Pancreas: Study with Video Lessons, Practice Problems & Examples

The pancreas is a vital glandular organ that produces pancreatic juice, containing enzymes like amylase, proteases, lipases, and nucleases, which aid in the digestion of carbohydrates, proteins, fats, and nucleic acids, respectively. It releases these inactive enzymes into the duodenum, where they become active, preventing self-digestion. The pancreatic juice also includes bicarbonate, which neutralizes the acidic chyme from the stomach, creating an optimal environment for enzyme activity. Understanding the pancreas's structure and function is crucial for grasping the digestive process and maintaining homeostasis.

Pancreas

All right, folks, it's now time to focus on the pancreas. We can orient ourselves to our image here. We see this sort of longish yellow organ here kind of tucked right up against the small intestine, that first section of the small intestine, the duodenum. And we'll look at that anatomy in more detail coming up. Right now, we want to focus on what it is that the pancreas is producing. What is it that it's putting into the duodenum to aid in chemical digestion? Alright. So we're going to start by saying the pancreas is a glandular organ that produces enzymes and hormones. Now those hormones, however, are part of the endocrine system, so we'll deal with that there. These enzymes, that's what we want to focus on because that's what's going to aid in chemical digestion. Now those enzymes are released as part of the pancreatic juice, and the pancreatic juice is going to be a mixture of water, inactive enzymes, and bicarbonate. Now I just want to note when I say water, it's actually a fair amount. Over 1 liter of pancreatic juice is produced every single day. So every single day, you're producing more than this soda bottle's worth of pancreatic juice and putting it into that small intestine. Now considering that the pancreas is something like less than a quarter of the size of this soda bottle, that strikes me that it's producing a lot of liquid. Alright. The chief thing in that liquid that we want to talk about though is that it is releasing as part of it, these inactive enzymes that become active in the duodenum. Alright. Inactive enzymes that become active. Remember, that's reminiscent of what happened in the stomach. Remember, in the stomach, we had pepsin, that enzyme that digested protein, but it didn't become active until it was mixed in with the chyme. Same thing here. These enzymes in the pancreatic juice, they digest large biomacromolecules. But that's what you are made of. Right? So you don't want to digest yourself. You don't want to digest your own pancreas. So they are released as inactive enzymes and only become activated when they're mixed in with the chyme with those food molecules. We're going to say here that that prevents the pancreas from digesting itself. Alright. So now let's look at this composition of this pancreatic juice. Let's see what's really in there. So we have this Erlenmeyer flask here filled with pancreatic juice. We can see the molecules in there. It has this little warning pancreatic juice label on it. So let's see what's actually in there. First, well, we mentioned bicarbonate. Bicarbonate is going to make this pancreatic juice alkaline, and that is going to neutralize the chyme. So the chyme is coming in from the stomach, so it has that really low pH from the gastric juice. This is going to make that more neutral. It's going to allow the enzymes to be active, and it is also going to protect the small intestine. Alright. Now we have 4 other things here, and these 4 other things are enzymes that digest our 4 major classes of biomacromolecules. First off, we have amylase. Amylase is an enzyme that digests starches. So we digest starch into smaller molecules that will eventually get broken down even more into those simple sugars, which can be absorbed in the small intestine. We're going to have proteases. Proteases digest protein. Now we're going to release a few proteases, but I want to call one out. We release trypsinogen, which gets activated into the enzyme trypsin. Now I'm calling this one out because trypsin's job is, well, like other proteins, to digest the proteins in your food, but it also activates the other enzymes. So trypsinogen gets released and there's an enzyme in the small intestine that converts that to trypsin. That trypsin then goes breaking down the proteins in your food and turning on your other enzymes. Alright. One of those enzymes it is going to turn on is going to be a lipase. Well, there are actually a couple of lipases in there. A lipase will digest lipids, the fats in your foods. And lipase, well, we had some lipase that was released in the stomach as well, but in the pancreatic juice, that's going to really be the main source of the lipases. This is really where you get your lipases for digesting the fats in your diet. Alright. Finally, we have nucleases, and nucleases digest nucleic acids. Now you may not think of things like DNA and RNA as being nutrition in the food you eat, but it's there and you break them down. Now there's not a lot of DNA and RNA compared to these other molecules that you're digesting, but you do break them down. You absorb those sugars from the backbone of the DNA and RNA, and you absorb those bases as well. Alright. So that's what the pancreas makes. We're going to focus on its structure, its anatomy next. Before we get there, we got practice and examples. I'll see you there.

