file of flattened cells. The cells of this file represent those that are commonly identified in photomicrographs as the cuticle of the hair shaft. The refractile well-defined membrane that extend to the right along the hair shaft properly qualifies as the cuticle of the cortex. At the point of termination, the flattened, dark cells overlap the cuticle. The single blue arrow below the hair shaft identifies a file of small, cuboidal cells with small nuclei and perinuclear vacuoles; these cells represent a component in a location that commonly is identified as the “cuticle” of the inner root sheath.

In chapters 33a, 34a, 34aa, 34b, & 34c, the follicle-like qualities of certain tumorous infections, or neoplasms are discussed; there is the opportunity to compare certain features of the tumorous processes with the anatomic features of normal follicles. The disorders include a fibrofollicular hamartoma, molluscum contagiosum, and pilomatrixoma.



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