Dermal papilla

Kaufmann H et al. Influence of low temperature on productivity, proteome and protein phosphorylation of CHO cells. Biotechnol Bioeng 1999 63 573-682. Kristensen DB et al. Analysis of the rat dermal papilla cell proteome. Exp Dermatol 1999 8 339-340. 

Ferraris C, Cooklis M, Polakowska RR, Haake AR (1997) Induction of apoptosis through the PKC pathway in cultured dermal papilla fibroblasts. Exp Cell Res 234 37-46... 

Thornton, M. J., Hamada, K., Messenger, A. G., and Randall, V. A. (1998). Androgen-dependent beard dermal papilla cells secrete autocrine growth factor(s) in response to testosterone unlike scalp cells. J. Invest. Dermatol. Ill, 727-732. 

Rhinoceros horns are composed of densely compressed hair-like fibers over a stubby bone core that is part of the skull. They are composed of a dense growth of epidermal cells and dermal papillae, which are similar to thick hair. These are not really true hairs, since they do not grow from a follicle in the skin. Unlike the sheath-like horns of cattle and buffalo, rhino horns are mosdy solid. 

Appendageal structures commonly found within the skin are the hairs, hair follicles, associated sebaceous glands, apocrine and eccrine sweat glands, and arrector pili muscles. Hairs are formed by epidermal invaginations. These keratinized structures traverse the dermis and may extend into the hypodermis. The free part of the hair above the surface of the skin is the hair shaft, and the part deep within the dermis is the hair root, which forms an expanded knob-like structure called the hair bulb. This is composed of a matrix of epithelial cells in different stages of differentiation. Hair is composed of three concentric epithelial cell layers the outermost thin cuticle, a densely packed keratinized cortex, and a central medulla of cuboidal cells. The hair follicle consists of four major components (1) internal root sheath (internal root sheath cuticle, granular layer, pale epithelial layer) (2) external root sheath (several layers similar to the epidermis) (3) dermal papilla (connective tissue) and (4) hair matrix (comparable to the stratum basale of the epidermis). 

Objectively there is a lot of pinpoint bleeding as the loops of blood vessels in the dermal papillae are now being abraded (Figure 21.6). Abrasion must be stopped. If it were to continue, the pinpoint bleeding would increase rapidly and appear as extensive surface bleeding. 

Phenol is not considered to be carcinogenic. On the contrary, long-term histological studies show that phenol (even when the formula contains croton oil) has a protective effect against skin cancers. A logical explanation of this protective effect may lie in the fact that the cells that take the brunt of UV rays are the keratinocytes closest to the stratum corneum, the ones that form, for example, the top of the dermal papillae. On the other hand, the keratinocytes that are in the lower regions of the dermal papillae are relatively protected compared with those higher up the UV photons have been partially absorbed or diffracted by the epidermal layers above them. In addition, the sebo-cytes or keratinocytes that make up the shaft of the hair are anchored more deeply in the skin, at a depth where the harmful effects of the sun are not as severe. 

The acids destroy most of the epidermis. Histologically, the basal layer does not form the perfect sine wave that is usually shown in diagrams. On the contrary, the keratinocytes are embedded deeply and unevenly in the dermis and form the deep dermal papillae . 

Many of the deep dermal papillae actually survive the acid injury when it starts to affect the Grenz zone. 

Minoxidil. Minoxidil increases the blood flow to the follicular dermal papilla by a direct vasodilation effect on the arteriolar blood vessels (94, 95). Vasodilation is caused by the active metabolite minoxidil sulfate. 

Height (n) from basal layer to undersurface of stratum corneum Height of dermal papillae ... 

Psoriasis, a chronic inflammatory skin disease that affects approximately 1-3% of the western population [109], is characterized by hyperproliferation of keratinocytes, infiltration of inflammatory cells, and increased cytokine levels. Psoriasis is accompanied by an expansion of the superficial dermal microvasculature and elongation of capillary loops passing into dermal papillae and the papillary tip [147]. 

The epidermis is a very simple tissue composed entirely of cells. Although dermal papillae do penetrate into it from below it is readily (or potentially) detachable from these connective tissue elements. 

Hairs are keratinized structures derived from epidermal invaginations and are found almost everywhere on the body surface except for specific body sites that include the palms, soles, and mucocutaneous junctious (Figure 1.1, Figure 1.3). The distal or free part of the hair above the smface of the skin is the hair shaft. The part within the follicle is the hair root, which has a terminal, hollow knob called the hair bulb, which is attached to a dermal papilla. 

The hair follicle consists of four major components (1) internal root sheath (internal epithehal root sheath), (2) external root sheath (external epithelial root sheath), (3) dermal papilla, and (4) hair matrix. The cells covering the dermal papilla and composing most of the hair bulb are the hair matrix cells. These are comparable to stratum basale cells of regular epidermis except that they are more lipid deficient and produce harder keratin than their epidermal counterparts. 

The external epithehal root sheath is composed of several layers of ceUs similar to the epidermis, with which it is continuous in the upper portion of the folhcle. External to this layer is a homogeneous glassy membrane corresponding to the basal lamina of the epidermis. The entire epithehal root sheath (internal and extanal) is enclosed by a dermal root sheath composed of collagen and elastic hbers richly supplied by blood vessels and nerves, especially in the dermal papilla. 

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