Page 481 - Atlas of Histology with Functional Correlations

FIGURE 12.5 | Section of Hair Follicle with

Surrounding Structures

This figure illustrates a longitudinal section of a hair follicle with surrounding
structures. The different layers of the hair follicle are identified on the right side.

The hair follicle is surrounded by an outer connective tissue sheath (15) of the
dermis (7) under which is the external root sheath (14) composed of several
cell layers. These cell layers are continuous with the epithelial layer of the

epidermis. The internal root sheath (13) is composed of a thin, pale epithelial
stratum (the Henle layer) and a thin, granular epithelial stratum (the Huxley
layer). These two cell layers become indistinguishable as their cells merge in the
hair bulb (21). Internal to the cell layers of the internal root sheath (13) are cells
that produce the cuticle (12) and the keratinized cortex (11) of the hair follicle,

which appears as a yellow layer. The hair root (16) and the dermal papilla (18)
form the hair bulb (21) where the external root sheath (14) and internal root
sheath (13) merge into the hair matrix (17), situated above the dermal papilla

(18). Cell mitoses and melanin pigment (19) produced by melanocytes are seen
in the matrix cells (17). Numerous capillaries (20) supply the connective tissue
of the dermal papilla (18).

In the connective tissue of the dermis (7) and adjacent to the hair follicle are
transverse sections of a coiled sweat gland (8, 9). The secretory cells (9) of the

sweat gland are tall, stain light, and their bases are surrounded by flattened
contractile myoepithelial cells (10). The excretory ducts (8) of the sweat gland
are smaller in diameter, are lined with a stratified cuboidal epithelium, and stain
darker than the secretory cells (9).

A sebaceous gland (4) connected to the hair follicle is sectioned through the
middle. This gland (4) is lined with a stratified epithelium that continues with the
external root sheath (14) of the hair follicle. The epithelium of the sebaceous
gland is modified, and along its base is a row of columnar or cuboidal cells, the
basal cells (3). These cells rest on a basement membrane, surrounded by the

connective tissue of the dermis (7). The basal cells (3) of the sebaceous gland (4)
divide and fill the acinus of the gland with larger, polyhedral secretory cells (5)
that enlarge, accumulate secretory material, and undergo degeneration (2). This

process produces the oily secretory product of the gland, called sebum. Sebum
passes through the short duct of the sebaceous gland (1) into the lumen of the
hair follicle.

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