Pancreas Example 1

Example tells us that listed below are the enzymes found in pancreatic juice and some different food items. We want to write the letter on the line next to each food to indicate which enzymes you would expect to be active in digesting it. Note some foods may require multiple enzymes and not all foods will be digested by the pancreatic juice. Alright. So we have 4 enzymes or classes of enzymes here. We have amylase, lipases, nucleases, and proteases. Let's quickly remember what each one of these digests. So do you remember what amylase digests? That's going to be starch, lipases. Lipases digest lipids or fats, nucleases digest nucleic acids, DNA or RNA, and proteases. Now that's going to digest protein. Right? Alright. So let's go through these foods and think what things are going to be in these foods. Alright. Let's start with a good old steak. Alright. When you think of steak, what's the main nutrient there that you probably think of? I think of protein. So I'm definitely going to put a protease on the line here. Protease is definitely active in breaking down that steak. What else? Well, any good steak has some marbling in it. That fat mixed in. So for that, you are going to need lipases. So I'm going to put a b on the line here. Anything else? Well, that steak is muscle cell, and so in those cells, there's definitely DNA and RNA. So you're going to need these nucleases. So I'm going to put a c on the line as well. Anything else? Well, in those cells, there probably is some starch, and you can break it down using that amylase. But I'm going to leave that off because, really, the majority of what you're going to have here are these other macronutrients. So I'm going to say d, b, and c, and be done with the steak for now. Alright. What about ice cream? Well, what's the major macronutrient that you think of when you think of ice cream? Well, there are kind of 2 that I think of. The first one though, I think of fat. And so for fat, what enzyme am I going to need? Lipases. So lipases will digest that fat in that ice cream. What else? Well, then I think of sugar. Right? Nice and sweet. Do we have enzymes here, though, that digest sugar? We don't. Right? Amylase digests starch and breaks it down into sugars, but it's actually going to be enzymes in the brush border in the lining of the small intestine that actually break down those sugars into the into the smallest molecules that can be absorbed. So we're not going to use any amylase for ice cream. Well, anything else? Well, there is a little bit of protein in the ice cream. Now it's alright, I think, if you leave that off though. So I'm just going to put this in parentheses. I'll put proteases because there is protein in ice cream. Alright. Now what about an apple? All right. Well, when I think of an apple, the first thing I think of is that sweetness. And that sweetness, again, is going to be sugar, and we are not going to have enzymes here to digest sugar. There are going to be other enzymes that we need, though, specifically apple. That's going to definitely have some starch in it. So we're going to use, I'm going to put down this a for amylase for the starch in the apple. Apples get sweeter as the starch gets broken down into sugars, but there's still going to be starch in an apple. Well, anything else? Well, in apple, there are whole cells, and so if there's whole cells, there's going to be DNA and RNA. So I'm going to put a C here as well. Alright. What about lipases and proteases? Alright. Well, again these are whole cells. So yes. Absolutely. Technically, there are going to be some fats, like in the cell membrane. There are going to be proteases, that be I'm sorry. There are going to be some proteins in there because they are cells that make up the apple, but when we're thinking about this for the main things that in there, I'm going to leave those off because there isn't going to be a lot relative to the other things here. Alright. What about rock candy? Or, and that rock candy is going to be made of sucrose. Well, sucrose has purified sugar, and we don't have any enzymes here to digest sugar. And there isn't anything else really in it for these macronucleases be I'm sorry. Macromolecules because it's a purified sugar. So I don't think it really can be digested by these pancreatic enzymes in this pancreatic juice. Alright. Well, that brings us to French fries. Good old French fries. What do you think for that one? Well, when I think of French fries, I think of potatoes, and those are definitely starchy. So you're definitely going to use amylase to break down that starch. I also think of fat. Right? A good french fries fried in some oil. So I'm going to need lipases to break down that fat. Anything else? Again, whole cells in a potato. There's going to be some DNA and RNA there. So I'm going to put c for nucleases. Now again, technically, if there's whole cells, there's going to be some proteins in there, but compared to everything else, it's going to be less. So I'm going to leave it off for now. Alright. With that, I've answered the question. We got more practice after this. Give it a try.

Which product of the pancreas is correctly matched to its function?

• A. Amylase: digest sugars.
• B. Proteases: breaks down lipids.
• C. Nucleases: digests nucleic acids.
• D. Bicarbonate: lowers the pH of pancreatic juice.

What may be one reason that many of the enzymes in pancreatic juice are inactive in the pancreas, only to be activated once they enter the small intestine?

