The Dermis - Video Tutorials & Practice Problems

Introduction to the Dermis

In this video, we're going to begin our lesson on the dermis. And so recall from our previous lesson videos that the cutaneous membrane or the skin is actually made up of two layers. The first layer is the epidermis, which we already covered in our previous lesson videos. And the second layer is actually the dermis. And so the dermis can be defined as the second layer of the skin that lies deep to the epidermis. And so it is underneath of the epidermis and the dermis itself actually consists of these two different layers. And so the first layer of the dermis is the papillary layer. And the second layer of the dermis is the reticular layer. And so notice over here on the right, we have a diagram of the integumentary system and notice that in pink, we have highlighted the dermis and notice that the dermis has these two layers. The first layer is the pai layer which is more superficial and relatively thin. And then the other layer of the dermis is the reticular layer which is much thicker and makes up the vast majority of the dermis. And so moving forward in our course, we're going to talk about each of these dermal layers in their own separate videos starting with the papillary layer. And so I'll see you all in our next video.

1st Dermal Layer

So we already know from our last lesson video that the dermis of the skin consists of two dermal layers, the papillary layer and the reticular layer. And in this video, we're going to focus on the first dermal layer which is the papillary layer. And so the papillary layer is actually the more superficial layer of the dermis. And so it lies immediately underneath of the epidermis, but above the reticular layer of the dermis and the papillary layer of the dermis only makes up about 1/5 or about 20% of the total amount of dermis. And so the papillary layer is a relatively small layer in the dermis and the pap layer is actually made up of ollar connective tissue, which recall from our previous lesson videos is a type of loose connective tissue. And recall from those previous lesson videos on AOL or connective tissue that AOL connective tissue is pretty much found underneath of all epithelial tissue, including the epithelial tissue found in the epidermis. And so really, it's no surprise that aerio connective tissue is found in the pap layer which lies immediately underneath of the epithelial tissue of the epidermis. Now, the capillary layer is going to have vascular tissue. And so it does have blood vessels, specifically, it has lots of capillaries which are really small blood vessels. And so this allows for the delivery of nutrients to the epidermal cells that lie above. Also, the papillary layer contains lymphatic vessels as well, which allows for immune cells to be transported. And so immune cells can actually freely move through the loose aerial or connective tissue in order to fight pathogens that may have made it through the epidermis. And also the papillary layer has these tactile corpuscles which are also known as Mesner Corpo named after the scientist corpo are really just small structures. And the term tactile recall is associated with touch. And so these tactile or Mesner Corpo are really just nerve endings encapsulated in connective tissue that allow for touch sensations of touch. So they essentially serve as touch receptors. And so, in addition to the tactile epithelial cells found in the epidermis, uh the tactile Mesner corpuscles are touch receptors in the papillary layer of the dermis that also allow for touch sensations. Now, in the papillary layer, there are also other free nerve endings that allow for other sensations such as hot and cold temperatures as well as detections and sensations of pain and itching. For example. Now, the papy layer is named because of the presence of dermal papel. And so these dermal paille are really just folded projections that actually indent the epidermis and cause these epidermal ridges. And so together the dermal paille, these folded projections and the epidermal ridges create what are known as friction ridges. And these friction ridges are ridges that are on the surface of the epidermis, mainly in thick skin such as the palms of our hands and our fingertips as well as the soles of our feet. And as their name implies, these friction ridges allow for increased friction that enhance our grip. And they also help to produce fingerprints. And so let's take a look at our image down below where we can piece some of these things together. So notice over here on the left hand side, we're zooming in on the person's hand and uh we're focusing in on the palm of the hand and the fingertips here which we know is made up of thick skin and the thick skin has a higher tendency to have these friction ridges and the friction ridges help to create the fingerprints. As you we see here, these unique patterns of fingerprints. Now, uh notice in this diagram of the integumentary system, you can see the epidermis which lies above which we already covered in our previous lesson videos. And now we're focused on the dermis. And again, the dermis consists of both the papillary layer, which is the main focus of this video as well as the reticular layer which we'll cover in our next lesson video. And so notice that only the papillary layer of the dermis is colored here in this image. And so again, it lies immediately underneath of the epidermis. And it is named for the presence of these dermal pali. And so the dermal paille again are these folded ridges that you can see. I'm tracing here and those folded ridges ultimately indent the epidermis as well. And these are epidermal ridges and the friction ridges ultimately appear on the surface of the epidermis. And so notice here in green, we're highlighting just one of these dermal paella. Now, what you'll also notice is that in the papillary layer of the dermis are these Mesner corpo or tactile corpo, which are shown here in yellow. And again, those are going to essentially be touch receptors that allow for touch sensations. And then you can also see capillaries in the papillary layer as well, which again allows for the delivery of nutrients to the avascular epithelial tissue of the epidermis. And so, uh again, uh because the papillary layer only makes up a relatively small portion of the dermis. Uh this means that the dermis is going to be made up mostly of the reticular layer that lies immediately underneath. And so we'll get to talk more about the reticular layer of the dermis in our next lesson video. But for now, this year concludes our brief lesson on the papillary layer and we'll be able to get some practice applying these concepts and learn more about the dermis as we move forward, so I'll see you all in our next video.

