Skin structure PDF/ PPT

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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: retention of moisture and prevention of permeation or loss of other molecules,
regulation of body temperature, protection of the body from microbes and harmful external influences, and
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-
crista cutis
lower areas of sulci cutis are called cristae cutis. Sweat pores fed
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- a b c d e f g h
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 b c d e f g h i


a b c d e f g h i j
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).

2 1 Structure and Function of the Skin



arrector pili muscle
sweat pore
apocrine sweat gland


dermal papilla horny cell layer
epidermal rete ridge
papillary dermis
subpapillary dermis
epidermal basement membrane infundibulum
eccrine sweat gland


sebaceous gland reticular dermis
hair bulge

hair follicle
dermal hair papilla
hair bulb
hair matrix


subcutaneous tissue




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.


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