• A. Protects the enzymes from degrading.
• B. Decreases the total amount of enzymes needed.
• C. Allows the digestion process to happen faster.
• D. Prevents enzymes digesting tissues of the pancreas.

Anatomy of the Pancreas

Now that we understand what the pancreas produces, that pancreatic juice, we want to talk about the structure of the pancreas. So first, we'll talk about the gross anatomy of the pancreas, and then we'll focus on the microscopic anatomy. Alright. For the gross anatomy, let's orient ourselves to our image here. We see the pancreas, that sort of long yellowish organ there, and we see the small intestine kind of wrapped around one end of it there, specifically that first section of the small intestine, the duodenum. And running in front, that green duct there, that's going to be the bile duct. Alright. So for the gross anatomy, there isn't a lot to distinguish the different parts of the pancreas, but we do give the different regions names just so that we can refer to them specifically. We're going to start with the tail, and we'll highlight that there in orange. The tail, we're just going to say, that's the pointy end. The pointy end is going to be lateral. It’s sort of sticking off to the left side of your body, tucked under the stomach there. Well, if the tail is the pointy end, then the head, well, the head is going to be the round end on the other side. The round end that's medial, again, kind of tucked up against the small intestine there, and it's going to be wider and rounder than the tail. In between, well, between the tail and the head, you find the body. The body is going to be that middle section in the middle. Now again, there isn't really much structurally different between these, and there aren't hard and fast lines between the head, tail, and body. And sometimes people refer to the neck of the pancreas as well. We don't have it here because it's not always referred to, but you can figure out where it is. The neck would be the space between the head and the body. There you go. Alright. The other, well, really, the main structure that you're going to notice on the pancreas here is that main duct that's running down the middle of it. There, we've highlighted in orange. That's the pancreatic duct. This is going to be the main central duct of the pancreas. That pancreatic juice is going to travel down so that it can enter into the small intestine. Now, I also just want to note there is another duct on this drawing, so we want to call it out. The second duct that you see is the accessory pancreatic duct. Now there's a good chance you're not going to be responsible for the accessory pancreatic duct, though, because it's not always present. Not everybody has one, and people who do have one, sometimes it's in different places. We want to call it out because it is on this drawing, and for some people, that's another way that pancreatic juice can get into the small intestine. Alright. So that's our gross anatomy. Let's focus on the microscopic anatomy. Alright. So this is our image for the microscopic anatomy. You can see here the pancreas is made up of all these sort of little balls or clusters of cells connected by these dots running through the middle. So those clusters of cells, we're going to call the acini. Right? The acini are going to be these clusters of secretory cells, and we'll highlight one here. So this would be one acinus and many acini. So this acinus has these secretory cells, and the individual cells we are going to call, well, here's one acinar cell. So these acinar cells in the acini secrete these inactive digestive enzymes. Remember, the pancreatic juice is filled with digestive enzymes, but they don't actually get turned on until they make it to the small intestine because we don't want those digestive juices digesting the pancreas itself. Alright. Well, those inactive digestive enzymes get released by the acinar cells into the ducts. So we can see here, this is a duct. And all of these ducts are going to run together, and they're going to transport the secretions to that central pancreatic duct. All right. So all these ducts run, carry those enzymes to the pancreatic duct so that they can make it into the small intestine. But lining these ducts, we have also duct cells. So these duct cells line the ducts, and these are also going to have secretions. In terms of the pancreatic juice, these duct cells, they make the juice. Alright? These secrete the water and also the bicarbonate. Alright, the water. Remember, we said the pancreas makes over a liter of pancreatic juice a day. So this is a one-liter bottle. This is something like ten times the size of the pancreas. So these duct cells are releasing a ton of liquid over the day that go into the small intestine. Now along with that liquid, there's also bicarbonate. Remember, that bicarbonate is alkaline. It raises the pH, and that is there to neutralize the chyme because it's going to be mixing with the chyme in the small intestine, and that chyme will have just come from the stomach, and it'll be that really low pH because it has that stomach acid in it. Alright. So that's the gross anatomy. That's the microscopic anatomy. We're going to look at all the different ducts that connect the pancreas, the gallbladder, the liver to the small intestine. We're going to look at all that stuff next. It's going to be a good time. I'll see you there.

