 Today we're going to talk about hematology. Hematology is the study of the blood. The blood is specifically made up of three cellular components as well as plasma. Those three cellular components are the red blood cells, the white blood cells, and the platelets. You can see a picture of the this here over on the right side, the red blood cells. Obviously, you're the red in color of this skinning electron microscope photo. The white blood cells here are in blue. Those are varying sizes and shapes, and then you have the platelets here in yellow. All of these cellular components are suspended in plasma, which makes up about 55% of the total blood volume. The function of the blood is to transport oxygen, carbon dioxide, and nutrients to and from the body. When we're talking about red blood cells specifically, their anatomy shows a shape that is biconcave. This is seen as central pallor in a blood smear. As you can see over here, you have the white center with the darker red exterior. What this does is it gives the red blood cell a greater surface area that allows gas exchange to occur more readily. The lifespan of a red blood cell is approximately 120 days. This can be greater or less, depending upon other potential pathologies. Red blood cells get their energy from glucose, specifically from glycolysis, as well as the HMP shunt. And the hemoglobin molecule is the primary oxygen transport vehicle in the blood. We'll talk about that in just a few minutes. Talking about the formation of red blood cells and the cellular components is called hematopoiesis. As you will see here in this chart, there are many different types of cells that come from the one main multi-potential hematopoietic stem cell, or hematocytoblast. We're only going to focus today on one particular part of this chart as to not overwhelm you. So we're going to follow those hematoblasts down to the common myeloid progenitors. That common myeloid progenitor will give off the pro-erythroblasts, which will then continue on down to form the reticula sites. A reticula site is an immature red blood cell. This can be seen on a blood smear and then beyond that, it will turn into a erythrocyte, also known as a red blood cell. Of note, for the most part, all of these progenitor cells are occurring in the bone marrow. You will, however, see some reticula sites come out into the blood and that will be a particular pathology that we will talk about later.