So, here we have an example problem that asks which cell types in the epidermis are responsible for preventing a pathogen from entering the body and causing infection? And we've got these 4 potential answer options down below. And so recall from our previous lesson videos that there are 4 main types of cells found in the epidermis or the outermost layers of our skin. And those 4 main types of cells are keratinocytes, melanocytes, dendritic cells, specifically Langerhans cells, and tactile epithelial cells or Merkel cells. And so what you'll notice is that 3 of these options mention tactile epithelial cells.
And recall that these tactile epithelial cells, their main function is to work with nerves to allow for touch sensations. And they're found toward the bottom of the epidermis in the deepest layer of the epidermis. And so, these tactile epithelial cells, their main function is not to protect and prevent a pathogen from entering the body and causing infection. And so, for that reason, we can actually eliminate options B, C, and D. And of course, this leaves us with answer option A.
Which says keratinocytes and dendritic cells. Now, recall that keratinocytes are going to make up about 90% of all of the epidermal cells. And so, they make up the vast majority of the epidermis. And these keratinocytes, as their name implies, they create keratin which recall is a tough fibrous water-resistant protein that gives the epidermis protective properties and allows it to serve as a very good barrier to things in the environment such as microbes, for example. And recall that the dendritic cells, specifically Langerhans cells are immune cells that actually help to activate the immune system.
And so, together these keratinocytes and dendritic cells can help to prevent a pathogen from entering the body and causing infection. And so option A here is the correct answer to this example. That concludes this example and I'll see you all in our next video.