Class 11 Biology (India)
Explore the small intestine's role in digestion and nutrient absorption. Learn about the three parts: the duodenum, where most digestion occurs, the jejunum, where nutrients are absorbed, and the ileum, where important vitamins are absorbed. Discover the role of villi and microvilli in increasing surface area for digestion. Created by Raja Narayan.
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- Is there any difference between the digestive system and the GI tract?(15 votes)
- Yes! The GI tract is only made up of the stomach and intestines through which food travels. The digestive system also includes organs that help with digestion, like the pancreas and liver.(26 votes)
- I'm not good at stereometry and even at plane geometry. Could you explain to me how lots of villi (alveoli etc) can increase area in confined space?(6 votes)
- Take a piece of paper. Fold it so it looks like this:
The paper has the same surface area as before, but if you put it on the table and measure the space it occupies, the folded paper occupies less area than the unfolded paper.(19 votes)
- Why is the "small intestine" really a large intestine and the "large intestine" really a small intenstine I don't get some one help me!(7 votes)
- How is the duodenum protected from HCl that comes from the stomach?(3 votes)
- When the duodenum receives the chyme from the stomach, it signals the pancreas to release bicarbonate and digestive enzymes such as trypsin, lipase and amylase into the duodenum. These enzymes along with breaking down the food particles also neutralize the hydrochloric acid coming from the stomach.(7 votes)
- At2:18, Rishi mentions that there's stomach acid present in the duodenum. What happens to this stomach acid, and how does it not end up digesting the walls of the small intestine? Are there cells in the walls of the small intestine secreting bicarbonate to neutralise the acid, like there is in the stomach?(3 votes)
- Okay! so you are half way right. Yes, there the food existing through the pyloric spinchter is acidic, and there is also some acidic that makes its way through the duodeum. But as you said and we know that the pH in the small intestine is slightly alkaline, and the pH is maintained because of the bicarbonate acting as a buffer that have a range it operates with and that is usually in normal conditions. Sometimes in cases like duodenum ulcers that is usually the result of the excessive release of HCl from the stomach can damage the wall of the duodeum because it doesn't have that mucus protective layer in the stomach, also the buffer wouldn't be working because the amount of acid exceeds the buffer working zone that is usually pH+_ 1.(6 votes)
- Why does the Ileum absorb the important components (such as vitamin K, etc). In the introduction to the Gastrointestinal video, it said that the large intestine absorbs those components. Please help ASAP. I have a test coming up on the alimentary canal.(3 votes)
- the absorption of the vitamins depend of certain conditions and molecules like in case of vit B12 . it needs Internsic Factor (IF ) which released form stomach and travel to the illeum
cobalamins attach to intrinsic factor. Intrinsic factor then carries the cobalamins to the last section of the small intestine, the ileum.
The cells lining the ileum contain receptors for the cobalamin-IF complex. The cobalamin-IF complex protects the cobalamin against bacterial and digestive enzyme degradation . The IF-receptor also ensures that cobalamins will be given priority for absorption over non-cobalamin corrinoids.
i hope it would help :)(2 votes)
- What is the need of the alimentary organs in the digestive system?(2 votes)
- Without these alimentary organs, macronutrient polymers would be too long and bulky to absorb into the bloodstream. The sole aim of the digestive system is to take food and extract all the nutrients (such as triglycerides, carbohydrates and proteins) from it into the blood. This can only be done by breaking it down until it is small enough for absorption to occur.
Hope this helped!(3 votes)
- what is the muscle tissue in villi for?(1 vote)
- In general, there is muscle in the small intestine to regulate muscle contractions. These contractions help move chyme along the digestive tract and also help regulate more absorption. There are two types of contractions:
1) Peristalisis: these rythmic contractions help squeeze the food through the small intestine. Peristalisis only moves food in one direction which is down the digestive tract. We see peristalisis throughout the whole digestive system.
