Chapter 1

Skin structure and function
Introduction
The integument or skin is the largest organ of the body, making up 16% of body weight, with a surface area of 1.8 m2. It has several functions, the most important being to form a physical barrier to the environment, allowing and limiting the inward and outward passage of water, electrolytes and various substances while providing protection against micro-organisms, ultraviolet radiation, toxic agents and mechanical insults. There are three structural layers to the skin: the epidermis, the dermis and subcutis. Hair, nails, sebaceous, sweat and apocrine glands are regarded as derivatives of skin (see Figure 1.1). Skin is a dynamic organ in a constant state of change, as cells of the outer layers are continuously shed and replaced by inner cells moving up to the surface. Although structurally

Figure 1.1 Cross-section of the skin.

2 Aromadermatology
Table 1.1 Layers of the skin.
Skin layer

Description

Epidermis

The external layer mainly composed of layers of keratinocytes but also containing melanocytes,
Langerhans cells and Merkel cells.

Basement membrane

The multilayered structure forming the dermoepidermal junction. Dermis

The area of supportive connective tissue between the epidermis and the underlying subcutis: contains sweat glands, hair roots, nervous cells and ®bres, blood and lymph vessels.

Subcutis

The layer of loose connective tissue and fat beneath the dermis. consistent throughout the body, skin varies in thickness according to anatomical site and age of the individual.

Skin anatomy
The epidermis is the outer layer, serving as the physical and chemical barrier between the interior body and exterior environment; the dermis is the deeper layer providing the structural support of the skin, below which is a loose connective tissue layer, the