In this video, we're going to talk about the first step in bacterial pathogenesis, which is exposure to the pathogen. And so once again, the very first step in bacterial pathogenesis is going to be exposure to the pathogen or an encounter pathogen that is going to result in an infection. This is because the pathogen not only must be encountered, but it must enter into the host tissues via what's known as a portal of entry. A portal of entry can be defined as specific locations where the host tissue cells are directly in contact with the external environment, allowing a pathogen in the external environment to enter into the body. Examples of portals of entry include the skin, mucous membranes, and parenteral routes, which involve the pathogen being directly injected into the body or the pathogen bypassing the skin and mucus and entering into the body via sites of broken protective barriers, such as cuts in our skin or open wounds.
The most common portal of entry for pathogens tends to be the respiratory tract, just being inhaled through our respiratory system. For example, the spread of COVID-19 mainly infects using a portal of entry of the respiratory tract. If we take a look at our image down below, we can see that there's an image here focused on the exposure to the pathogen. What you'll notice here is that Doctor Klutch is being exposed to the pathogen when this infected person sneezes or coughs. You can see that Doctor Klutch is going to be exposed to these pathogens. However, not all exposures are going to result in an infection. This is because the pathogen has to be able to enter via a portal of entry, like for example, perhaps Doctor Klutch's nose. Over here, what we are showing you is a zoom in of Doctor Klutch's nose. You can see that these microbes are entering via the portal of entry through the nose and the respiratory tract. Then, you can see the pathogen is now within Doctor Klutch's respiratory tract and is going to be exposed to the nasal mucus membrane.
This here concludes our lesson on the very first step in bacterial pathogenesis, exposure to the pathogen. We'll get to talk about the other three steps of bacterial pathogenesis as we move forward in our course. So I'll see you all in our next video.
