What is a micelle?

Micelles allow non-soluble lipid products to mix with chyme and travel through the small intestines.

OVERLY SIMPLIFIED EXPLANATION OF HOW LIPIDS GET INTO THE BLOODSTREAM

Lipids are hydrophobic, meaning they can't dissolve in water. Blood is watery, and so is chyme (semi-digested food). If you put raw lipids into those solutions, they'll separate like oil and water in a bottle of Italian dressing and cause all kinds of problems. Instead, you have to package them up with some hydrophilic stuff, so that they'll "flow" along with the rest of the blood/chyme/lymph/whatever, and reach their destination.

The package that allows lipids to mix into chyme is called a MICELLE. The package that allows lipids to mix into the bloodstream is called a CHYLOMICRON.

Micelles are made up of lipid components (cholesterol, fatty acids, etc. -- the stuff you get after the fat is emulsified by bile and broken down by lipases) and bile salts. Micelles are formed in the duodenum and travel to the jejunum, where they are taken up by epithelial cells in the intestinal villi and disassembled.

The lipid bits are then mixed with proteins to form a chylomicron. This allows the lipid to be carried by the bloodstream. HOWEVER! Chylomicrons are huge -- way too big to enter the bloodstream through a capillary. So they have to take the scenic route through the lymphatic system. Special lymph vessels called LACTEALS inside the villi take up chylomicrons and circulate them through the lymphatics, where they eventually reach the bloodstream via the left subclavian vein.