What happens to bile salts during the lipid absorption process after micelles diffuse into the cell membrane?

During the lipid absorption process, bile salts play a critical role in emulsifying dietary fats, which allows for the formation of micelles. Once the micelles diffuse into the cell membrane of enterocytes (intestinal cells), bile salts are not destroyed or converted into cholesterol. Instead, they are primarily reabsorbed in the ileum, the final section of the small intestine.

This reabsorption is crucial because it allows the body to recycle bile salts and utilize them again in the digestion of fats, promoting efficient lipid absorption. Approximately 95% of bile salts are reabsorbed in the ileum and returned to the liver through the portal circulation, where they can be reused. This recycling mechanism maximizes the efficiency of digestion and ensures a steady availability of bile salts for future fat emulsification and absorption.

The excretion of bile salts in feces occurs only for the small percentage that is not reabsorbed, which underscores the importance of their reabsorption in maintaining the digestive process.