 Let's explore how pancreas help in maintaining our blood sugar level. If you were to zoom into a small section of the pancreas, you'll find cells like this. You will see a lot of cells like these which can secrete into these ducts. Such cells are called exocrine or such cells are part of the exocrine system. Exocrine system is when you have ducts like these and turns out that majority of your pancreas is basically the exocrine cells. So about 95 to 96% of your pancreas is made of such exocrine cells. But in the ocean of these cells, we will find tiny islands like these which do not secrete into a duct, which secrete directly into the bloodstream, which means they will give out hormones. These are the cells of the endocrine system and you'll find these islands all over your pancreas. And it's for that reason they are named the islands of Langerhans. They're actually called islets which basically mean islands and Langerhans because that's the name of the person Paul Langerhans who discovered these two kinds of cells. Which means pancreas have both the endocrine and the exocrine system. The exocrine is the majority. The endocrine is just like one or two percent of your pancreas. But it's this endocrine system that's responsible for maintaining your blood sugar level. So how do they do that? Well before the how, let's think about the why. Why do you need to maintain a particular sugar level in your blood? Well if the blood sugar level is too low, then your cells will not be able to absorb enough sugar and get enough energy. You need sugars for energy. So too low sugar is bad. But what if you have too high sugar? That shouldn't be a problem right? Hey that's a problem as well. Turns out too much sugar in the blood can actually damage your blood vessels. And you don't want your blood vessels to get damaged. It can cause all sorts of problems in your body. So it's important to maintain your blood sugar level. So how does it do that? Well imagine you just ate this delicious cake and suddenly the blood sugar level has increased above normal. So what happens? Well these cells that you find in that is colored yellow over here which are called the beta cells. These cells will now secrete a hormone directly into the blood capillaries. These are the blood capillaries. You can imagine the pipes coming out of the screen over here. And the hormone that it secretes into the blood capillaries is insulin. And insulin's job well is to lower that blood sugar level. How does it do that? Well insulin is a hormone which means like any other hormone it goes into your blood and then it's circulated to all the cells. And then the cells that have the receptors the insulin binds to those cells and does something to it. So it turns out that the insulin receptors are majorly found in your muscle cells. Muscle cells. They're found in your fat cells. And they're found in your liver cells as well. Liver cells. So you know what they do? They basically the insulin basically asks these cells to start taking up more sugar from the blood so that it can lower the blood sugar level. And this kind of makes sense to me. Your muscle cells absorbing the sugar so that gets energy to do all the activities that we need to do. Your fat cells and liver cells you know why they would want to absorb this blood sugar? To store it for whenever we would need it later. Your fat cells can convert glucose to fat. Whereas your liver cells will convert glucose to glycogen. And this is basically how insulin from the beta cells are going to lower your blood sugar back to the normal range. But there are certain cells in your body that don't need the insulin to tell them. Like the neurons of your brain. They don't need the insulin to tell them. Whenever they want they will absorb the sugar from the blood. I want you to think a little bit about why is that the case? Ponder upon it. It's for you to think a little bit about this. Maybe discuss with your friends and all of that. Anyways, what if insulin is not working in your body? Well then your blood sugar levels can stay dangerously high. This condition is called diabetes. And this can happen either because your immune system can destroy the beta cells itself. Thinking that it's a foreign substance. Not understanding it's the part of your own body. Or sometimes your beta cells are fine. But your target cells of the insulin they're just resistant to it. In either cases that's a problem. And one of the common solutions is to have an insulin shot. And to monitor the blood sugar level closely all the time. All right now let's look at the opposite situation. Imagine you're starving for a long time. Your blood sugar levels have gone really low. What happens now? Well now these pink colored cells. But they're not really pink in color. But the ones that are shown pink in color. Which are called the alpha cells. Alpha cells. They now are going to secrete a hormone called glucagon. Glucagon. What do they do? Well the exact opposite of what insulin did. Their job is to increase your blood sugar. Their target cells are mostly the liver cells. Why? Because glucagon just tells the liver cells to do the exact opposite. To break down the glycogen that is the stored glucose. Break down the glycogen and give glucose. Break glycogen and give glucose and put that glucose into back into the blood. It also asks the liver to produce glucose from other sources. We give a name to such process. It's called gluconeogenesis. Remember that? Glucogenesis means creating glucose. Neo means from other sources. Like from amino acids for example. Why is this important? Because what if your glycogen reserves are low? Your body basically says hey get me glucose from glycogen if it's available. But also get me glucose from other sources. Like do both and give me glucose and put it in the blood and increase the blood sugar level. So this is how by using insulin and glucagon your pancreas can maintain the blood sugar level. Now if you are curious you might also see some other cells. Some green cells and some blue colored cells over here. What are they you might be wondering? Well they are called gamma and delta cells. Pretty pretty amazing naming system. What do they do you might be wondering? Well their job is actually to regulate the secretions of both the endocrine and the exocrine system. What I mean is one of them. I don't remember which and it's not really all that important for us. But one of them are going to regulate the insulin and the glucagon productions. And the other one is going to regulate the secretions produced by the exocrine cells. And that's why they are low in number. And that's why when it comes to regulating blood sugar the majority of the work is done by the beta and the alpha cells themselves. Finally before we leave I have a couple of curious questions for you. You see that there are a lot more of beta cells compared to alpha cells. Why is that the case? What would have happened if it was the other way around? We had more alpha cells and beta cells. Secondly you can see that beta cells are in the core but the alpha cells are on the periphery. Why is the structure that way? Again what would have happened if it was the other way around? Alpha cells in the core and the beta cells in the periphery. Is this just a random evolutionary consequence? Or is there an advantage to having such a structure? So ponder upon these questions because it's these kinds of what-if questions that you should keep asking and you should keep pondering upon to learn biology deeply.