Which part of the GI tract contributes little to fat digestion?

The mouth contributes minimally to fat digestion primarily because the digestive process in this area focuses on the mechanical breakdown of food and the initial enzymatic digestion of carbohydrates and proteins through saliva. While the mouth does play a role in lipid digestion by mixing fats with saliva and initiating some chemical breakdown, the actual enzymatic breakdown of fats is limited since there are very few digestive enzymes in saliva that specifically target fats.

The primary site for fat digestion is the small intestine, where bile salts from the liver and pancreatic lipase from the pancreas play crucial roles in emulsifying fats and breaking them down into fatty acids and glycerol. The stomach also produces some gastric lipase, but the majority of fat digestion occurs in the small intestine after the food has been mixed with bile and pancreatic enzymes. Thus, compared to these other organs, the mouth has a minimal contribution to fat digestion, making it the correct choice for this question.