The Dermis Example 1

So here we have an example problem that says if someone did not have a papillary layer in their dermis, which of the following would occur and we've got these four potential answer options down below. Now, option A says they would become more susceptible to skin cancer. However, the papillary layer of the dermis does not play a direct role in preventing skin cancer. The papillary layer does have blood vessels to help nourish the cells in the epidermis. But the papillary layer of the dermis lies underneath of the epidermis. So it does not prevent UV light from the sun from hitting those epidermal cells. And therefore, it doesn't play a direct role in preventing skin cancer and that's why we can eliminate answer option. A. Now, option B says they would no longer be able to thermo regulate via the skin. Now, recall from our previous lesson videos that thermoregulation of the skin can occur via vasoconstriction and vasodilation of blood vessels. And we know that the papillary layer does have blood vessels. So it does play a role in thermoregulation of the skin. However, thermoregulation of the skin is not unique to the papillary layer because the reticular layer of the dermis also has blood vessels that can vasoconstrict and vasodilate and contribute to thermoregulation of the skin as well. And so for that reason, option B is not going to be the best answer for this example problem. Now, option C says the epidermis would be more firmly anchored to the dermis. However, this is actually the exact opposite of what would happen. Recall that the papillary layer of the dermis has dermal papillae and those dermal papilae actually increases the surface area of contact between the dermis and the epidermis, which actually allows for more firm anchoring. And so that means that without the papillary layer, there would be less firm anchoring and this is suggesting more firm anchoring without the papillary layer. So for that reason, we can eliminate answer option C and of course, this leaves answer option D as the only option and it is the correct answer which says they will lose some sensation of touch. Now, recall that the papillary layer of the dermis has nerve endings specifically in structures known as the tactile or Meisner corpuscles. And so those are going to allow for sensations of touch and without the papillary layer and without those tactile and Meisner corpuscles, there would be less sensations of touch. And so for that reason, we can indicate that option D is the correct answer to this example problem and that concludes this example. So I'll see you all in our next video.

