Your small intestine has two important responsibilities. First, it finishes digesting your meal, further breaking down its proteins, fats, and starches into simpler compounds. To perform this task, it gets help from several accessory organs, including your pancreas, liver, and gallbladder. Second, your small intestine absorbs your meal’s final, fully digested nutrients, pulling them out of the pasty digestive solution and passing them directly into your bloodstream, making them available to the rest of your body. The easiest way to understand what’s going on in your small intestine is to consider the different types of food it processes:
• Carbohydrates. Several hours ago, you began to digest your breakfast toast in the relatively easygoing environment of your mouth. Now, deep in your abdomen, the process continues with a new series of more powerful enzymes that shatter the remnants of your toast into simple sugars. Your body secretes these enzymes from your pancreas—a plain looking slab of an organ that squirts digestive juices into your small intestine.
• Proteins. More recently, your stomach started working on the proteins in your eggs and sausage. Your small intestine finishes the job, again with the help of enzymes from your pancreas. The end results are amino acids—fundamental building blocks your body uses to assemble hundreds of thousands of different biological compounds.
• Fats. Your body has to break these down into fatty acids. Once again, the pancreas secretes the enzymes your small intestine needs to do the job. However, before these enzymes can get to work, your body needs a way to break the big, greasy globules of fat into tiny droplets, in much the same way that dish detergent dissolves the oil from last night’s deep-fried chicken. Two organs solve the problem. First, the liver—a multifaceted organ whose main responsibility is filtering blood—creates bile that does the trick. Second, the gallbladder—a kiwi-sized organ that looks like an unremarkable green pouch—stores and concentrates this bile between meals.
Once your body breaks down these nutrients, they seep through your thin intestinal walls, along with various vitamins and minerals. To make this process easier, thin folds lined with tiny hairs cover your small intestine. These details help increase your small intestine’s surface area to promote nutrient absorption.
With the pancreas’s high-powered digestive abilities, you might wonder why it doesn’t eat itself. The trick is that the pancreas releases harmless, inactive enzymes. These enzymes switch themselves on when they meet up with the strong acids in the partly digested food in your intestine.
Source of Information : Oreilly - Your Body Missing Manual