[Music] oh what is that it's enough to put me off my food but that's where your food goes the digestive system all right it's in there so what exactly is digestion digestion is the process by which food gets broken down into small molecules so that it can be absorbed by the body ah it must be time for a break and a snack you're not supposed to eat them these are the seven nutrient groups how many can you recognize um that's carbohydrates that's protein fat that's vitamins and minerals well that's five but where are the other two that's water and last but not least ruffage oh yeah I always forget about those we all need a certain amount of each of these to give us a balanced diet so no more chocolate bars for you now the food we eat has to be broken up before our bodies can use it by our teeth sort of but the real work comes from the stars of the show enzymes so what are enzymes then they're protein molecules which act as biological catalysts oh catalysts I remember this from chemistry they speed up chemical reactions that's right most chemical reactions in living organisms would happen too slowly without enzymes that's why we have enzymes in every cell in our body but we're going to limit ourselves to digestion here oh good now digestive enzymes help to break down large food molecules but only three of these food groups have large molecules carbohydrates proteins and fats so there's one special enzyme which breaks down these three food groups it's not quite that simple each group has its own special enzyme for instance carbohydrates broken down by an enzyme called amalay so is that what's happening there then those particles the amalay enzyme breaking down carbohydrate yes and if we look even closer we can see that the enzyme molecule fits exactly into a carbohydrate molecule just like a key in a lock oh yeah so the carbohydrate molecule breaks down into smaller bits that's right it's converted into simple sugars like glucose so that it can be used by the body easily fine I got it so amales breaks down carbohydrate so if I were to eat a slize of bread it would really get the amalay enzyme going but what about the enzymes that break down proteins and fats proteins are broken down by an enzyme called proteas These are broken into smaller molecules called amino acids whilst fats are broken down by an enzyme called lipase and these are broken down into fatty acids and glycerol right we know which enzyme does the job and what job it does but where do these enzymes come from in the first place we can see here that all three of these are produced in the pancreas there and the small intestine there but amas is also produced in the salivate glands and protease is also produced in the stomach you've got it so what happens now well now that the food molecules are much smaller they can be absorbed by the blood where does all this activity take place in the small intestine where all our digestive enzymes are present in fact your small intestine is an amazing structure how so well it's got muscular tissue all along its length what we've got muscles in our intestine well the food has to move along somehow this squeezing action that pushes it along is called Paralis clever and that's not all the inside of the small intestine is covered with millions and millions of finger-like things called Philly oh look just like my mom's washing up gloves I'm surprised to even know what a pair look like cheeky so these things the villy is what helps us absorb our food you've got it they've got a huge surface area a very thin layer of cells and a very good blood supply which all allow for quick absorption of food hey that sounds just like the alvioli in the lungs yep same principles and after absorption the blood carries the food to all the cells in the body groovy I think we need to see the whole process from start to finish though wo a great big burger getting sha so the amales enzyme is starting to work already uh-huh and then it's swallowed so it passes down the esophagus into the stomach where it's paneled by the stomach's muscular walls and the proteas enzyme gets to work converting proteins or in this case the meat of the burger into amino acids so then passes into the small intestine with all its fold and villy and more enzymes and more enzymes before being absorbed into the blood anything that's left moves along to the large intestine where excess water is absorbed from the food then what's left left moves down to the rectum where feces is stored ready for expulsion oh now that's really put me off my food