In this video, we're going to begin our lesson on the skin, which serves as a physical barrier in the first line of defense of innate immunity. And so really, there are two primary types of physical barriers of the first line of defense in innate immunity. The first is going to be our skin, and the second is going to be our mucous membranes. Now first, we're going to talk more about the skin as a physical barrier, and then later we'll talk more about mucous membranes as a physical barrier. Now epithelial cells are important here because these are tightly packed skin cells that line the surfaces, or the perimeter of the body. And so, if we take a look at our map down below over here, notice that the first line of defense is specifically the physical barriers are being colored and highlighted here, and this includes our skin as well as our mucous membrane. And so moving forward, we'll first talk about the skin, and then we'll talk about the mucous membranes later. And so notice everything else here is all grayed out because we're going to be talking about them in separate videos later down the line. But for now, we're talking about the first line defenses, primarily the physical barriers including the skin and mucous membranes. And so I'll see you all in our next video to talk more about them.
Physical Barriers in First-Line Defenses: Skin - Online Tutor, Practice Problems & Exam Prep
The skin acts as a crucial physical barrier in the first line of defense of innate immunity, composed of two layers: the epidermis and dermis. The epidermis, featuring dead skin cells rich in keratin, creates a dry environment that inhibits microbial growth. Additionally, the shedding of skin helps remove microbes. The thicker dermis, made of durable connective tissue, further prevents pathogen penetration. Together, these layers protect the body from harmful microbes, emphasizing the skin's vital role in maintaining homeostasis and immune defense.
Physical Barriers
Video transcript
Skin
Video transcript
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.
Which of the following sheds dead cells along with microbes attached to those cells?
Epidermis.
Dermis.
Hypodermis.
Mucous membrane.
Hair follicles.
Examples of 1st line defenses to infection which are components of the innate immune system include all of the following except?
Unbroken skin.
Phagocytosis of a pathogen by an immune cell.
Digestive enzymes in saliva.
Destructive acids in gastric juices.
Naturally occurring human microbiome.
Why is keratin an important layer of defense against infection?
Keratin is hydrophobic which keeps the skin & hair dry which decreases microbial growth.
Keratin is the top layer of skin that regularly flakes off, removing microbes from the skin’s surface.
Keratin is the main component of the dermis making it hard to tear which decreases infections from wounds.