The Gallbladder: Study with Video Lessons, Practice Problems & Examples

Bile, produced by the liver and stored in the gallbladder, plays a crucial role in fat digestion. It contains bile salts, which emulsify fats, increasing their surface area for enzyme action. The release of bile is triggered by the hormone cholecystokinin (CCK) from the small intestine. Additionally, bilirubin, a waste product from heme breakdown, gives bile its color and contributes to feces' brown hue. Without bile, fats remain undigested, leading to fatty, grayish feces. Understanding bile's function is essential for grasping the digestive process and maintaining nutrient absorption.

Gallbladder and Bile

As we continue talking about digestion, we now want to focus on the role of bile. When we talk about bile, we also need to talk about the gallbladder. That's because the gallbladder is going to be this small muscular sac that's just inferior to the liver, but its function is to store bile. And that bile is actually produced by the liver. So let's orient ourselves to our image here. You can see the liver on top there, that sort of big reddish-brown organ, and then just underneath it, you see that green kind of pear-shaped organ. That's the gallbladder. Now in our image, you also see these dots or these tubes in green connecting the liver and the gallbladder, and both of them to the small intestine there, that first section of the small intestine, the duodenum. In our image, we also see in yellow the pancreas. We're not going to talk about the pancreas here. We just have it there for reference. All right. So let's focus on these ducts. The first one that we want to look at is going to be the cystic duct. The cystic duct, we've highlighted there in blue and labeled it a, this connects the gallbladder to the bile duct, and we'll talk about the bile duct next. But you can see this is just one tube, one tuck duct that leads up to the gallbladder. This means that for bile to get into the gallbladder, well, it travels down from the liver and it travels up that cystic duct, and then when it travels out of the gallbladder, it's going to travel down that cystic duct in the other direction. Well, when it travels down the cystic duct in the other direction, it leads to the bile duct. And the bile duct, we've now highlighted that in purple and labeled it b. The bile duct connects the liver and the gallbladder to the small intestine. So again, bile is made in the liver. It travels out of the liver. If it's needed right then, it just continues down that bile duct and into the small intestine. If it's not needed, it sort of backs up into the cystic duct, gets stored by the gallbladder until it is needed. Now when it is needed, the gallbladder squeezes. Remember, it's this muscular sac, so it just the muscles contract. It squeezes to release that bile. All right. How does the gallbladder know to squeeze? There's a hormone for that. The gallbladder squeezing is going to be triggered by the hormone cholecystokinin or CCK, and this is a hormone that's released by the small intestine. So as chyme enters the small intestine, it'll send out signals saying like, Hey, this is what's here. This is what we need. One of those signals is cholecystokinin, which goes to the gallbladder and tells it to release the bile. Now cholecystokinin, that's kind of a complex word, but we can break it down and actually make sense. The root 'kinin', well, that refers to movement. You can think of words like kinetic. 'Chole' at the beginning here, well, that refers to bile. And 'cysto', we've already defined that. That refers to a bladder. So cholecystokinin, it tells the bile in the gallbladder to move. All right. So now that it's moved, it's moved down the ducts, it in the small intestine and mixing in the chyme. What does this bile do? All right. Well, the bile is going to be made of bile salts. Also, bile pigment, cholesterol, triglycerides, phospholipids, and electrolytes. But, really, we want to focus in on the bile salts and the bile pigment. Bile salts are going to be derived from cholesterol. So importantly, just like soap, these bile salts, the molecules have one end of the molecule that's hydrophilic. It mixes with water easily. And the other end of the molecule is going to be hydrophobic. It mixes with fats easily. This allows these bile salts to break up fats by emulsifying them. So just kind of like dish soap, well, it mixes with the fats and allows those fats to break up from being big globs. Right? So you can imagine if you eat oils or globs of butter, as they're in your stomach, they're in this liquid kind, they're sort of clumping together because those things don't mix well with water. You put in the bile, it breaks them up or emulsifies them, and you end up with these small droplets of fats. Now that's important because we need to use enzymes to break down the fat molecules themselves, and so we need as much surface area as we can. And those enzymes are dissolved in the chyme, so we need those fats to be broken up as much as possible, so these enzymes can access these fat molecules. So really importantly, the bile does not change the fat molecules chemically. It just breaks them up into smaller globs, so that enzymes can actually digest the molecules. All right. We're going to say here, well, the bile salts, they're released into the small intestine at the first section of the small intestine in the duodenum, but then they're going to be reabsorbed in the large intestine, and also some in that last section of the small intestine we're going to talk about called the ileum. So you put them in at the beginning of the small intestine, and you pick those bile salts back up after those fats are digested. They're then brought to the liver via the portal vein and recycled by the liver, so we just use them again. All right. The last thing that we need to know about bile, we're going to talk about this molecule called bilirubin. And bilirubin is the chief bile pigment, meaning it's one of the major things that gives bile its color. Bilirubin is going to be waste heme from the liver. One of the functions of the liver is to break down old red blood cells, and one of the byproducts you get, well, heme, remember, that's part of that molecule hemoglobin. So you have this waste heme that gets broken down into bilirubin, and it's put in the bile to get rid of and to get rid of take out of the body. Now this is interesting because this is what actually turns your feces brown. Bilirubin, when it breaks down, it turns a brown color, and it's actually the same reason that old bruises turn brown. In your bruise, the hemoglobin air breaks down, bilirubin is produced, and your bruise turns brown. In your digestive tract, that waste heme is put into the digestive tract. As it breaks down, it turns your feces brown. All right. So when you think of bile, you can think of what would happen to your feces if you didn't have bile. So if you don't produce bile, what actually happens? Well, those fats traveling through, they don't get broken up, and so these fats get traveled through in big globs, and people who don't produce enough bile, they have big globs of fat in their feces. Their feces is also a grayish color because there's no bilegulin. Now I don't know about you, but I think feces is kind of gross. But when I think about gray feces with big lumps of fat in it, that sounds even grosser. So be thankful for your bile. All right. That's what we got for this video. I'll see you down the road.

