Content Reviewers:Rishi Desai, MD, MPH
The gallbladder is a muscular pear-shaped storage sac attached to the lower surface of the liver.
In addition to being able to store about 50 mL of bile, it also concentrates the bile before secreting it into the duodenum after meals.
Bile is produced by the liver and secreted into a network of intrahepatic bile ducts before reaching the common hepatic duct.
The common hepatic duct then connects with the cystic duct, which allows the bile to flow into the gallbladder.
When the gallbladder contracts, bile is pushed back out of the gallbladder through the cystic duct and flows into the common bile duct, which joins with the main pancreatic duct before emptying into the duodenum.
Focusing on the gallbladder, at low magnification the gallbladder wall has three main layers: the inner mucosa, tunica muscularis, and its outer layer of connective tissue called the external adventitia or serosa.
If we first take a closer look at the mucosa, we can see that the mucosa has many mucosal folds or rugae, but they’re not long enough to be considered villi.
Some of the folds of the mucosa are deep enough to form the appearance of cross-bridges when seen under a microscope, such as the two in this image.
If we increase the magnification to 40x, we can see that the mucosal epithelium is lined with simple columnar cells that are overlying the lamina propria, which contains dense irregular connective tissue, many immune cells, and small capillaries.
In the bottom left of this image, we can see a portion of the next layer underneath the mucosa, called the tunica muscularis.
Here we can see more of the tunica muscularis or the muscular layer of the gallbladder.
The muscles in this layer are grouped in bundles of smooth muscle, but they are actually randomly oriented.
The contraction of these muscles results in the emptying of the gallbladder.