In this video, we're going to talk some more details about our skin. Recall that our skin serves as a physical barrier that's part of the first line of defense of innate immunity. Our skin is composed of 2 primary layers that we're going to discuss. The first layer is the epidermis, and the second layer is the dermis. The epidermis is the outer surface layer, composed of many layers of epithelial cells. The outermost layer of the epidermis consists of dead skin cells containing a water-repelling protein called keratin. This protein, found in hair and nails, helps create a dry environment on our skin, which can prevent some microbial growth. While some microbes are capable of tolerating dry environments and can grow on our skin, others cannot, which prevents their growth on our skin.
In addition to keratin protecting us from some microbial growth, our skin also sheds. The shedding of the outermost layers of the epidermis helps remove microbes on the skin by taking those microbes along with the shedding skin. These are protective features to help protect us from microbes. The second layer of the skin, the dermis, is much thicker than the epidermis. It is composed of connective tissue, making the dermis extremely durable and very tough to break, which also helps prevent microbes from penetrating our skin.
We're also going to focus on the skin as a physical barrier, specifically as part of the first line of defense of innate immunity. Notice that microbes are capable of growing on our skin. However, the keratin in the outermost layer of the epidermis can help create a dry environment to limit the growth of some microbes. Moreover, the outermost layer of our skin will shed, which also removes microbes along with it. Beneath the epidermis is the dermis which consists of connective tissue, enhancing its durability and toughness. Again, these features help prevent microbial penetration.
Beneath the dermis is a layer of fat tissue called the subcutaneous layer that contains blood vessels. You can see the connective tissue and fat below that. Ultimately, the main point of this video is to show that the skin serves as a physical barrier that's part of the first line of defense of innate immunity and can prevent microbes from penetrating our body. This concludes our brief lesson on the skin, and we'll be able to learn more and apply these concepts as we move forward. I'll see you all in our next video.