Go Back to the Top To Order, Visit the Purchasing Page for Details 1 Chapter 1 Structure and Function of the Skin The skin is the human body’s its largest organ, covering 1.6 m2 of surface area and accounting for approximate- ly 16% of an adult’s body weight. In direct contact with the outside environment, the skin helps to maintain four essential bodily functions: ① retention of moisture and prevention of permeation or loss of other molecules, ② regulation of body temperature, ③ protection of the body from microbes and harmful external influences, and ④ sensation. To understand cutaneous biology and skin diseases, it is very important to learn the structure and functions of normal human skin. A. Skin surface The skin surface is not smooth, but is laced with multiple net- works of fine grooves called sulci cutis. These can be deep or shallow. The slightly elevated areas that are surrounded by shal- lower areas of sulci cutis are called cristae cutis. Sweat pores fed crista cutis by the sweat glands open to the cristae cutis (Fig. 1.1). The orientation of the sulci cutis, which differs depending on body location, is called the dermal ridge pattern. Fingerprints and sulcus cutis patterns on the palms and soles, which are unique to each person, are formed by the sulci cutis. Elastic fibers also run in specific directions in deeper parts of the skin, with the direction depend- aabcdefg h i j klmnopqr ing on the site. Some skin diseases, such as epidermal nevus, are known to occur along specific lines distributed over the body, the Blaschko lines (Fig. 1.2). These lines are thought to be associated a bbcdefg h i j klmnopqr abccdefg h i j klmnopqr Fig. 1.1 Appearance of the skin surface. a: Cristae cutis (triangle) and sulci cutis (arrows). b: Nevus-cell nevus along the cristae cutis. c: Fig. 1.2 The Blaschko lines. Sweat pores fed by sweat glands open to the Many dermatological disorders appear along these lines, such as epider- cristae cutis (arrows). mal nevus and linear scleroderma (Bolognia JL, et al. J Am Acad Derma- tol 1994; 31:175-90). 1 1 2 1 Structure and Function of the Skin hairir arrectorrrector pilipili muusscclele sweweat porepore apocrinepocrine sweweat glglandnd epidermie epidermi p i d dermdermal papillpilla hornyhorny ccellell layyerer e r m i s s epidermepidermal reterete ridgeridge s papillpillaryry ddermiermis subsubpapillpillarryy ddermiermis epidermepidermal bbasaseementment memmembranene infinfundindibubulum eccrineeccrine sweweat glglandnd dermid dermi e r sebabaceoceousus glglandnd m i s s reticreticular dermidermis s hairir bubulgelge hairir folliclefollicle dermdermal hairir papillpilla hairir bubulb hairir matrixtrix sub s u b c ssububcutanneoeouuss u t fat a neo n e o us u s ti t i ssu s s u e e m fasascicia m u us us s cle cle c l e Fig. 1.3 Structure of the skin. (Nakagawa H, editor. Dermatological disorders. In: Symphonia Medica Nursing (Vol.19). Nakayama-Shoten; 2001. p.3). with the direction in which the differentiated cell clones extend during fetal skin development. Skin generally consists of a three-layer structure: the epider- mis, dermis and subcutaneous tissues (Fig. 1.3). At the boundary between the epidermis and dermis are finger-like projecting structures (the dermal papillae) that project into the overlying tis- sue (the epidermis) (Fig. 1.30). The portion of the epidermis that projects into the dermis is called the epidermal rete ridge, and the portion of the dermis that projects into the epidermis is called the dermal papilla. Go Back to the Top To Order, Visit the Purchasing Page for Details.