2nd Dermal Layer

In this video, we're going to talk about the second dermal layer which is the reticular layer. And so the reticular layer of the dermis actually lies deep to the papillary layer of the dermis. Meaning that the reticular layer lies underneath of the pap layer. And the reticular layer actually makes up about 4/5 or about 80% of the total amount of dermis. And so the reticular layer makes up the vast majority of the dermis. And this actually makes the reticular layer, the largest layer of the cutaneous membrane or the largest layer of the skin. And so, because the reticular layer is the largest layer of the skin, it's largely going to define the properties of the skin. And so the reticular layer of the dermis is actually made up of dense irregular connective tissue. And so, recall from our previous lesson videos that dense irregular connective tissue is characterized by having these really densely packed and irregular or random arrangement of mostly collagen protein fibers, but also elastic protein fibers as well in the extracellular matrix. And recall that the irregular or random arrangement of fibers allows dense irregular connective tissue to resist forces in multiple directions and also to display elasticity in multiple directions. And so, because the reticular layer again, makes up the vast majority of the skin, the dense irregular connective tissue is also going to give those properties to the skin. And so the skin is able to resist forces in multiple directions and it is quite stretchy and can have elasticity in multiple directions as well. Now, the reticular layer also can have a variety of accessory structures within it including some sweat glands and oil glands. It can also have hair roots and it can also have these pressure receptors that are called lamellar corpuscles and these lamellar corpo are also sometimes referred to as Pasian Corpo. The pinion is named after the specific scientist that discovered them and the term lamellar actually refers to the onion like layers or the cinnamon cinnamon bun like layers that these uh lamellar or pinion corpus make. And again, these lame or pasin corpo lie in the reticular layer of the dermis and they serve as pressure receptors to allow for pressure sensations. Now, recall from our previous lesson videos, the term reticular means netlike and the term reticular in the reticular layer of the dermis does not actually indicate the presence of reticular protein fibers in the cell matrix. Instead, the term reticular in the reticular layer refers to the netlike arrangement of again, mostly collagen protein fibers but also some elastic protein fibers as well. And recall that the collagen protein fibers allow for strength and the elastic protein fibers allow for elasticity or the ability to stretch significantly, but then return back to its original shape after stretching. And so again, because of the net like arrangement or irregular random arrangement of many of these collagen and elastic protein fibers, it allows the skin to have shrink and resisting forces in multiple directions and also to have elasticity in multiple directions. Now, although uh many of the fibers do have this netlike arrangement, it is important that there are also many fibers in the reticular layer of the dermis that may actually orient in one direction in a parallel fashion to the surface of the skin. And so this actually creates what are known as cleavage lines. And cleavage lines are also sometimes referred to as tension lines. And so these cleavage lines or tension lines are the result of parallel orientations of many collagen fibers in the particular layer of the dermis. And those parallel orientations of many of the collagen fibers ultimately create these surgically relevant invisible lines and those sur surgically relevant invisible lines are the cleavage lines or the tension lines. Now, these lines are not, again, they are invisible lines. So they are not visible on the surface of our skin. However, they can be indirectly detected based on the way that our skin resists tension as well as the way that our skin behaves when it is cut. And so again, these cleavage lines or tension lines are relevant to surgeons. And the reason that they are so relevant to surgeons is because when the skin is actually cut parallel to these cleavage or tension lines, it actually allows for faster healing. And so the tissue will actually heal faster when the skin is cut parallel to cleavage or tension lines. So surgeons need to be very, very familiar with these cleavage or tension lines. Although they are invisible on the skin, again, they can be detected through the way that our skin resists tension forces. And so let's take a look at our image down below where we can piece some of these ideas together. And so notice over here on the left hand side, we have the diagram of the integumentary system. And notice that only the reticular layer of the dermis is being colored here. And notice that the particular layer of the dermis makes up the vast majority of the dermis. And it is the largest layer of the cutaneous membrane or the largest layer of the skin. And so largely defines the properties of the skin. It is mostly made up of dense irregular connective tissue, which you can see right here those collagen and elastic protein fibers in this netlike arrangement. And so here we can label the collagen and elastic protein fibers. And again, uh notice that there are plenty of accessory structures within the particular layer of the dermis, including hair roots and sweat glands and also sebaceous or oil glands as well. And you'll also notice that there are lots of blood vessels as well. There are blood vessels. Uh so it is vascular and you can also see these yellow structures that you see here. Those are the lame, the lame or the pinion corpuscles, which are the pressure receptors that allow for sensations of pressure. And again, uh it's difficult to see here, but they do have this onion like arrangement or the cinnamon bun like arrangement. And that is really why they're called la Meller corpus. Now, uh again, many of these collagen and elastic protein fibers can actually uh form parallel orientations that create these cleavage lines. And again, the cleavage lines are invisible lines. Uh And in this diagram, we're only showing you the line so that you can actually uh see them and get an idea of what they look like. But ultimately, these lines that you can see all throughout the body are the result of again, parallel orientations of many collagen fibers in the particular layer. And again, surgeons need to be very, very familiar with these cleavage lines because again, when the skin is cut parallel to them, it actually allows for faster healing. Now, over over here, what we have is a leather jacket. And so what's important to note is that leather is actually made from the dermis of animal skins. And again, the reticular layer makes up the vast majority of the dermis and is made up of dense irregular connective tissue. And so a dense irregular connective tissue is able to resist forces in multiple directions and have elasticity in multiple directions as well. And really, we find those properties in leather materials as well. And so this here concludes our brief lesson on the second dermal layer, the reticular layer of the dermis, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

The Dermis Example 2

So here we have an example problem that asks which of the following may occur in someone who does not have dermal paille. And we've got these four potential answer options down below. Now recall that dermal paille are these folded projections found in the Papiri layer or the most superficial layer of the. And they actually create folds in the epidermis as well called epidermal ridges. And together these dermal paille and epidermal rigid form friction ridges on the surface that are directly associated with our fingerprints. And so without the dermal paille, we would not be able to have fingerprints. And so notice answer option A says they would no longer have a fingerprint and that is the correct answer to this example problem. So we can indicate that A here is correct. Now, notice that option B says their skin would take longer to heal after getting cut. Now, dermal paille do have blood vessels and so those blood vessels can help nourish the epidermal cells. However, the dermal paille are not directly linked to the rate of healing. There are many different factors that come into the healing process. And so uh option B is not the best answer option. Now, option C says their skin would be, their skin wouldn't be able to thermo regulate. Now again, dermopathy do have blood vessels that can undergo vasoconstriction and vasodilation for thermoregulation. However, thermoregulation of the skin is not unique to the dermo papillate because the particular layer of the dermis that lies underneath also has blood vessels that can undergo vasoconstriction and vasodilation and help to thermo regulate the skin. So for that reason, option C is not the best answer. And then option D says they would be more likely to get skin cancer. But again, the dermo paille are not directly involved with preventing skin cancer. They do not prevent UV light from the sun from hitting those epidermal cells. And so they don't protect those cells from cancer and they don't prevent cancer. And so for that reason, we can eliminate option D. So again, a here is the correct answer to this example and I'll see you all in our next video.

Which part of the integument is responsible for providing strength and flexibility?

• A. Papillary layer.
• B. Dermal papillae.
• C. Epidermis.
• D. Reticular layer.