 This is the thymus gland and although in our curricula it doesn't get the same amount of love as the other glands, we're gonna see why it's one of the most important glands in our body. First of all, notice the thymus gland is located between the lungs somewhere slightly above the heart. It also has a couple of lobes. Let's zoom into it. This is what it will look like and I like to think of the thymus gland as sort of a school. A school for what exactly? Well, if we look inside the gland, we will see it's mostly made of two types of cells. The first type of cells I've shown over here, these are called the thymus epithelial cells, which for short we'll just write as TECs, thymus epithelial cells. I like to think of this as sort of like the structure, it's part of the structure of the school. So it forms the floor, the ceilings, the benches, the walls, and everything around it. And then we have the students inside this school. These, you know what these are? These are the immature, immature T cells. These are one of the important cells of our immune system. These T cells are actually formed inside our bone marrow and then they find their way into our school, into our thymus. Inside the thymus, they undergo a rigorous training process where they understand the difference between our own body cells and the foreign cells, which is super, super, super important. And through understanding the difference, they become mature. And that's the reason why I like to think of thymus as a school because it helps in maturing these immature T cells formed inside the bone marrow. And once they become mature, these T cells, mature T cells, can have different professions. Some of these T cells, which are matured, become helper T cells. Their job would be to go and activate other immune cells. Then there are these other kinds of T cells that can directly go and attack the foreign substances. Then there are some other kinds of mature T cells that help in remembering what the attack was so that the next time if the same attack happens, it becomes super easy to help eradicate it. And although this maturation process is very complex, one of the things that actually helps in maturing is a hormone that is released by the epithelial cells. So these hormones, they act on these immature T cells and along with a bunch of other things, it helps them mature and differentiate. Differentiate means just take different different professions, different different jobs. And this hormone that the TCs produce, we give a name to that, these are called thymosins. Now thymosins is not a single type of hormone. It's a class of hormone. There are thymosins alpha, thymosins beta and so many other things. But what I find interesting about thymosin hormone is that they have a very local effect. Look, the thymosin hormone is produced by the thymus and its effect is inside the thymus itself. If you've studied the hormones produced by other glands, usually the hormones go into the bloodstream and then they have effects on organs that are far away, cells that are far away. But thymosins effect is usually inside the thymus gland itself. Their receptors are primarily found in these immature T cells itself. So they have a very local effect. In some sense, that makes thymosins a little unique hormone. Now it turns out that some of the thymosins also do enter into the bloodstream and they do tend to have some other functions as well, like the help in repairing and healing of our wounds and all of that. But but there's still more for us to explore over there. But in short, the primary function of thymosin is to help these immature T cells become mature and differentiate so that they can form a part of our strong immunity system. And so thymos acts like a school, an extremely important school for our body.