4.1 process of fat absorption

1. emulsification of fats

when dietary fats enter the small intestine they are in large insoluble droplets which bile salts break into smaller micelles via emulsification

bile salts increase the surface area

for pancreatic enzymes, lipase, to work

2. lipase digestion

pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides which are absorbed

without bile salt induced emulsification

lipase would be unable to access the hydrophobic fat molecules effectively

3. micelle formation

bile salts surround the breakdown products (free fatty acids monoglycerides cholesterol and fat-soluble vitamins) forming micelles

these micelles act as transport vehicles

allowing the fats to be absorbed across the water based environment of the intestinal lumen

4. absorption into enterocytes

the micelles travel to the surface of the intestinal cells where the fat components are released and absorbed into the enterocytes, intestinal lining cells 

inside the enterocytes

fats are reassembled into triglycerides

5. chylomicron formation

the reassembled triglycerides + cholesterol + fat soluble vitamins are packaged into chylomicrons, lipoprotein particles that are too large to enter the blood stream directly

chylomicrons enter the lymphatic system

before eventually reaching the bloodstream

bile salts are essential for the absorption of lipophilic drugs (fat soluble)

many drugs with poor water solubility rely on bile salts for their absorption

the most important function of bile salts in drug absorption is their ability to for micelles

the hydrophobic core of the micelle allows fat soluble drugs to be shielded by the aqueous environment of the intestinal lumen facilitating their solubilisation → absorption

1. emulsifcation of liophilic drugs

when bile salts are secreted into the small intestine they surround lipophilic drug molecules breaking them into smaller more manageable particles

2. micelle encapsulation

bile salt hydrophobic outer shell faces the watery environment of the intestiines why the hydrophobic core encapsules the lipophilic drug allowing them to be transported

3. transport to the entercyte surface

micelles carry the lipophilic drug to the surface of the enterocytes, intestinal cells, where the drugs are released from the micelle and absorbed across the cell membrane

4. absorption of drugs into entercytes

once the drug is released from the micelle at the enterocyte surface it diffuses across the lipid membrane and is taken into the lymphatic system if blood stream