Digestion of fats:

Butter is a fat product and gets digested in the small intestine. The bile juice secreted by the liver contains bile salts that break down large fat globules into smaller globules, so as to increase their surface area for the action of lipase. This process is referred to as emulsification of fats.

After this, the pancreatic lipase present in the pancreatic juice and the intestinal lipase present in the intestinal juice hydrolyse the fat molecules into triglycerides, diglycerides, monoglycerides, and ultimately into glycerol.

$\mathrm{Fats}\underset{\mathrm{lipase}}{\overset{\mathrm{Pancreatic}}{\to }}\mathrm{Triglycerides}+\mathrm{Diglycerides}$

$\mathrm{Diglycerides} \mathrm{and} \mathrm{monoglycerides}\stackrel{\mathrm{Lipases}}{\to }\mathrm{Fatty} \mathrm{acids}+\mathrm{Glycerol}$

Absorption of fats:

Fat absorption is an active process. During fat digestion, fats are hydrolysed into fatty acids and glycerol. However, since these are water insoluble, they cannot be directly absorbed by the blood. Hence, they are first incorporated into small droplets called micelles and then transported into the villi of the intestinal mucosa.

They are then reformed into small microscopic particles called chylomicrons, which are small, protein-coated fat globules. These chylomicrons are transported to the lymph vessels in the villi. From the lymph vessels, the absorbed food is finally released into the blood stream and from the blood stream, to each and every cell of the body.