 Can you believe your digestive system is as long as a bus? Yep, it's about nine meters long all wrapped up inside your body a Lot of things go on in your digestive system, not just digestion. What else do you think happens? Digestion goes hand-in-hand with absorption which happens in your small intestine, which is what we're going to look at in this video Digestion is the breakdown of food from large insoluble molecules into small molecules, which can be used by your body Digestion involves many organs before it reaches the small intestine For more information on the roles of these organs in the digestive system watch this video Enzymes and other chemicals such as bile break down food For more on the role of enzymes and bile in digestion watch these videos As they move through the digestive system carbohydrates are broken down into sugars Proteins are broken down into amino acids and Fats are broken down into fatty acids and glycerol But the job of the digestive system doesn't stop at digestion For our body to make use of these small soluble molecules. We need to absorb them into our bloodstream This happens in the small intestine The small intestine is made up of lots of tiny finger-like projections called villi The villi increase the surface area of the small intestine The larger the surface area the more absorption that can take place Each villus has a tiny blood vessel called a capillary and another vessel called a lactil The food molecules pass from the villi of the small intestine into either the blood capillary or the lactil Once absorbed into the blood vessel in the small intestine the digestive food molecules can then be transported around the body To where they are needed So why did those large molecules need to be broken down in the first place? The small intestine is kind of like a sieve it has small holes in it Small molecules are able to pass through those holes whilst large molecules cannot So carbohydrates proteins and fats are all too large to pass through the holes in the small intestine But sugars amino acids fatty acids and glycerol are all small enough to pass through Sugars and amino acids pass through the holes into the blood capillary While fatty acids and glycerol pass into the lactil of the villi These small molecules move by diffusion moving from a high to a low concentration For example the small intestine has a high concentration of sugar molecules Whereas the blood supplying the small intestine has a low concentration of sugar So the sugar moves down its concentration gradient from a high concentration in the small intestine Through the holes in the villi into the blood capillary where it's in low concentration Sugar amino acids fatty acids and glycerol all use diffusion to move into the blood within the small intestine So after digestion breaks down large molecules into small molecules Absorption of the small molecules happens inside our small intestine by diffusion into the blood vessels What an amazing system if you like the video give it a thumbs up and don't forget to subscribe Comment below if you have any questions. Why not check out our Fuse school app as well until next time