According to the Encyclopedia Britannica, the gallbladder is a small, membranous, muscular sac used to store and concentrate bile. Bile is a fluid the gallbladder receives from the liver that aids in digestion in the small intestine.
Found underneath the liver, the gallbladder is pear-shaped and can hold about 1.7 fluid ounces, or 50 mL maximum. Its inner wall is lined with a mucous-membrane tissue akin to that found in the small intestine; this tissue contains hundreds of microvilli, which are microscopic projections that boost the area of fluid absorption. The cells contained in these tissues allow bile to absorb inorganic salts and water, resulting in bile being between 5 and 18 times more concentrated than it was when it was originally made in the liver.
When the gallbladder’s muscle wall contracts, bile is discharged through the bile duct and into the small intestine’s duodenum. The bile duct is made up of three branches shaped like a “Y”: its lower segment is called the common bile duct, and it culminates in the small intestine’s duodenal wall. Bile flow into the duodenum is regulated by the sphincter of Oddi, which is found at the end of the common duct. The bile duct’s upper right branch is called the hepatic duct; it leads to the liver, where bile is made. Finally, the upper left branch is known as the cystic duct, and it leads to the gallbladder, where bile is kept.
Bile moves from the liver’s two lobes into the common and hepatic bile ducts. If there’s food in the small intestine, bile will continue on, moving directly into the duodenum. However, if the small intestine is empty, the sphincter of Oddi will remain closed, and bile moving down the common duct will pool and be forced backwards until it reaches the cystic duct, which is open. Then, bile will flow back into the gallbladder, where it will be stored–and concentrated–until it’s needed. And when food finally enters the duodenum, the sphincter in the common duct will open, the gallbladder will contract, and bile will enter the duodenum once more to help in fat digestion.
There are a number of disorders that can develop within the gallbladder, such as gallstones. The Ezra abdominal, torso, and full-body MRIs may screen your gallbladders for various cancerous and precancerous conditions; you can learn about our screening plans here.