So let's continue our discussion now getting into the nitty-gritty or the details of the
integumentary system so we're gonna start with the most superficial layer your epidermis and
then we'll move into the deeper layers so with any discussion we need to start at the cellular level
so the smallest level and there's four main cells that we're going to discuss but first
I want to talk about what is actually composed of what are these four cells actually going to
cause the epidermis to look like so when you're talking about the epidermis a lot of times you'll
have it hear it referred to as keratinized stratified squamous epithelial tissue and
that sounds horrendous that's super long let's break it down and try to understand what these
actually mean so when we're talking about keratinized this is talking about the protein
keratin so as I just said in previous modules keratin is prolific throughout the epidermis
it is going to be very important in terms of protection against abrasions heat microbes
only allowing certain things into the into the deeper layers of the body stratified and anytime
you see stratified when you're talking Anatomy or histology just means more than one layer so
depending on whether you're talking about thick or thin skin it could be four layers
or five layers squamous squamous means flat kind of elongated cell type so particularly
when you're in the more superficial layers of the epidermis the ones that are more closely
associated with the external environment these cells are going to be extremely flat and it's
actually because these cells are dead so that's why you can slough off skin and then epithelial
is one of the main types of tissues of the body so there's four main types of body tissues we'll
talk in a lot of detail about different types of connective tissue but epithelial tissue lines
surfaces so you'll have it associated with the gastrointestinal tract but the integumentary
system or your epidermis is lining the entirety of your body so this is a type of epithelial tissue
all right so we're gonna be spending quite a bit of time on this this visual and it's a
really nice visual it it explains the four main types or it visualizes the four main types of
cells what I want to focus on right now are your keratinocytes so we're going to spend a bit more
time on this now the keratinocytes are the cell of the epidermis it composes of more than
90% of the epidermis this is what's producing that keratin protein that we've been discussing
as well as the lamellar granules so the portions that are going in between the keratinocytes
serving as an additional protection melanocytes are what's actually producing
the melanin pigment and we'll talk about this in more detail but very important in terms protection
from UVB radiation now one thing I want you to note are these almost spider like extensions of
the melanocytes these are going to be processes that are going kind of in between those keratinocytes
cells allowing for these small melanin pigments to move into the keratinocytes cells
to protect its nucleus and that's really the key role protecting the nuclei of the keratinocytes
which make up the majority of the epidermis all right Langerhans cells Langerhans cells are huge
cells you'll have these type of cells in other areas of the body so not just the epidermis and
these are a type of macrophage cell meaning that it will engulf or ingest microbes from
within the epidermis so very important in terms of immune responses if something moves into the
epidermis that shouldn't be there it will engulf that microbe and cause it to be some type of waste
that can be secreted later and lastly we have the Merkel or tactile epithelial cells these are a
type of touch receptor so important in terms of touch a very fine touch so texture or shape and
it's unique in terms of sensory receptors most sensory receptors are located in the dermis or
the layer just deep to the epidermis but the Merkel cells are going to be located actually
in the deepest layer of the epidermis so unique and we'll discuss in a bit more detail but really
important in terms of particularly in your hands really understanding what you're touching all
right so to review you're going to have keratinocytes throughout all layers of the epidermis you
can see here these are going to be a little bit larger in the deeper layers and then they get
flatter as you get more superficial so these are really where those squamous description comes in
so keratinocytes are throughout the entirety of the epidermis the other three types are mostly
located in these deeper layers so you have your melanocytes with those extensions in between
the cells you'll have the Merkel cells in the deepest layer and then you'll have Langerhans
cells so those macrophage cells typically in either the deepest layer or the second deepest
layer of the epidermis so those are the four main cells remember those as we continue our discussion
in the next module with the different different layers or the different divisions of the epidermis