Besides the liver which is the other adnexal gland of the digestive system that releases substances in the duodenum participating in extracellular digestion?

The other adnexal gland of the digestive system is the pancreas. This organ makes digestive enzymes that digest proteins (proteases), lipids (lipases) and carbohydrates (pancreatic amylases). Other digestive enzymes, like elastase, gelatinase, ribonucleases, carboxipeptidase, and deoxyribonuclease are also secreted by the pancreas.

Digestion System - Image Diversity: pancreas