The Integumentary System: The Dermal Layer

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  • 0:05 The Dermal Layer
  • 1:11 The Papillary Layer
  • 4:33 The Reticular Layer
  • 6:23 Hypodermis
  • 7:50 Lesson Summary
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Lesson Transcript
Instructor: Heather Adewale

Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.

Did you know that some people don't feel pain? Or that some always feel as if their skin is on fire? Learn about the causes of these diseases and the anatomy of the skin they affect in this lesson- the dermal layer of the skin.

The Dermal Layer

Did you know that a large amount of the dust in your home is actually dead skin cells? Pretty gross, right? All those dead skin cells fall off the surface of your skin as new cells are made in the top layer of your skin called the epidermis. Underneath that layer is a deeper layer called the dermis.

The dermis plus the epidermis make up the integument, or skin. The epidermis contains layers of cells that contain the protein keratin. These layers help protect the dermis. The dermis lies underneath the epidermis and contains most of the blood vessels and nerves that your skin needs to be healthy.

Both the epidermis and dermis are made up of layers of cells and tissue, as you can see here. But the dermis is a lot thicker than the epidermis, even though the dermis only has two layers and the epidermis has about five to six layers. That's because the cells in the epidermis are smaller and flatter, while those in the dermis are larger.

The Papillary Layer

The dermis actually contains different types of tissue, including loose connective tissue, elastic and collagen fibers, nerve cells, hair cells and sweat glands.

Loose connective tissue is pretty unorganized-looking - almost like someone took of bunch of cells and fibers, threw them up in the air and just let them drop, sort of like a game of pick-up-sticks or jacks, if you're old enough to remember the pre-video game days. It's characterized by a loose connectivity between cells and fibers, with lots of spaces in between. This tissue is found all over your body, mostly around your internal organs and blood vessels.

But let's get back to the skin. Here, it's found in the papillary layer of the dermis. This is the layer of the dermis closest to the epidermis. You know when your skin gets itchy and inflamed - a condition called dermatitis? Well, just as the name suggests, dermatitis is an inflammation of the dermis, specifically the papillary layer.

Now, look at the boundary between the epidermis and the papillary layer. See all those projections going upwards, like somebody poked the papillary layer? Those are called dermal papillae, and they help secure the dermis to the epidermis, kind of like how Velcro works, with all those spikes that interlock with each other. And the cool thing is the ripples from these projections can be seen on the skin of your hands and feet. That's what gives each person his or her unique fingerprints.

Okay, so the papillary layer's job is to connect the dermis to the epidermis. But that's not all it does. It also contains many tiny little blood capillaries (that's just the fancy term for really, really small blood vessels). These capillaries come up from deeper layers and supply the blood and nutrients for your skin. And, like the rest of your body, without blood, the skin would die.

Your papillary layer also contains another important set of structures for a properly functioning integumentary system: sensory nerve endings. These are receptors for the nervous system that relay the sensing of pain, temperature, touch and pressure information to the brain. In fact, without these structures, or with dysfunctional ones, you might have a condition known as CIPA, where you're unable to feel extreme hot or cold temperatures on your skin and even unable to feel pain! Or, if your nerve endings in your skin were overly active, you might have a condition known as fibromyalgia, which can make even the lightest touch painful.

While the sensors for light touch and temperature are located in the papillary layer, the pain sensors are actually located in the epidermis, while the pressure sensors, the ones that sense strong touch, are located further down, in the reticular layer.

The Reticular Layer

This layer lies underneath the papillary layer. So what makes the reticular layer different from the papillary layer? Well, the reticular layer is made up of a different type of tissue called dense irregular connective tissue. And, as the name suggests, it's denser than the loose tissue found in the papillary layer. That means it doesn't have as much space in between cells. It's a weave of collagen and elastic fibers that provide structural support for the skin. Both loose and dense irregular tissue are called irregular because when you look at them there is no apparent sense of organization.

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