Digestion

This week, we've been able to learn a little bit more about digestion. The goal of digestion is to break down nutrients we eat so that our body can later absorb them along with other vitamins and minerals. There are two types of digestion: Mechanical Digestion and Chemical Digestion. Mechanical digestion are the process in digestion in which there are more muscle contraction involved, such as using our teeth to chew down food or using the esophagus to push down the food to the stomach. Chemical digestion on the other hand includes those processes in digestion that more enzymes and chemical reactions occur. For example, the absorption of nutrients in our small intestine can be classified as a part of chemical digestion. Another thing learned was the process in which digestion occurs. Let´s suppose I just had a sandwich and a coke for lunch. Digestion starts in the mouth when I'm chewing my food with my teeth. The salivary glands in my mouth produce saliva, a substance containing water and salivary amylase. The salivary amylase is an enzyme that will help break down sugars such as glucose and maltose that are present in my food. With the sandwich example, the bread will start to desintegrate if i just leave it in my mouth, thanks to the salivary amylase. After the mouth has broken down the most of the food into smaller pieces, the food now travels to the stomach by the esophagus. The esophagus is a tube that connects our mouth with our stomach. Its job is to push down the food until it can reach the stomach. The stomach contains gastric juices, which make the stomach very acid. These juices, or hydrochloric acid, help break down the food, kill contagious microorganisms, and create enough pH to activate pepsin. Pepsin is an enzyme which is most active in acid or higher pH. The stomach is the organ containing the highest pH in our body. What the pepsin does is it breaks down proteins into amino acids. The stomach also contains mucus on its wall to prevent it from irritating. The mucus then protects the stomach from its own acids. When the food leaves the stomach, it can hardly be called "food" any more. From now on, the food has been broken down into small nutrients. After the stomach, the nutrients now travel to the small intestine or duodenum. The role of the small intestine is to absorb all the nutrients, vitamins, and minerals possible. The reason why the small intestine can absorb so many things at a pretty fast rate is because of the villi. The villi can be found on the intestine wall and they look like tiny, finger-like projections. Villi or villus create more surface area because of their "squiggly" structure. This way, even more nutrients can be absorbed. They also have a very thin membrane, which facilitates the passage of nutrients from the intestine out. The cells from that membrane have villi as well, but they are called microvilli, since they are very small structures. They increase the surface area even more. In addition, the villus are close to blood vessels, which means the nutrients can go directly to the bloodstream. And lastly, the villus also contains a capillary bed, which give the bloodstream more volume. The villus absorbs things such as fatty acids, amino acids, and glucose. The nutrients in the small intestine are mixed with three different liquids: bile, pancreatic juice, and intestinal enzymes. The bile's main role is to mix with the fats to kind of make them smaller to allow absorption. Bile is produced in the liver and stored in the gallbladder. The bile in the gallbladder is more concentrated. The pancreatic juice is produced in the pancreas and it neutralizes the the acidic nutrients that just came from the stomach in order for enzymes to work on them properly. The intestinal enzymes include maltase, lacteal, surcease (which are enzymes that break down sugar), and tripsin (breaks down protein). After most nutrients have been absorbed in the small intestine, the leftovers go to the large intestine. Large intestine's main goal is the absorption of water. It also absorbs some leftover nutrients, but mainly water. After the large intestine is done absorbing what's left, all the waste goes to the rectum, which is the last part of the large intestine. Finally, when we go to the bathroom, we excrete all the waste through the anus and digestion is terminated.

“How do I evaluate my performance in Bio I and what are my goals for this year?”

In my sophmore year of high school, I decided to take the IB BIOI class. The grade I earned at the end of the year was a B-. Some people said my grade was not that bad. In my opinion, I could've done better, and that is exactly what I plan to do in the IB BIO II class on my junior year. My goal in my IB BIO II class is to pass the class with better grades than last year. Part of the reason why I got that grade last year was probaly because I didn't revise my labs before turning them in. The problem with this was that most of them had errors I had forgoten to fix or that I hadn't noticed them because I did not check my lab before turning it in. This year, I plan to double check all of my labs in order to ensure they do not have any type of errors. Also, when it came to a test, I would study for it, but not as much as I should. Then, on the day of the test, I wouldn't get the grade I wanted to. Again, I will correct this on my junior year by dedicating as much time as I need to prepare for my test. By doing all of the above, I will achieve my goal for the class this year and get better grades than last year.