Integumentary System: Layers of Skin & Functions – Dermis
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Integumentary System: Layers of Skin & Functions – Dermis

Okay, let’s continue our discussion of the
integumentary system with the deepest layer of the skin. So remember the epidermis is going to be superficial
and right underneath it will be the dermis, which
is quite a bit more substantial, both in terms of size as well as contents. Okay, so the dermis is situated between the
more superficial epidermis and the deeper subcutaneous or hypodermal region. And it’s mentioned before there are lots of
stuff in there. So you’ll have hair roots, you’ll have muscles
associated with hair, you’ll have sensory receptors, you’ll have
glands and very importantly, particularly in terms of the survival of the
epidermis, you’re going to have a huge amount of blood
supply. So particularly in a resting adult,
you’ll have up to 10% of the body’s blood traveling through the dermis at that time. Now, remember the epidermis is completely
avascular, so for all the nutrients and supply of the epidermis, this is all coming
from the dermal layer. Now, the dermis is composed of less types
of cells. Most of the cells of the dermis are fibroblasts. And I wanna spend some time of the suffix
blast. Any time you see the term blast,
you know that that type of cell is either embryological or in utero. Or it’s going to actually synthesize or create
something. So in the case of the dermis you’re going
to have the creation of collagen or elastic fibers. And this will play a big role in terms of
the tensile strength of your skin. So if you think about being able to pinch
your skin, this is all because of the dermis. Similar to what you have in the epidermis,
you’ll have macrophages, so able to engulf microbes or things that should
not be in the dermis. And then in the deepest layers of the dermis
you’ll have adipocytes. So these are those fat cells. So the deepest portion fo the dermis,
remember is very closely associated with the hypodermis. All right, so they’re two divisions of the
dermis. You’re going to have the smaller, Papillary
region, Which is only about 20% of the dermis and
then the thicker reticular region, which is about 80% of the
dermis. And the reticular region really is gonna have
more of those components of the dermis. So those glands as well as sensory receptors. But one thing that’s particularly important
in the papillary region, specifically in the thick skin are these ridges. So you’re gonna have projections of the dermis
into the epidermis. And then, similarly,
in the epidermis you’re gonna have projections down into the dermis. So it’s creating a pattern that’s very specific
and unique to individuals. So this is what’s actually giving you fingerprints. So with the sweat gland secretions in this
region any time you press your finger down, you will
have your own unique fingerprint. So very important in terms of the field of
dermatoglyphics. Now, in the reticular region,
it’s a bit more organized in terms of how the collagen and the elastic fibers are. And they’re very distinct, and
they create what’s referred to as lines of cleavage or tension lines. And occasionally you’ll see this referred
to as langer lines, particularly in terms of the clinical field. So as you can see these fibers are in a very
distinct pattern. And this can play a big role in terms of how
wounds heal. So if you have a wound that is going to go
through this arrangement of the elastic and collagen fibers,
particularly those elastic fibers. That will cause the wound to gape, it will
not heal as well so you will have a bit more scar tissue and a
gaping wound. Whereas, if you had it
parallel to the tension lines that wound will not gape as much. You have a much better chance of healing with
only a fine scar. So think about it, what field is this particularly
important? Plastic surgery. So plastic surgeons know these tension lines
like the back of their hand, particularly in the facial region. So we’re gonna continue this discussion in
terms of the hypodermis next, so the deepest layer of your integumentary system.

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