The Gallbladder Example 1

Our example tells us that gallbladder removal, or cholecystectomy, can be broken down. Cholar, remember, refers to bile. Systo refers to a bladder, here, the gallbladder. And ectomy, which is a surgery where you excise something or cut something out. So anyways, gallbladder removal is one of the most common surgical procedures, with over 1,000,000 surgeries performed in the United States each year. It seems like a lot. Indicate whether you would expect each of the following to increase, decrease, or show no change after gallbladder removal.

Taking out the gallbladder, do you expect there to be more or less total bile production? Well, the bile is produced by the liver. So, the gallbladder just stores it. So I actually think that there will be no real significant change. I have no reason to believe that there would.

Now, what about the amount of bile that can be released at one time? Well, the gallbladder is there to store bile, so you can get a big squirt of bile all at once. If you take it out, you can't get that big squirt of bile. So this, I think, is going to decrease.

It says, do you think that patients who have gallbladder removal are generally advised to avoid eating fats altogether, avoid eating foods with highly concentrated fats, or to not consider fat intake in their diet, and explain your answer. What do you think? Well, remember, bile is there to break up the fats in your food so that the enzymes can better access that fat as it's all mixed in with the chyme. Now if you take the gallbladder out, you still make bile. And remember, the liver is connected to the small intestine via the bile duct. So the liver is still making bile and that bile can still get into the small intestine. What you can't get is big squirts of bile, big releases of bile, sort of all at once from that gallbladder. So that suggests to me that you probably can still eat fats. Right? You're still getting the bile, but you don't want to eat a lot of fat at once because you can't get a lot of bile to break up those really fatty foods. So therefore, I am going to say avoid concentrated fats. And my reasoning is you can still make bile but can't release large amounts at once. Of course, if this were on a test, I would put that in some nice complete sentences.

With that, we're moving on to some practice problems. I'll see you there.

How would the gallbladder respond to an increase in cholecystokinin in the blood?

• A. Produce more bile.
• B. Remove bile salts from circulation.
• C. Relax to accommodate an influx of bile from the liver.
• D. Contract to release bile.

Which of the following statements about bile is true?

• A. Bile breaks down fats by breaking triglycerides down to fatty acids.
• B. Bile increases the surface area of fats in chyme, but it does not break them down chemically.
• C. The process of bile breaking down fats creates a byproduct that makes feces brown.
• D. Bile is synthesized by the gallbladder when stimulated by cholecystokinin (CCK).

Here’s what students ask on this topic:

What is the function of the gallbladder in the digestive system?

The gallbladder is a small, muscular sac located just below the liver. Its primary function is to store bile, which is produced by the liver. Bile plays a crucial role in the digestion of fats. When food containing fat enters the small intestine, the hormone cholecystokinin (CCK) is released, signaling the gallbladder to contract and release bile into the small intestine. Bile contains bile salts that emulsify fats, breaking them down into smaller droplets, which increases the surface area for digestive enzymes to act upon, facilitating fat digestion and absorption.

How does bile aid in the digestion of fats?

Bile aids in the digestion of fats through a process called emulsification. Bile contains bile salts, which have both hydrophilic (water-attracting) and hydrophobic (fat-attracting) ends. When bile is released into the small intestine, the bile salts surround fat globules and break them down into smaller droplets. This increases the surface area of the fats, making it easier for digestive enzymes, such as lipases, to break down the fat molecules into fatty acids and glycerol, which can then be absorbed by the intestinal lining.

What triggers the release of bile from the gallbladder?

The release of bile from the gallbladder is triggered by the hormone cholecystokinin (CCK). When partially digested food, or chyme, enters the small intestine, CCK is released by the intestinal cells. This hormone signals the gallbladder to contract and release stored bile into the small intestine. The bile then aids in the emulsification and digestion of fats present in the chyme.

What are the components of bile and their functions?

Bile is composed of bile salts, bile pigments (such as bilirubin), cholesterol, triglycerides, phospholipids, and electrolytes. Bile salts are crucial for emulsifying fats, breaking them into smaller droplets to aid in digestion. Bile pigments, particularly bilirubin, are waste products from the breakdown of hemoglobin and give bile its color. Cholesterol, triglycerides, and phospholipids are also present but play less direct roles in digestion. Electrolytes help maintain the pH balance in the digestive tract.

What happens if the body does not produce enough bile?

If the body does not produce enough bile, fats in the diet cannot be properly emulsified and digested. This leads to the presence of large fat globules in the feces, a condition known as steatorrhea. The feces may appear grayish and greasy due to the undigested fats. Additionally, the lack of bile pigments, such as bilirubin, results in the absence of the typical brown color of feces. This can lead to nutrient malabsorption and deficiencies, particularly of fat-soluble vitamins (A, D, E, and K).