Pancreas Example 2

In this example, it says that a patient with pancreatic cancer undergoes an operation to remove a tumor on the tail of the pancreas. During the operation, approximately one third of the pancreas is removed. Alright. So for a, it says on the diagram, circle the approximate region that was removed as part of the surgery. So here's our diagram. We see the pancreas, and we see the small intestine that it's up against here, that first section of the small intestine, the duodenum. Alright. So if one third of the pancreas is removed and it's on the tail of the pancreas, what are you circling? Well, I'm circling this region down here. We said the tail was sort of the pointy end farther away from the small intestine. So if you're removing a third of the pancreas at the tail, that's about what I circled there.

Now b here says, would you expect a surgery to remove the head or the tail of the pancreas to be more complicated? And explain why. So which do you think would be a more complicated surgery, removing the head or the tail? Well, I think the head would be more complicated, and we can see why if we look at our image here. Right? So if we look over at our image, we have this pancreatic duct and the pancreatic duct enters into the small intestine. So if you're going to have a surgery, removing the head of the pancreas, well, you have to figure out how you're going to connect the rest of this pancreatic duct to the small intestine. Alright. So therefore, the head, I think, is going to be more complicated, and we're going to say here, that's because the head connects to the small intestine via the pancreatic duct. Removing the tail of the pancreas, the pancreas is still connected to the small intestine, so the rest of the pancreas, if it's still functional, is still going to be secreting those juices that can enter into the small intestine. Alright. Obviously, if this is a test question, I'd write it in nice complete sentences.

Now c here says, after such surgery, some patients require additional digestive enzyme supplements. Based on where in the digestive system different enzymes are produced, which class of digestive enzyme would you expect is the most important to supplement? Alright. Well, when we think about the pancreas, we said it's making, basically, enzymes that digest all of the macromolecules in your food. Right? The proteins, the lipids, the nucleic acids, and the starches. But which one do you think would be most important to supplement? Well, you might want to supplement them all, but we did note that lipases, this is the primary source of lipases. So pancreatic juice makes most of the lipases. So I am going to say that the lipases are what you would most want to supplement. Alright. With that, we've answered the question, and we got practice problems after this. I'll see you there.

Which pair below correctly matches the cell type with their secretion?

• A. Duct cells: proteases.
• B. Duct cells: bicarbonate.
• C. Acinar cells: water.
• D. Acinar cells: bile salts

The clusters of secretory cells in the pancreas are called:

• A. Ducts.
• B. Lobules.
• C. Acini.
• D. Paneth cells.

Here’s what students ask on this topic:

What enzymes are produced by the pancreas and what are their functions?

The pancreas produces several key enzymes that aid in digestion. These include amylase, which digests starches into simpler sugars; proteases, such as trypsin, which break down proteins into amino acids; lipases, which digest fats into fatty acids and glycerol; and nucleases, which break down nucleic acids like DNA and RNA into their component nucleotides. These enzymes are released in an inactive form and become active in the duodenum to prevent the pancreas from digesting itself.

How does the pancreas prevent self-digestion?

The pancreas prevents self-digestion by releasing its digestive enzymes in an inactive form. These inactive enzymes, such as trypsinogen, are only activated when they reach the duodenum and mix with chyme. This activation process ensures that the enzymes do not digest the pancreatic tissue itself. Additionally, the pancreatic juice contains bicarbonate, which neutralizes the acidic chyme from the stomach, creating an optimal environment for enzyme activity without damaging the pancreas.

What is the role of bicarbonate in pancreatic juice?

Bicarbonate in pancreatic juice plays a crucial role in neutralizing the acidic chyme that enters the duodenum from the stomach. This neutralization raises the pH of the chyme, creating a more alkaline environment that is optimal for the activity of pancreatic enzymes. By doing so, bicarbonate helps protect the lining of the small intestine from the corrosive effects of stomach acid and ensures efficient digestion and absorption of nutrients.

What is the gross anatomy of the pancreas?

The gross anatomy of the pancreas includes three main regions: the head, body, and tail. The head is the rounded, medial end that is nestled against the duodenum. The body is the central portion, and the tail is the pointed, lateral end that extends towards the left side of the body, under the stomach. The pancreas also contains a main pancreatic duct, which transports pancreatic juice to the small intestine, and sometimes an accessory pancreatic duct, which may also carry pancreatic juice.

What is the microscopic anatomy of the pancreas?

The microscopic anatomy of the pancreas consists of clusters of secretory cells called acini. Each acinus contains acinar cells that produce inactive digestive enzymes. These enzymes are transported through a network of ducts lined with duct cells, which secrete water and bicarbonate to form pancreatic juice. The ducts converge into the main pancreatic duct, which delivers the pancreatic juice to the duodenum. This intricate structure ensures the efficient production and delivery of digestive enzymes and bicarbonate.