When you eat some real fatty foods, like say some delicious french fries, they make their way to through the stomach and into the small intestine. At this point they aren’t really french fries anymore, but since they’re high in fat, they’re still a little more difficult to absorb, and that’s where your gallbladder comes in.
This high fat food stimulates the gallbladder to squeeze out some bile into the small intestine, that bile emulsifies the fat, or basically mixes the fat up, and makes it easier to absorb.
This is pretty much your gallbladder’s job—store and concentrate bile until the time comes to send it to the small intestine. It’s not the most glamorous of jobs, but hey, gotta start somewhere.
If we take a closer look at this magical substance, we’d get a rough breakdown that’s something like the following: ~70% bile salts and acids, ~10% cholesterol ~5% phospholipids, ~5% proteins, and 1% conjugated bilirubin, and the rest, small amounts of various other compounds like water, electrolytes, and bicarbonate.
Bile salts and acids are mostly a product of cholesterol metabolism, so an acid might look something like this and its salt is the anionic form, something like this (ROO-) group.
These acids and their salts have both hydrophobic and hydrophilic sides, making them amphiphilic, which help them make cholesterol and fat in the gut more soluble in bile.
The phospholipids are mostly lecithin, also amphiphilic, and also help make cholesterol and fats more soluble in bile.
Gall-stones are these round and solid stones you can find inside your gallbladder, and they’re made from the components of bile, and so they’re categorized depending on what they’re made of, the most common ones are cholesterol stones, but there’s also bilirubin stones, which are sometimes called pigmented stones.
The first type, as you might guess, are made mostly of cholesterol that has precipitated out of the bile as a solid and formed these solid stones. These account for around 75 to 90% of cases.
This cholesterol precipitation can happen in a couple ways, first, the bile can become supersaturated with cholesterol, meaning that the bile has so much cholesterol that the bile salts and acids or phospholipids can’t hold any more in solution, because remember that these all help make the cholesterol more soluble in bile, and so the cholesterol comes out of solution as a solid.