In this video, we're going to introduce our map of the lesson on cells of the immune system, which is down below right here. And so, we can go ahead and label the title of this map as "Cells of the Immune System". Now, what you'll notice is that all of these different cells of the immune system that you see down below right here are all derived from either a common myeloid progenitor cell or a common lymphoid progenitor cell. And of course, we know from our previous lesson video that the common myeloid and common lymphoid progenitor cells are derived from the hematopoietic stem cell found in the bone marrow.
Now, what you'll notice is that there are 3 major types of blood cells that are going to be differentiating from the common myeloid or the common lymphoid progenitor cells. And we've got those 3 major types of blood cells numbered down below. The first are going to be the red blood cells, which are also known as erythrocytes, and these red blood cells or erythrocytes are important for carrying oxygen gas or O2 throughout the blood and delivering oxygen gas to all of our tissues. And so, if you take a look at our image down below, notice that the red blood cells or the erythrocytes are over here on the far left-hand side, and once again, they're derived from common myeloid progenitor cells. And they are important for delivering and transporting oxygen gas to our tissues.
Now, the second major type of blood cells is going to be the platelets, and these platelets are specifically important for blood clotting. And so, they will help to create blood clots in very specific scenarios. And so, notice down below right here we're showing you the platelets, and so, those platelets are once again important for blood clotting, and they're derived from common myeloid progenitor cells.
Now, the third main type of blood cells are going to be the white blood cells. And the white blood cells are also referred to as leukocytes, and these are going to be the cells that are important for the host's immune system. And so, if we take a look down below at our image, notice that the white blood cells, the leukocytes are all of these other cells that you see right here. These are all leukocytes, white blood cells important for immunity. And so, moving forward in our course, these cells here are going to be the ones that we're focusing on as we talk more about innate immunity and adaptive immunity as well.
And, what you'll notice is that these white blood cells can be further divided into other groups. They can be further divided into two groups specifically, the granulocytes and the agranulocytes. So notice that the granulocytes are over here in yellow. Okay. So these are leukocytes that are further grouped as granulocytes, and they include neutrophils, eosinophils, and basophils. Then, what you'll notice is that these others over here are all agranulocytes, and so, because they are agranulocytes, they are grouped differently.
Now moving forward in our course, we'll be able to differentiate what granulocytes and agranulocytes are, and we'll get to talk about all of these different cell types in a lot more detail. But for now, notice that the leukocytes are grouped as either granulocytes or agranulocytes. Then, another thing that's important to note is that these granulocytes, as well as the monocytes, macrophages, dendritic cells, and natural killer cells, these cells that are highlighted here in yellow are all part of innate immunity. And the only two cell types that are listed here that are part of adaptive immunity are going to be the T cells and the B cells. And so notice that they have, next to their little name, they have this little tiny red star, and that little tiny red star here represents that they are part of adaptive immunity. So only these two cells here are part of adaptive immunity, the T cells and the B cells.
Another thing to note here is that these natural killer cells, T cells, and B cells, are all referred to as lymphocytes. And so the natural killer cells are lymphocytes that are part of innate immunity, and the T cells and B cells are lymphocytes that are part of adaptive immunity. Now much later in our course, we'll get to talk a lot more about these T cells and B cells and adaptive immunity. But moving forward in the next set of immediate videos, we're going to be focusing mainly on the cells that are part of innate immunity, which are the ones that are highlighted here in yellow. And so this here concludes our brief lesson on the map of our lesson on the cells of the immune system. And as we move forward in our course, we're going to be focusing once again on these white blood cells, these leukocytes, and we'll start off by focusing on the leftmost branches first, talking about the granulocytes, neutrophils, eosinophils, and basophils. Then we'll move on to talk about the monocytes, macrophages, and dendritic cells, and then we'll move on to talk about the natural killer cells. And once again, the T cells and B cells, we'll talk about when we're talking about adaptive immunity after we finish talking about innate immunity. And so, I'll see you all in our next lesson video.