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 and 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, and 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.

Then 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. It 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.

The papillary layer is a relatively small layer in the dermis. It is made up of areolar connective tissue, which, recall from our previous lesson videos, is a type of loose connective tissue. Areolar connective tissue is pretty much found underneath all epithelial tissue, including the epithelial tissue found in the epidermis. It's 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, and so it does have blood vessels.

Specifically, it has lots of capillaries, which are really small blood vessels. This allows for the delivery of nutrients to the epidermal cells that lie above. The papillary layer contains lymphatic vessels as well, which allows for immune cells to be transported. Immune cells can actually freely move through the loose areolar connective tissue to fight pathogens that may have made it through the epidermis. The papillary layer has these tactile corpuscles, also known as Meissner corpuscles, named after the scientist.

Corpuscles are really just small structures, and the term tactile is associated with touch. These tactile or Meissner corpuscles are nerve endings encapsulated in connective tissue that allow for touch sensations. These serve 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. In the papillary layer, there are also 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. These dermal papillae are folded projections that indent the epidermis and cause these epidermal ridges. Together, the dermal papillae and the epidermal ridges create what are known as friction ridges. These friction ridges are ridges 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. As their name implies, these friction ridges allow for increased friction that enhances our grip, and they also help to produce fingerprints.

Now, let's take a look at our image down below where we can piece some of these things together. Notice over here on the left-hand side, we're zooming in on the person's hand and focusing on the palm of the hand and the fingertips, which is made up of thick skin. The thick skin has a higher tendency to have these friction ridges. The friction ridges help to create the fingerprints, these unique patterns of fingerprints.

Now, 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 we're focused on the dermis. 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. Notice that only the papillary layer of the dermis is colored in this image. It lies immediately underneath the epidermis, and it is named for the presence of these dermal papillae.

The dermal papillae 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. The friction ridges ultimately appear on the surface of the epidermis. Notice here in green, we're highlighting just one of these dermal papillae. What you'll also notice is that in the papillary layer of the dermis are these Meissner corpuscles, or tactile corpuscles, which are shown here in yellow. Again, those are going to essentially be touch receptors, that allow for touch sensations.

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. Because the papillary layer only makes up a relatively small portion of the dermis, this means the dermis is going to be made up mostly of the reticular layer that lies immediately underneath. We'll talk more about the reticular layer of the dermis in our next lesson video. But for now, this here 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. 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. 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. The reticular layer actually makes up about 4/5ths or about 80% of the total amount of dermis, making it the largest layer of the cutaneous membrane, or the largest layer of the skin.

Because the reticular layer is the largest layer of the skin, it largely defines the properties of the skin. The reticular layer of the dermis is made up of dense, irregular connective tissue. Recall from our previous lesson videos that dense irregular connective tissue is characterized by having densely packed and irregular or random arrangements of mostly collagen protein fibers, but also elastic protein fibers in the extracellular matrix. This irregular or random arrangement of fibers allows dense irregular connective tissue to resist forces in multiple directions and to display elasticity in multiple directions as well. Thus, the dense irregular connective tissue gives those properties to the skin.

The skin can resist forces in multiple directions, is quite stretchy, and can have elasticity in multiple directions as well. The reticular layer also contains a variety of accessory structures, including some sweat glands and oil glands. It also has hair roots and pressure receptors that are called lamellar corpuscles, also sometimes referred to as Pacinian corpuscles. The term "lamellar" refers to the onion-like layers or the cinnamon bun-like layers that these lamellar or Pacinian corpuscles make. These receptors lie in the reticular layer of the dermis and serve as pressure receptors to allow for pressure sensations.

Recall that the term "reticular" means net-like, and in the reticular layer of the dermis, it refers to the net-like arrangement of mainly collagen protein fibers, but also some elastic protein fibers as well. 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. Because of this net-like or irregular random arrangement of these fibers, the skin can resist shrinking and forces in multiple directions, and also have elasticity in multiple directions.

