Wikipedia says :

The contents of these micelles (but not the bile salts) enter the enterocytes (epithelial cells lining the small intestine) .....

So, where do the bile salts go? Additionally, what prevents them from being absorbed by the plasma membrane?


1 Answer 1


The fatty acids within micelles are taken up by enterocytes in the upper/middle part of the small intestine (duodenum/jejunum) through selective transporters in their plasma membrane, which do not accept bile acids. The SLC27A4 protein is thought to be the principal transporter for fatty acids in enterocytes, although there has been some controversy about this.

As a result of this selective uptake of fatty acids in this part of the intestine, the bile acids are left behind in the micelles, as they are emptied of fatty acids. They travel down the small intestine until they reach the ileum, where enterocytes express a bile acid transporter, SLC10A2, which performs active uptake of the bile acids. The bile acids are then secreted on the opposite (basolateral) side of these enterocytes; enter the portal vein; and travel back to the liver, where they are reused. This is known as the enterohepatic circulation. A review of these mechanisms is found here.

So the uptake of fatty acids and bile acids differs by location in the intestine. First the emulsified fatty acids are extracted, then the bile acids are recovered in the ileum. There is also some passive transport (diffusion) of bile acids into enterocytes throughout the intestine, but this is considered a minor mechanism.


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