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.