Although many of the fibers have this net-like arrangement, it is important that there are also many fibers in the reticular layer of the dermis that may orient in one direction, in a parallel fashion to the surface of the skin. This creates what are known as cleavage lines, also sometimes referred to as tension lines. These cleavage or tension lines result from parallel orientations of many collagen fibers in the reticular layer of the dermis. These surgically relevant invisible lines 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. These lines are relevant to surgeons because when the skin is cut parallel to these cleavage or tension lines, it allows for faster healing.

Let's take a look at our image down below where we can piece some of these ideas together. Notice over here on the left-hand side, we have the diagram of the integumentary system. Notice that only the reticular layer of the dermis is being colored here, and notice that it 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, thus largely defining the properties of the skin. It is mostly made up of dense irregular connective tissue, which has 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. There are plenty of blood vessels here, making it vascular.

Notice these yellow structures here; those are the lamellar or Pacinian corpuscles, which are pressure receptors that allow for sensations of pressure. Although many of these collagen and elastic protein fibers form parallel orientations that create these cleavage lines, surgeons need to be very familiar with these cleavage lines because, when the skin is cut parallel to them, it allows for faster healing. And finally, notice here on the right, we have a leather jacket, which is important to note is made from the dermis of animal skins. The reticular layer makes up the vast majority of the dermis and is made up of dense irregular connective tissue, which can resist forces in multiple directions and have elasticity in multiple directions as well, properties we find in leather materials. This 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. 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 papilla and epidermal ridges form friction ridges on the surface that are directly associated with our fingerprints.

And so without the dermal papilla, 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 papilla do have blood vessels that can undergo vasoconstriction and vasodilation for thermoregulation. However, thermoregulation of the skin is not unique to the dermopapilla because the particular 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 derma papillae 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.

Here’s what students ask on this topic:

What are the two layers of the dermis and their functions?

The dermis consists of two layers: the papillary layer and the reticular layer. The papillary layer, which is more superficial, is made of areolar connective tissue and contains capillaries, Meissner corpuscles for touch sensation, and dermal papillae that create friction ridges. These friction ridges enhance grip and contribute to fingerprints. The reticular layer, which lies deeper, is composed of dense irregular connective tissue. It provides strength and elasticity to the skin and houses various structures such as sweat glands, hair roots, and Pacinian corpuscles, which are pressure receptors. Understanding these layers is crucial for grasping the skin's properties and functions, including healing processes related to cleavage lines.

What is the function of Meissner corpuscles in the papillary layer?

Meissner corpuscles, also known as tactile corpuscles, are specialized nerve endings encapsulated in connective tissue found in the papillary layer of the dermis. Their primary function is to serve as touch receptors, allowing for the sensation of light touch. These corpuscles are particularly abundant in areas of the skin that are highly sensitive, such as the fingertips and lips. They play a crucial role in our ability to detect fine textures and subtle changes in the environment, contributing to our sense of touch.

How does the reticular layer contribute to the skin's properties?

The reticular layer of the dermis is composed of dense irregular connective tissue, which includes a network of collagen and elastic fibers. This layer provides the skin with strength and elasticity, allowing it to resist forces in multiple directions and stretch without tearing. The reticular layer also houses various accessory structures such as sweat glands, sebaceous (oil) glands, hair roots, and pressure receptors like Pacinian corpuscles. These structures contribute to the skin's overall functionality, including temperature regulation, lubrication, and sensory perception.

What are cleavage lines and why are they important in surgery?

Cleavage lines, also known as tension lines, are invisible lines on the skin that correspond to the orientation of collagen fibers in the reticular layer of the dermis. These lines are surgically significant because incisions made parallel to cleavage lines tend to heal more quickly and with less scarring. This is because the skin's natural tension is minimized when cuts follow these lines, reducing the stress on the wound. Surgeons must be familiar with cleavage lines to optimize surgical outcomes and promote faster, more efficient healing.

What role do friction ridges play in the papillary layer?

Friction ridges are the raised patterns on the surface of the skin, primarily found in thick skin areas such as the palms of the hands and the soles of the feet. These ridges are formed by the dermal papillae in the papillary layer of the dermis. The primary function of friction ridges is to enhance grip by increasing friction between the skin and surfaces. Additionally, they contribute to the formation of unique fingerprints, which are used for personal identification. The increased surface area provided by friction ridges also aids in the sensory perception of touch.