The Gallbladder and Gallstones

Anatomy and Physiology Q&A

What is the gallbladder?
The gallbladder is a pear shaped organ located on the liver that stores bile. It is connected to the intestinal system by the cystic duct which in turn empties into the common bile duct. When we eat a large or fatty meal, nerve and chemical signals cause our gallbladder to contract thereby adding bile into our digestive system.

What is bile?
Bile is a complex fluid composed of bile salts, cholesterol and other molecules (phospholipids and lecithin). The bile salts are the breakdown products of hemoglobin, the oxygen carrying pigment of red blood cells. Bile salts and bile itself are formed in the liver and excreted into bile ducts which converge in the liver to form the main bile ducts. Just as there is a left and right liver lobe, there is a left and a right hepatic (liver) bile duct which join to form a single bile duct, the common hepatic or common bile duct.

The common bile duct enters the duodenum, the earliest part of the small intestine where digestion and absorption of food begins. You may recognize the word duodenum since it is the most common site for ulcers. Normally we make 1000 to 1500cc of bile a day. It is constantly produced. As a result, there is always a steady amount of bile entering our intestinal tract. Some of it goes into the gallbladder as it comes down the duct. It is stored there until neurochemical signals cause the gallbladder to contract. This provides additional bile to the intestinal system. These neurochemical signals usually occur after eating.

Is bile necessary?
Yes. We absolutely need bile to absorb fats. Our intestinal lining can absorb water but not fats. Since fat is not dissolvable in water (like oil in water) we can not absorb fats unless something makes the water and fats attach. This is the function of bile; it can bind to both water and fat. Therefore, when we absorb water, the fats absorb with it if bile is present to link the water to the fat. If we do not have any bile we will not be able to absorb fats. This will in turn lead to severe deficiencies of essential fats, alter our metabolism, cause significant problems which will impair living and lead to diarrhea.

Is the gallbladder necessary?
No. The gallbladder seems to be a vestigial organ. That is, the gallbladder is an organ which was important at some point in our evolution but no longer necessary. Indeed, gallbladders have been removed from people for over one hundred years without any known side effects. The amount of bile that is constantly coming into the intestinal system via the common bile duct is more than adequate, under normal circumstances, for absorption of the fats in our diet. However if one eats a particularly rich and or fatty meal, some degree of diarrhea may result.

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