GALLBLADDER, DRAWING. GALLBLADDER, DRAWING The gallbladder is a small sac lying under the liver. The gallbladder collects bile salts secreted by the liver. Bile salts play an important role in digestion. After a meal, the gallbladder contracts when the food bolus enters the duodenum, releasing bile salts into the digestive tract. Bile salts are particularly important for fat digestion and absorption.