Biomedical Engineering Reference
In-Depth Information
Basement
membrane
Dermal
papilla
Epidermis:
0.1 mm approx.
Elastin
fiber
Collagen
fiber
Dermis:
1-2 mm
Interfibrillar
matrix
3.1
Structure of skin.
the forces or displacements are meaningful but not large enough to cause structural
damage.
The skin serves many functions. It serves as a mechanical barrier keeping
outside environmental agents (bacteria, toxins, chemicals, UV radiation) sepa-
rated from the internal parts of the body. It also serves as a protective covering that
shields our bodies from minor trauma and abrasions
1
as we perform the day to day
activities of moving and handling objects. The skin also helps preserve the
temperature of our bodies by preventing heat loss in cooler environments and by
alternately mediating heat loss through sweating and increased blood flow.
3.2 Structure of skin
The skin is made up of two layers, epidermis and dermis (Fig. 3.1). The epidermis
is 80 µm (or about 0.1 mm) thick, is multicellular and has four sublayers: the
stratum basalis, the stratum spinosum, the stratum granulosum and the stratum
corneum.
1
New cells are continuously made in the deepest layer of the epidermis,
the stratum basalis and move outward toward the surface of the skin.
2
Since the
epidermis is not supplied with blood vessels (and therefore only obtains its
nutrients from the dermis), cells near the surface die and form the outermost layer
of the epithelium or the stratum corneum.
Epidermal cells are strongly attached to one another by tight junctions and
desmosomes (desmosomes also help connect these cells to their neighbors below).
The lowermost layer of epithelial cells right above the basement membrane is
attached to the membrane by hemi-desmosomes. Such junctions provide the