2)Segmentation: this is when the muscular walls undergo localized contractions and relaxations that serve to mix the intestinal contents with the secretions (eg. pancreatic juice) and further increase the surface area of substrate available for enzymatic hydrolysis. Therefore, this allows to food to be digested even further and more stuff to be absorbed. Segementation can push the chyme back and forth in both directions as well.(5 votes)
- But what exactly is the role of the brush border enzyme in the digestion?what exactly does is help to digest?(for e.g. fats, proteins ,carbs,etc.)(3 votes)
- You will find that information in this video ( it will answer your question) : https://www.khanacademy.org/science/health-and-medicine/human-anatomy-and-physiology/Gastrointestinal-system-introduction/v/small-intestine-part-2-digestion(1 vote)
Voiceover: Did you know that the stomach flu can make you temporarily lactose intolerant? It's true. So, in this video, we will talk about how that happens. And in detail, how the small intestine works. So, as a review, once you put food into your oral cavity or your mouth, it's chewed up and then sent down the esophagus where it ends up in the stomach where it's churned and then introduced to acid where it gets broken down into chyme and then delivered into the first part of your small intestine. Now, the small intestine has three different parts to it. So, let's take a better look. So, the first part of the small intestine is called the duodenum, the duo-denum. This receives the chyme that just got processed in the stomach and it's the part of the entire GI tract where the most digestion occurs. The most breakdown of food products will happen in the duodenum. All right, so the next part of the small intestine is called the jejunum. I'll just write that right here, the jejunum. And this is the part of the entire GI tract where the most absorption occurs, anywhere. So, the most absorption of nutrients is going to happen in your jejunum, the jejunum. Then, finally after your food passes to the jejunum, it gets to the last part of the small intestine and that's called the ileum, the ileum (I-L-E-U-M). And the ileum, now this doesn't have a superlative like the most digestion or the most absorption, but there are some pretty important things that are absorbed here. Things like vitamin B12, vitamin A, D, E, K. So, there are some important things that are absorbed here. So, I'm just going to write important absorption. There are some important things that are absorbed in your ileum. Now, the busiest part of your small intestine is the duodenum, because there are a bunch of things that are involved in this digestion process. So, there are four key things to keep in mind. First of all, your stomach is going to be delivering a bunch of chyme or processed food into the duodenum. So, you're going to be working with all this chyme here. In addition, you're going to have some stomach acid that process food into chyme. That's going to be present in the duodenum. In addition to the stomach, the liver and the gallbladder are also going to be important to deliver bile to your duodenum. So, they give bile. And as I'll talk about in a subsequent video, bile is composed of two different things. Bile salts and bile pigments. And beyond the liver and the gallbladder, the pancreas also delivers a couple of very important enzymes for digestion here. So, I'm just going to write enzymes for now. And in a minute, I'm going to go through and talk about which enzymes are delivered by the pancreas. And then finally the duodenum itself has what are called brush border enzymes, brush border enzymes. That are very important for activation of certain enzymes and also for digestion of several nutrients that we're going to discuss. So, let's talk a little more about this brush border. Now, if I would have make a little drawing of the duodenum right here. Remember that first part of our small intestine. I would draw just a little tube, connected right there. And then blow up the wall if I want to take a better look at what's going on right there. We would find then that there is a whole bunch of things than just meets the eye. First of all, the wall isn't just a straight line. There is actually a bunch of infoldings that are present on the wall to help increase surface area. Think about it. If we're trying to digest as much as we can here, we need to make sure that there are a lot of projections or a lot of space where we can make contact with the food that's passing by. So, if this is the inside of our duodenum, and this is the outside, just like how we drew up here. That's in and that's out. You can notice that this wall here has a whole bunch of projections on it. These projections are called villi (V-I-L-L-I), villi. And a single one of them is just called a villus, just a single villus. And these are just a couple of folds or these outpouchings that help increase the surface area of our duodenum. Now, that's not where the story ends. If we take a closer look at one of these villi, then we'd find that there are even more projections sitting on that, even smaller microscopic projections. So, for this single villus that had a horizontal line right here for its shape. Fair to draw it out here. You'd notice that it's not a straight line, but instead these also have a bunch of projections that are present on them. And if you were to guess why all these projections are in there? I'm sure you'd say to further increase our surface area. That's sort of the name of the game when we're in the small intestine. To increase our surface area. And so these little guys cutely enough are called microvilli, microvilli. And a single one is just called a microvillus. So, we've got these villi right here or the single villus that you can see if you just blow up the wall of the duodenum. And then if you blow up a single villus, you'll find that they have a whole bunch of microvilli that are found on them too, to increase our surface area because that allows for better digestion. And when we say brush border enzymes, these are a whole bunch of enzymes that are present on this brush border. You guys think about it. These villi and these microvilli, they're no different from bristles on a comb. They act to increase surface area or places where you're going to have interaction with food that you want to digest. And so there are enzymes that are present on this brush border. So, just to make the point, all of these microvilli and villi together, that's what makes up the brush border of our duodenum. The brush border, which is the increased surface area of the wall helps to digest food with our brush border enzymes that are present. And as we'll see later, in the jejunum, it helps for absorption. So, now let's talk about the digestion process in detail.