The Dermis - Online Tutor, Practice Problems & Exam Prep

The dermis, the second layer of skin beneath the epidermis, consists of two layers: the papillary layer and the reticular layer. The papillary layer, made of areolar connective tissue, contains capillaries and Meissner corpuscles for touch sensation, contributing to friction ridges that enhance grip. The reticular layer, composed of dense irregular connective tissue, provides strength and elasticity, housing sweat glands, hair roots, and pressure receptors like Pacinian corpuscles. Understanding these layers is crucial for grasping skin properties and functions, including healing processes related to cleavage lines.

Introduction to the Dermis

In this video, we're going to begin our lesson on the dermis. 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. The dermis can be defined as the second layer of the skin that lies deep to the epidermis. It is underneath the epidermis. The dermis itself actually consists of these two different layers. The first layer of the dermis is the papillary layer, and the second layer of the dermis is the reticular layer. Notice over here on the right, we have a diagram of the integumentary system. Notice that in pink, we have highlighted the dermis. Notice that the dermis has these two layers. The first layer is the papillary layer, which is more superficial and relatively thin. The other layer of the dermis is the reticular layer, which is much thicker and makes up the vast majority of the dermis. 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. 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 2 dermal layers, the papillary layer and the reticular layer. In this video, we're going to focus on the first dermal layer, which is the papillary layer. The papillary layer is actually the more superficial layer of the dermis and lies immediately underneath the epidermis but above the reticular layer of the dermis. The papillary layer of the dermis only makes up about one fifth, or about 20%, of the total amount of dermis. It is a relatively small layer in the dermis and is made up of areolar connective tissue, a type of loose connective tissue that is found underneath all epithelial tissue, including the epithelial tissue found in the epidermis.

There is no surprise that areolar connective tissue is found in the papillary layer, which lies immediately underneath the epithelial tissue of the epidermis. The papillary layer has vascular tissue; it has many capillaries, which are really small blood vessels, allowing for the delivery of nutrients to the epidermal cells that lie above. Additionally, the papillary layer contains lymphatic vessels, which allow for immune cells to be transported. Immune cells can freely move through the loose areolar connective tissue to fight pathogens that may have penetrated the epidermis. Moreover, the papillary layer has tactile corpuscles, also known as Meissner corpuscles, named after the scientist. Corpuscles are small structures associated with touch, serving as touch receptors. In addition to the tactile epithelial cells found in the epidermis, the tactile Meissner corpuscles are touch receptors in the papillary layer of the dermis that also allow for touch sensations.

Also present in the papillary layer are other free nerve endings that allow for sensations such as hot and cold temperatures, as well as detections and sensations of pain and itching. The papillary layer is named because of the presence of dermal papillae, which are folded projections that indent the epidermis and cause epidermal ridges. Together, the dermal papillae and the epidermal ridges create what are known as friction ridges. These friction ridges, found on the surface of the epidermis mainly in thick skin such as the palms of our hands, our fingertips, and the soles of our feet, increase friction to enhance our grip and also help to produce fingerprints.

Let's take a look at our image below where we piece some of these elements together. Notice on the left-hand side, we're zooming in on a person's hand, focusing on the palm and the fingertips, which are made up of thick skin. The thick skin has a higher tendency to have these friction ridges, which help to create unique patterns of fingerprints. In this diagram of the integumentary system, you can see the epidermis above, and we are now focused on the dermis, consisting of both the papillary layer and the reticular layer. Notice that only the papillary layer is colored in the image, indicating its location immediately underneath the epidermis and its relation to the dermal papillae. These folded ridges indent the epidermis, creating epidermal ridges and the friction ridges on the surface of the epidermis. Highlighted in green is one of the dermal papillae, and in yellow are the Meissner corpuscles, which function as touch receptors. Also present are the capillaries in the papillary layer, enabling nutrient delivery to the avascular epithelial tissue of the epidermis.

Given that the papillary layer constitutes a small portion of the dermis, it implies that the dermis is primarily made up of the reticular layer, located immediately underneath. We'll discuss the reticular layer of the dermis in our next lesson video. This concludes our brief lesson on the papillary layer, and we will have some practice applying these concepts and learn more about the dermis as we move forward. 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 4 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 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 thermoregulate 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 papillae actually increase 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 would 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 Meissner corpuscles. And so, those are going to allow for sensations of touch. And without the papillary layer and without those tactile and Meissner corpuscles, there would be fewer 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 2nd 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 the papillary layer. And the reticular layer actually makes up about 4 fifths 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 corpuscles are also sometimes referred to as Pacinian corpuscles. The Pacinian is named after the specific scientist that discovered them. And the term lamellar actually refers to the onion like layers or the cinnamon bun-like layers that these, lamellar or Pacinian corpuscles make. And again, these lamellar or Pacinian corpuscles lie in the reticular layer of the dermis and serve as pressure receptors to allow for pressure sensations. Now recall from our previous lesson videos, the term reticular means net-like. And the term reticular in the reticular layer of the dermis does not actually indicate the presence of reticular protein fibers in the extracellular matrix. Instead, the term reticular in the reticular layer refers to the net-like 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 resist forces in multiple directions and also to have elasticity in multiple directions. Now, although many of the fibers do have this net-like 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 reticular layer of the dermis. And those parallel orientations of many of the collagen fibers ultimately create these surgically relevant invisible lines. And those 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 allows for faster healing. And so the tissue will actually heal faster when the skin is cut parallel to cleave 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 a diagram of the integumentary system. And notice that only the reticular layer of the dermis is being colored here. And notice that the reticular layer of the dermis makes up the vast majority of the dermis, and 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's mostly made up of dense irregular connective tissue, which you can see right here those collagen and elastic protein fibers in this net-like arrangement. And so here we can label the collagen and elastic protein fibers. And, again, notice that there are plenty of accessory structures within the reticular 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, so it is vascular. And you can also see these yellow structures that you see here. Those are the lamellar or the Pacinian corpuscles, which are the pressure receptors that allow for sensations of pressure. And again, 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 lamellar corpuscles. Now, again, many of these collagen and elastic protein fibers can actually form parallel orientations that create these cleavage lines. And again, the cleave lines are invisible lines. And in this diagram we're only showing you the lines so that you can actually 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 reticular 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 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 dense irregular connective tissue is able to resist forces in 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 2nd 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 papillae? And we've got these 4 potential answer options down below. Now, recall that dermal papillae are these folded projections found in the papillary layer or the most superficial layer of the dermis, and they actually create folds in the epidermis as well called epidermal ridges. And together, these dermal papillae and epidermal ridges form friction ridges on the surface that are directly associated with our fingerprints. And so, without the dermal papillae, 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 papillae do have blood vessels. And so those blood vessels can help nourish the epidermal cells. However, the dermal papillae are not directly linked to the rate of healing. There are many different factors that come into the healing process. And so, option B is not the best answer option. Now, option C says their skin wouldn't be able to thermoregulate. Now, again, dermal papillae do have blood vessels that can undergo vasoconstriction and vasodilation for thermoregulation. However, thermoregulation of the skin is not unique to the dermal papillae because the reticular layer of the dermis that lies underneath also has blood vessels that can undergo vasoconstriction and vasodilation and help to thermoregulate 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 dermapapillae 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.