Abstract
The human skin is a complex organ that provides a protective barrier against fluid loss from within, and against assault from the external environment by chemicals (irritants), physical agents (mechanical forces, UV radiation), and biological pathogens (Proksch et al., 2008). Moreover, skin contributes to thermal regulation by sweating. The skin consists of three layers: the hypodermis, loose connective tissue that contains the subcutaneous fat; the dermis, a connective tissue (rich in collagens and glycosaminoglycans synthesized by dermal fibroblasts) containing blood supply and nerves, which supports the epidermis and the epidermal appendages (hair follicles sebaceous glands, and sweat glands); and the epidermis, the outer, stratified squamous epithelium of keratinocytes from which the appendages are derived and which forms the skin barrier (Figure 12.1). Other resident cells of the epidermis are melanocytes, responsible for skin pigmentation, Langerhans cells (antigen-presenting dendritic cells), Merkel cells and other sensory receptors and nerve endings. In normal epidermis, a steady state exists between production of new cells from keratinocytes resident in the basal layer and the loss of terminally differentiated cells from the skin surface (Blanpain and Fuchs, 2009). Histologically, four layers of keratinocyte differentiation can be recognized within the epidermis: the basal, spinous, granular, and stratum corneum layers. Each represents a stage in progression through the cell terminal differentiation program (Figure 12.1). Epidermal physical barrier function against water loss and penetration by chemical, physical, and biological agents resides mainly within the stratum corneum, although recent work suggests that a network of tight junctions within the granular layer may also be important in some circumstances (Kirschner et al., 2009). The specific immunological barrier function of the epidermis is largely associated with the Langerhans cells (Romani et al., 2006, 2010), although keratinocytes also seem to play a role, particularly in the innate immune response (Lai et al., 2010; Lai and Gallo, 2008).
Original language | English |
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Title of host publication | Connexin Cell Communication Channels: Roles in the Immune System and Immunopathology |
Subtitle of host publication | Roles in the Immune System and Immunopathology |
Editors | E. Ovideo-Orta , B.R. Kwak, W.H. Evans |
Publisher | CRC Press |
Pages | 233-253 |
Number of pages | 21 |
ISBN (Electronic) | 9781439862582 |
ISBN (Print) | 9781439862575 |
DOIs | |
Publication status | Published - 2013 |
Keywords
- connexins
- epidermis
- inflammatory disorders
- immune system
ASJC Scopus subject areas
- General Biochemistry,Genetics and Molecular Biology
- General Medicine
- General Immunology and Microbiology