Salon Fundamentals
TM
Esthetics
s k i n p h y s i o l o g y
266
Maintaining elastin is important since the body
does not readily replace it.
Mast cells are also located in the dermis. These
cells respond to allergies by releasing small
granules called histamines. For example, a
wasp or a bee sting causes the mast cells to
release histamines. Taking an antihistamine
like Benadryl
®
decreases the effect of the
histamine that is released. Keeping ice on the
area that was stung decreases the blood flow to
the area. This decrease in blood flow keeps the
"local reaction" from spreading.
The dermis has two layers: the papillary dermis
and the reticular dermis, which contain a variety
of glands. These layers nourish the epidermis
and connect the dermis to the layer below it, the
subcutaneous layer.
Papillary Dermis
The papillary dermis layer lies directly beneath
the epidermis. It is rich in blood vessels and
capillaries, which provide nutrients to the
upper layer. From the papillary layer, finger-like
projections of the
dermis extend into
the epidermis and
nourish the skin.
The papillary dermis
houses sensory nerve
endings called receptors.
Pain receptors are free
nerve endings not
associated with cells.
The Merkel cells, found in the stratum
germinativum of the palms and soles, have
specialized nerve endings associated with them.
The pain receptors detect extreme temperatures,
mechanical surface injury and chemical
applications, such as high-level chemical peels
(aggressive removal of dead skin cells).
The thermoreceptors are also free nerve
endings located in the dermis. Cold
receptors outnumber the heat receptors
by three or four times. These
thermoreceptors respond when the
temperature is changing and adapt
quickly when the temperature stabilizes.
Mechanoreceptors sense stretching, compression
or twisting of the skin. These actions distort cell
membranes which causes the mechanoreceptors
to respond. Tactile receptors are those that sense
gentle touch, pressure or vibration.
Within the dermal layer of the skin, there are four
main receptors for sensation:
·
Meissner's Corpuscles: Light pressure and
cold receptors
·
Ruffini's Corpuscles: Long-term pressure
and heat receptors
·
Pacinian Corpuscles: Deep pressure and
pain receptors
·
Krause's End Bulbs: Pressure and pain
receptors
Have you ever seen a thin foam
mattress with projections
on one side that look like
egg crates? This egg crate
mattress helps soften your
bed by providing pockets of
air between you and the
mattress, which is similar to
the way the papillary layer of
the dermis softens the skin.
In the summer when you walk from the heat
of the day into the cool air conditioning,
the temperature change seems extreme
at first. However, you quickly become
comfortable as adaptation occurs: that's
your thermoreceptors in action!
During pregnancy the abdominal skin stretches.
If there is a marked loss of elastin, then the
dermis is unable to return to its original size.
This damage to the elastin fibers results in skin
that wrinkles and creases, forming stretch marks.
