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- providing oxygen and nutrients, via blood in the tiny vessels that run in
the ground substance, to the living part of the epidermis
- removing waste products of metabolism from the epidermis, which are also
carried away in the blood
- providing shape and form to the body, by holding all its structures together
- contributing to skin color, particularly in people with little melanin
in the epidermis.
Organs in the dermis have special functions of their own:
- regulation of body temperature through control of blood flow and
sweating
- skin sensations of touch, pain, heat and cold.
Sweating
One of the important functions of skin is in helping to control body
temperature.
All primates (a group that includes apes and humans)
have glands in the skin from which they produce sweat (see page 34)
and control body temperature by evaporation (horses have them too). This
sweat, which we don't notice, is called insensible perspiration.
Evaporation needs heat energy, so evaporating sweat removes heat from
the body and keeps down the body temperature (a process called thermoregulation).
Sweat production is a response sometimes to external temperature changes,
sometimes to internal stimuli - such as a highly seasoned curry! - and
occasionally to
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Body temperature
regulation by blood flow control: (left) blood vessels in the dermis get
narrower when cold, so limiting the amount of heat brought by the blood
to the skin surface and lost; (right) the vessels widen when warm, so
that heat is brought to the surface and escapes.
stress, as a reaction to increased production of adrenalin.
Control of body temperature through sweat production
is essential for life. Unfortunately this mechanism encourages effects
which are now considered unacceptable, such as excessive wetness and unpleasant
markings on clothing, and body odour (malodour).
Most of the sweat produced by the body comes from
the eccrine glands. Up to two litres can be lost in an hour! While its
primary function is temperature control, eccrine sweat also provides a
useful method of removing acids and some waste products (toxins) from
the body.
Men sweat more than women do; on the other hand,
women have a higher perspiration pH (pH 7) compared with men (pH 5.61).
Different skin types and their characteristics
As skin grows older, we start to see differences in its appearance -
and not only differences in our own skins but differences between people
of the same age. The changes are determined fundamentally by our inherited
skin type, its response to its environment and sometimes our overall health.
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