Skin: Architecture and Function
The skin is the largest organ of the human body. It covers approximately 1–2 m2 of surface area and accounts for around 12–16 % of an adult’s body weight. In direct contact with the outside environment, the skin provides the following essential functions:
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Skin: Architecture and Function Gerd G. Gauglitz and Jürgen Schauber
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Introduction
The skin is the largest organ of the human body. It covers approximately 1–2 m2 of surface area and accounts for around 12–16 % of an adult’s body weight. In direct contact with the outside environment, the skin provides the following essential functions: • Retention of moisture and prevention of loss of other molecules • Barrier function against harmful external influences • Immune function and protection of the body from microbes • Sensory function (e.g. heat, cold, touch, pressure, vibration, tissue injury) • Endocrine function (e.g. vitamin D production) • Regulation of body temperature To understand cutaneous biology, wound healing and skin diseases, it is critical to be aware of the defined structures and functions of normal human skin. Human skin consists of a stratified, cellular epidermis and an underlying dermis of connective tissue which together form the cutis (Fig. 1.1). The dermal–epidermal junction is undulating and ridges of the epidermis, known as rete ridges, project into the dermis. The junction provides mechanical support for the epidermis and acts as a partial barrier against larger molecules.
G.G. Gauglitz, MD, MMS (*) Department of Dermatology and Allergy, Ludwig Maximilian University, Munich, Germany Scar Clinic, Department of Aesthetics, Department of Infectious and Sexual Transmitted Diseases, Department of Dermatology and Allergy, Ludwig Maximilian University, Frauenlobstr. 9-11, Munich 80337, Germany e-mail: [email protected] J. Schauber, MD Department of Dermatology and Allergy, Ludwig Maximilian University, Munich, Germany L.-P. Kamolz, D.B. Lumenta (eds.), Dermal Replacements in General, Burn, and Plastic Surgery, DOI 10.1007/978-3-7091-1586-2_1, © Springer-Verlag Wien 2013
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G.G. Gauglitz and J. Schauber
Hair
Arrector pili muscle Sweat pore Apocrine sweat gland
Epidermal basement membrance Eccrine sweat gland
Horny cell layer Papillary dermis Subpapillary dermis
Infundibulum
Reticular dermis
Dermis
Sebaceous gland
Epidermis
Dermal papilla Epidermal rete ridge
Hair bulge
Hair follicle Dermal hair papilla Hair bulb Subcutaneous tissue
Hair matrix Subcutaneous fat
Muscle
Fascia
Fig. 1.1 Structure of the skin (From Nakagawa 2001)
Below the dermis, a fatty layer, the panniculus adiposus, exists, usually designated as ‘subcutaneous fat’. It is separated from the rest of the body by a vestigial layer of striated muscle, the panniculus carnosus (Fig. 1.1). Two variants of human skin can be differentiated: Glabrous skin (non-hairy skin), found on the palms and soles, is grooved and its surface shows individually unique configurations by continuously alternating ridges and sulci, known as dermatoglyphics. It is characterised by a thick epidermis divided into several well-marked layers including a compact stratum corneum, by the presence of encapsulated sense organs within the dermis and by a lack of hair follicles and sebaceous glands. Hair-bearing skin, on the other
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