Pilosebaceous follicle

The pilosebaceous follicles are the target sites for acne. The pathophysiology of acne centers on interplay of follicular hyperkeratinization, increased sebum production, action of Propi-onibacterium acnes (P. acnes) within the follicle, and production of inflammation (Table 11.1). 

Keratinization and drying of the epidermis occur, and papular eruptions involving the pilosebaceous follicles may be found, especially on the extremities. 

Acne results from disordered function of the pilosebaceous follicle whereby abnormal keratin and sebum (the production of which is androgen driven), form debris which plugs the mouth of the follicle. Propionibacterium acnes colonises the debris. Bacterial action releases inflammatory fatty acids from the sebum. 

The pathogenesis of juxtaclavicular beaded lines is unclear. Some authors have reported a prevalence of 16% in heart transplant patients, but only in men. Becanse ciclosporin is highly lipophilic, it has many adverse effects associated with alterations of pilosebaceous follicles, snch as hypertrichosis and acne. In this case the authors postulated that the combined effect of prednisone and ciclosporin may have induced sebaceous gland hyperplasia. 

Acne itself is a disorder of the pilosebaceous follicles and these follicles as well as the adjacent skin surface are well populated with micro-organisms. Three micro-organisms have been implicated in 2icnc - Propionibacterium acnes, Staphylococci spp. and Pityrosporum ovale-With the former being the most important. However, micrococci, sarcina and yeasts are also present and a change in their population may predispose the patient to acne (Holland and Cunliffe, 1979). 

Fig. 2.10 Pilosebaceous follicle with arrector pUi muscle. Hematoxylin-phloxine-saffron stain. Obj x20...

The pilosebaceous unit of the skin consists of a hair follicle and the surrounding sebaceous glands. An initial acne lesion called a comedo forms when there is a blockage in the pilosebaceous unit.8... 

Liposomes applied on the skin were also investigated for their delivery proprieties to the pilosebaceous units [15,23 28]. The in vitro skin penetration behavior of carboxyfluorescein incorporated in multilamellar liposomes (phosphatidylcholine cholesterol phosphatidylser-ine) and in another four nonliposomal systems (HEPES pH 7.4 buffer 5% propylene glycol 10% ethanol and 0.05% sodium lauryl sulfate) was studied by Lieb et al. [25]. Using two fluorescent techniques the authors found a higher accumulation of the probe within skin follicles when delivered from liposomes [25], Further, in an interesting setup of in vitro and in vivo experiments in mice, Hoffman s group observed liposomal delivery of the active Lac-Z gene and its expression mostly in the hair follicles [26,28]. 

Demodicosis is thought to be caused by an over-infestation of the mite in the follicles and pilosebaceous glands of the eyelids. These parasites cause destruction of the epithelial and glandular tissue, producing follicular distension, hyperplasia, increased keratinization, and acute inflammation. Dead mites and keratinization may play a role in the stagnation of secretions, which adds to the overall disease process. No current studies adequately prove the minimum number of mites necessary to produce symptoms therefore their role in pathogenesis remains imclear. It has been postulated that Demodex... 

Acne vulgaris (acne) occurs when keratin plugs at the base of the pilosebaceous oil glands near the hair follicles become inflamed resulting in papules, nodules, and cysts on the face, neck, shoulders, and back. 

Acne vulgaris is the result of several factors combined. The condition arises in the pilosebaceous units in the dermis, which consist of a hair follicle and associated sebaceous gland. These glands secrete sebum, a mixture of fats and waxes that protect the skin and hair by retarding water loss and forming a barrier against external agents. The hair follicle is lined with epithelial cells that become keratinised as they mature. 

Hair follicles and their associated sebaceous glands (pilosebaceous glands), eccrine glands, apocrine glands, and finger and toenails are all considered skin appendages. Hair follicles are found everywhere within the skin except for the soles of the feet, the palms of the hand, the red portion (vermilion border) of the lips, and the external genitalia. All are formed from fetal epidermal cells. Hair differs markedly in its prominence from place to place over the body. Delicate primary hair is found on the fetus secondary hair or down covers the adult forehead terminal hair ordinarily blankets the scalp and is found as pubic... 

Acne vulgaris is a disease of the pilosebaceous unit (i.e., the sebaceous glands and adjacent hair follicle). 

Acne vulgaris is a disease of the pilosebaceous unit (i.e., the sebaceous gland and adjacent hair follicle). Sebaceous glands, predominant on the face, chest, and upper back, respond to androgen stimulation. These glands provide sebum to the follicular canal and eventually to the skin surface through the foUicular opening (the pore). Follicular canal contents inclnde keratinocytes, Propionibacterium acnes (P. acnes), and free fatty acids. 

Pilosebaceous—Sebaceous gland and adjacent hair follicle. 

Figure 1-5. Pilosebaceous unit illustrating a hair follicle with its fiber and the different zones of growth and structural organization as the fiber emerges through the scalp. Reproduced with permission of Academic Press, Inc.

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