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Skin-nontumor / Clinical Dermatology

General

Normal adnexae


Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC, Memorial University of Newfoundland (see Reviewers page)
Revised: 24 August 2011, last major update August 2010
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Micro description
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● Skin adnexa include hair follicles, sebaceous glands, eccrine sweat glands and apocrine glands

Follicular unit:

● Functional complex of terminal and vellus hair follicle, sebaceous gland, erector pili muscle and (depending on site) apocrine gland
● Often contains Demodex folliculorum mites, clumps of Staphylococcus epidermidis or Pityrosporum yeasts
● Each follicle has an epithelial and mesenchymal component
● Embryologically, the epithelial buds (hair germs) derive from the fetal epidermis and project downward, interacting with mesenchymal cells which form the dermal sheath and dermal papillae

Hair follicle:
● Contains protected repositories of epithelial stem cells
● Forms hair via cyclic process of (a) anagen or growing phase, (b) catagen or involuting phase and (c) telogen or resting phase
● Matrix (regenerative) cells line the dermal papillae, are mitotically active, give rise to hair shaft and inner root sheath

Outer root sheath:
● Layer of large cells that surround inner root sheath
● Undergo abrupt keratinization without a granular layer, at level of isthmus (mid hair follicle, extends to sebaceous duct), called trichilemmal keratinization
● Usual type of keratinization occurs by cells of infundibulum (upper hair follicle)

Acrotrichium:
● Intraepidermal portion of hair follicle

Sebaceous glands:

● Lobulated structures which develop as a lateral protrusion from the outer root sheath of hair follicles
● Have outer germinative cells that differentiate, move inward and accumulate intracytoplasmic lipid droplets, causing multivacuolation and multiple indentations of nuclei
● Excretory ducts of these glands empty into infundibulum of hair follicle

Sweat glands:

● Sweat glands are either eccrine (regulate body temperature), apocrine or mixed

Eccrine sweat glands:
● Tubular with secretory and excretory portions
● Secretory coil is in deep dermis or subcutis, has secretory and myoepithelial cells
● Excretory portion has dermal (straight) and intraepidermal (spiral, also called acrosyringium) portions

Apocrine glands:
● Concentrated in axilla, groin and perineum; also in face, external auditory meatus, eyelid and areola.
● Have secretory and excretory components
● The secretory portion has an outer discontinous layer of myoepithelial cells and an inner layer of cuboidal to columnar eosinophilic cells
● Decapitation secretion is conspicuous
● Secretory cells have abundant eosinophilic cytoplasm with lipid, iron or lipofuscin
● Positive for GCDFP-15 and CAM 5.2

Drawings
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Hair follicles

Sweat glands

Micro images
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Hair follicles


       

Sweat glands


   

Sebaceous glands

Positive stains
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Eccrine and apocrine glands: EMA, CEA, keratin, S100
Myoepithelial cells: actin, calponin, caldesmon, S100

End of Skin-nontumor / Clinical Dermatology > General > Normal adnexae


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