Biomedical Engineering Reference
In-Depth Information
6
Understanding the cellular basis of skin growth
L. GUO
Brigham and Women's Hospital, USA
Abstract:
Skin is a complex body organ with several tissue layers and many
more cell types. A good knowledge on the exact composition, structure and
development of the skin is important in understanding its function and
eventually in engineering artificial skin.
Key words:
dermis, epidermis, hair follicles, keratinocytes, skin.
6.1
Introduction
Skin is the body's largest organ and makes up approximately 16% of a human's
total body weight. It performs several necessary and important functions and its
loss presents a serious medical challenge. Often, physicians can replace lost skin
by grafting in undamaged skin from another area of the body. However, sometimes
artificial skin constructs can be utilized for large skin defects or to minimize donor
site morbidity. To create better skin substitutes, it is important to learn more about
the structure and functions of skin. This chapter aims to describe skin's function
and structure as well as the different cell types that make up the skin.
Mammalian skin has evolved to fulfill a number of complex and diverse
functions. It protects against outside materials and some types of radiation,
regulates heat loss and mediates sensation. The skin is relatively impermeable,
which prevents internal fluids from escaping. The skin is also the site for synthesis
of vitamin D (an important regulator of calcium and phosphate metabolism), as
well as a site for biochemical interconversions (e.g. androgenic steroids) and
excretion of ingested toxins. Lastly, the skin's aesthetic attributes affect social
interaction.
6.2 Structure of the skin
The skin consists of a stratified, cellular epidermis and an underlying dermis of
connective tissue (
Fig. 6.1)
. Below the dermis is a fatty layer, usually designated
as 'subcutaneous'. In most mammals (e.g. mice) this fatty layer is separated from
the rest of the body by a flat sheet of striated muscle (Rook
et al.
, 1986). Dermal
flexibility and elasticity united with epidermal strength and impermeability allows
for the skin to serve as a protective barrier.
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