human anatomy lecture notes 4

Lucidum and s corneum but organized into layers

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Unformatted text preview: ed from invagination of the epidermis that push down into the dermis  ­ Terminate at the 'hair root' (epidermal) where dermal papilla indents to supply blood vessels and nerves to the area of the hair root  ­ The outer external root sheath of the hair follicle consists of a modified stratum basale and stratum spinosum (see above)  ­ The inner internal root sheath of the hair follicle consists of differentiating stratum granulosum ­ like cells that produce very ordered/regularly arranged cells that move inward and die to produce to the hair shaft (analagous to the s. lucidum and s. corneum but organized into layers = cuticle, cortex and medulla moving from outside in) ** Note:  ­ Arrector pili (smooth) muscle fibers anchor to the dermal connective tissue that surrounds hair follicles; responsible for generating 'raised hair' and 'goose bumps' (under involuntary autonomic control) Sebaceous Glands  ­ form as an out pouching of the hair follicle epidermis above hair bulb  ­ ducts may branch slightly and empty into hair canal (the small space between the fully formed hair shaft and follicular epithelium)  ­ alveolar secretory portion secretes lipid ­rich sebum that stains palely by H&E  ­ mode of secretion is by...
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