What is the main function of the gallbladder?

The main function of the gallbladder is to store and concentrate bile. Bile is produced by the liver and plays a crucial role in the digestion and absorption of fats in the small intestine. Once bile is synthesized in the liver, it is transported to the gallbladder, where it is stored until needed during digestion. When food enters the small intestine, particularly fatty foods, the gallbladder contracts and releases the concentrated bile into the duodenum to help emulsify fats, making them easier for digestive enzymes to break down.

This specific role of the gallbladder is essential for efficient digestion and shows how it contributes to the overall digestive process. The other options do not pertain to the gallbladder's primary function: digestion of fats is a broader process involving bile and enzymes, while insulin production is primarily the function of the pancreas, and blood filtration is carried out by the kidneys.