Physical Barriers in First-Line Defenses: Mucous Membrane - Online Tutor, Practice Problems & Exam Prep

Mucous membranes are vital components of the innate immune system, consisting of epithelial cells and connective tissue that produce mucus via goblet cells. This mucus traps pathogens and prevents drying of tracts in the digestive, respiratory, and genitourinary systems. Mechanisms like peristalsis and the mucociliary escalator facilitate the movement of trapped microbes towards elimination. Peristalsis moves contents through the digestive tract, while the mucociliary escalator uses cilia to transport mucus and microbes from the lungs to the mouth for expulsion, ensuring effective defense against pathogens.

Mucous Membranes

This video, we're going to begin our lesson on mucus membranes, which, recall from our previous lesson videos, is one of the physical barriers in the first line of defense in innate immunity. Mucus membranes consist of an epithelial layer of cells and connective tissue that produces, as its name implies, mucus. Mucus is a slightly viscous glycoprotein fluid that is produced by goblet cells. These goblet cells are just cells that are going to produce components that are found in mucus. The mucus itself can protect and prevent line tracts from drying out.

Mucus membranes line our digestive tract, including our mouths, noses, esophagus, our entire digestive system, our respiratory tract including our trachea and lungs, and our genitourinary tract as well. It helps to protect and prevent those line tracts from drying out. Although our bodies do have mechanisms to protect the mucus membrane, some of those mechanisms we'll get to talk about later in our course. It turns out the mucus membranes are commonly used by pathogens to enter our bodies.

If we take a look at our image down below over here on the left-hand side, notice that we're showing you our map of the first line of defense in innate immunity, and we're focusing specifically on the physical barriers, specifically mucus membranes here in this video. On the right over here, we're showing you the mucus membranes diagram and notice that it consists of these epithelial cells and connective tissue and notice that the goblet cells specifically are going to be the cells that produce the components found in mucus. There is a mucus layer that is kind of lining, these mucus membranes. The mucus here can trap microbes, and the mucus can be washed out of the body and basically help to protect our membranes.

Here's a micrograph showing you an image of the mucus membranes as well. This here concludes our brief introduction to the mucus membranes, but as we move forward in our course, we'll be able to talk a little bit more about them and then apply the concepts that we've learned. I'll see you all in our next video.

Physical Barriers in First-Line Defenses: Mucous Membrane

This video, we're going to talk a little bit about peristalsis and the mucociliary escalator. Mucus membranes have mechanisms that can move microbes towards areas where they can be easily eliminated from our bodies. For example, moving microbes through our digestive tract towards the anus where they can be easily eliminated. Now peristalsis specifically refers to the intestinal tract muscle contractions that will contract and move food, liquids, and microbes that we've ingested towards the anus where they can be easily eliminated. The mucociliary escalator refers to the synchronized movement of cilia, which, recall from our previous lesson videos, are small hair-like projections that move like oars and can move substances through a system. The mucociliary escalator is the synchronized movement of cilia that move microbes out of the respiratory tract and towards our mouth.

The movement of these microbes is going to be once again away from our lungs, away from our respiratory tract and towards our mouth, where those microbes can be easily expelled from the body via coughing, sneezing, or we could swallow those microbes into our digestive tract where peristalsis can eliminate those microbes through the anus. Microbes that enter the nasal cavity can actually get trapped in what we refer to as the mucociliary blanket. The mucociliary blanket refers to ciliary cells in the nose and sinuses that are covered in mucus. Their job is to trap microbes that enter into our body and then to remove those microbes to make sure that they don't cause us any harm.

If we take a look at our image down below on the left-hand side, notice that we're focusing specifically on the first line of defense of innate immunity on the physical barriers, specifically talking about the mucociliary escalator. The mucociliary escalator somewhat resembles an escalator because microbes that are in the lungs can be moved towards the mouth and nose. You can see the movement of the mucus is in this direction, and this is because we have cells that have cilia that can move the mucus and the microbes that are embedded within the mucus towards our mouth and nose where we can easily eliminate those microbes in our mucus either through coughing, sneezing, or again, swallowing the mucus into our digestive tract where those microbes can be eliminated.

In our trachea, you can see the mucociliary escalator where we have mucus and foreign particles embedded within our mucus, and notice that these cells have cilia. These cilia can beat in a specific direction to move the mucus and move the foreign particles towards an area of interest. In this case, it's an escalator moving the mucus towards the mouth area and the nose area where, once again, they can be eliminated through sneezing, coughing, or swallowing the mucus so that it can be eliminated through our digestive tract.

This concludes our brief lesson on peristalsis and the mucociliary escalator and how they can help to eliminate microbes that have entered into the body and been trapped in the mucus membranes. We'll be able to apply some of these concepts moving forward and learn more as well. I'll see you all in our next video.

Which physical, nonspecific host defense mechanism is associated with the respiratory tract and trachea?

• A. Water-repelling keratin proteins.
• B. Lysozyme enzymes.
• C. Mucociliary escalator.
• D. Salivary amylase.

Here’s what students ask on this topic:

What are mucous membranes and their role in the immune system?

Mucous membranes are a type of tissue that lines various cavities in the body and covers internal organs. They consist of an epithelial layer and connective tissue, producing mucus via goblet cells. In the immune system, mucous membranes serve as a physical barrier in the first line of defense. The mucus they produce traps pathogens and prevents the drying out of tracts in the digestive, respiratory, and genitourinary systems. This trapping mechanism helps to prevent pathogens from entering deeper tissues and causing infections.

How do goblet cells contribute to the function of mucous membranes?

Goblet cells are specialized epithelial cells found within mucous membranes. Their primary function is to produce and secrete mucus, a slightly viscous glycoprotein fluid. This mucus plays a crucial role in trapping pathogens and particles, preventing them from penetrating deeper into the body. Additionally, the mucus helps to keep the mucous membranes moist, preventing them from drying out and maintaining their protective function. By producing mucus, goblet cells are essential for the effective operation of mucous membranes in the innate immune system.

What is the mucociliary escalator and how does it work?

The mucociliary escalator is a defense mechanism in the respiratory tract that involves the coordinated movement of cilia on epithelial cells. These cilia move in a synchronized manner to transport mucus, along with trapped microbes and particles, from the lungs towards the mouth and nose. Once the mucus reaches the mouth or nose, it can be expelled from the body through coughing, sneezing, or swallowing. This process helps to clear the respiratory tract of potential pathogens and debris, preventing infections and maintaining respiratory health.

What is peristalsis and its role in the immune system?

Peristalsis refers to the wave-like muscle contractions that occur in the digestive tract. These contractions move food, liquids, and trapped microbes through the digestive system towards the anus, where they can be eliminated from the body. In the context of the immune system, peristalsis helps to remove ingested pathogens and prevent them from colonizing the digestive tract. By facilitating the movement and expulsion of harmful microbes, peristalsis plays a vital role in maintaining gut health and preventing infections.

How do mucous membranes protect the digestive, respiratory, and genitourinary tracts?

Mucous membranes protect the digestive, respiratory, and genitourinary tracts by producing mucus that traps pathogens and particles. In the digestive tract, mucus prevents the lining from drying out and facilitates the movement of contents through peristalsis. In the respiratory tract, the mucociliary escalator moves mucus and trapped microbes towards the mouth and nose for expulsion. In the genitourinary tract, mucus helps to flush out pathogens and maintain a moist environment. These mechanisms collectively prevent infections and maintain the health of these vital systems.