the epidermis is made up of four
different types of cells
the first type of cell is an epithelial
cell known as keratinocytes
this creates a keratin layer which is
very strong intermediate filament found
inside of these cells a second type of
cell found in the epidermis is
melanocytes
melanocytes produces melanin which is
the substance that allows us to block
uv rays from the sun
a third type of cell found in our
epidermis are the longer han cells
or the immune cells which are actually
macrophages that help us
to block bacteria that are trying to get
inside of the body
and finally we have the tactile
epithelial cells
also referred to as merkel cells these
are going to help us
with feeling or cutaneous sensations
there are two different types of skin
found in the
integument the first type of skin is
thin skin this is what covers the
majority of our body
and excludes the skin of our palms
as well as the palmar surface of our
digits
and our toes the second type of skin
which is going to cover the palms the
digital surfaces of our digits
and the palms of our feet is going to be
the thick skin
this skin is hairless
the epidermis is composed of multiple
layers
the thin skin contains four layers
whereas the thick skin
contains five layers starting from the
deepest layer of the epidermis
we have the stratum basale the stratum
basale is made up of stem cells and
in this layer we are going to be as
close to the dermis as possible
the reason why is because epithelial
tissue
is avascular meaning they do not have a
source of nourishment
but the stratum basale is close to the
dermis therefore it is
nourished by the blood vessels in the
dermis
also in this layer is where we will find
our melanocytes
just above are superficial to the
stratum basale
is the stratum spinosum the stratum
spinosum
is eight to ten layers of epithelial
cells
keratinocytes specifically that are lie
alive and well also being nourished from
the dermal layer
just superficial to the stratum spinosum
is the stratum granulosum
this is a layer of about three to five
keratinocytes
the difference in this layer however is
now we are starting to transition
from living cells in the epidermis to
non-living cells
the reason why is we are starting to be
too
far away from the nourishment of the
dermis
and so these cells do not have access to
nutrients and so they are starting to
die
now located in thick skin only we have a
layer
called the stratum lucidum it is
actually called the stratum lucidum
because this layer appears
clear when you look at these cells under
the microscope
now the keratinocytes are starting to be
flattened they are not they do not look
as squamous as they used to and they're
starting to look a little bit more flat
there's about four to six layers of this
strata
and then finally we have the stratum
corneum
the stratum corneum is made up of up to
50 layers of keratinocytes
that are dead and pretty much flattened
they have very little cytosol inside of
these cells
it is this layer that is constantly
sloughing off
as you go throughout life as the skin
grows
it grows from that stratum basale layer
where you have the stem cells up toward
the stratum corneum
so it's okay that these cells are
breaking off or sloughing off
because they are being replaced by the
layers below
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