The gallbladder is a small green intraperitoneal sac that lies in the fossa between the left and right hepatic lobes at the level of the ninth rib and is directly connected to the liver via its fibrous capsule. Its function as an accessory organ to the foregut is to store and concentrate bile that is created in the liver and to systematically release it into the bile duct which connects to the duodenum so that digestion and fat absorption can take place. This article will highlight the anatomical parts of the gallbladder, its adjacent ductal system and its vascular, lymphatic and nervous supply.
Parts of the Gallbladder
There are three main parts to the gallbladder. The fundus of the gallbladder can be found at the level of the ninth costal cartilage and can be seen to slightly protrude from under the inferior aspect of the liver, just superior to the transverse colon. The body of the gallbladder lies under the cover of the liver anteriorly, but is also in contact with the transverse colon inferiorly and the duodenum posteriorly.
Lastly, the neck of the gallbladder is bent into an s-shape so it is able to join the cystic duct. The cystic duct is opened and closed via the spiral valve which is made by the mucosa that surrounds it in a spiral formation.
The Bile Duct
The common bile duct is formed via the merger of the cystic duct and the common hepatic duct. It merges with the main pancreatic duct to form the hepatopancreatic ampulla which enters the second part of the duodenum via the major duodenal papilla. It is here that the contents of the gallbladder and the pancreas meet the digested stomach contents for further processing on a molecular level.
Innervation, Blood Supply and Lymphatic Drainage
Blood is brought to the gallbladder via the cystic artery which stems from the right hepatic artery. It is collected by the cystic veins of which some drain the neck and biliary ducts and empty into the portal vein while others drain the body and the fundus and after empty back into the liver.
The hepatic nodes are responsible for the lymphatic drainage of the region. Innervation of the gallbladder consists of sympathetic fibers from the celiac plexus, parasympathetic fibers from the vagus nerve (CN X) and sensory fibers from the right phrenic nerve.
The presence of gallstones, which is clinically known as cholelithiasis is best described as hard spherical deposits of excess byproducts that are needed for the formation of bile, that form within the gallbladder. The two main types of stone are those made of cholesterol and those called pigment stones. The latter form due to chronic hemolysis, a biliary infection or a gastrointestinal disease such as Crohn’s.
Cholesterol stones however have a much longer list of causative factors such as old age, excessive female sex hormones, obesity and insulin resistance, gallbladder stasis and dyslipidemia syndromes to name but a few. Surgery is usually advised in order to avoid a gallbladder infection that could potentially spread, among other risks.