What is the gallbladder?
The gallbladder is a small hollow organ that stores the bile produced by the liver and delivers it into the duodenum.
The medical terms for the gallbladder include:
- Vesica biliaris or vesica fellea (from Latin vesica = bladder; bilis or fel = bile) [4,17]
- Cholecyst (from Greek khole = bile; kystis = bladder) 
Can you live without the gallbladder?
Yes, you can live without the gallbladder. The gallbladder does not produce the bile; it only stores it. After gallbladder removal, the bile constantly flows from the liver into the intestine, which can cause diarrhea in some people.
Gallbladder agenesis is a rare condition in which a person is born without a gallbladder but usually has no symptoms .
Where is the gallbladder located in your body?
The gallbladder is located in the upper right abdominal quadrant. The front part–the fundus–lies under the cartilage of the 9th rib at the bottom edge of the rib cage . It lies under the liver, near its lower border, about an inch medially from the crossing of an imaginary vertical line from the right breast nipple (mammary or midclavicular line) and the bottom edge of the rib cage.
The intrahepatic gallbladder is an anatomical variant in which the gallbladder is completely embedded into the liver .
Shape and Size
- Shape: looks like a pear
- Length: 3-4 inches or 7-10 cm [1,12]
- Width: 1-1.5 inch or 2.5-3.8 cm [1,12]
- Weight: 2.5 ounces or 70 grams, in average 
- Volume: 30-50 mL [5,12]
- (All values are for adults)
Some people have two gallbladders with either one or two cystic ducts .
The gallbladder is a muscular sac, which can be divided into the fundus, body and neck (infundibulum).
The Gallbladder Wall Histological Structure
Gallbladder wall consists of the following layers (from inside out) [1,5]:
- The inner (luminal) surface of the gallbladder consists of a single layer of the columnar epithelial cells, which secrete mucus and absorb water.
- Tunica (lamina) propria is made of connective tissue, which supports the epithelium.
- A muscular layer (muscularis propria) is made of smooth muscle fibers, which contract and push the bile out of the gallbladder.
- The subserosal layer is made of the connective tissue, which strengthens the gallbladder wall.
- Serosa is the outer layer, which is a part of the abdominal membrane (peritoneum); it covers the gallbladder only on its lower side. Serosa contains epithelial cells that secrete a liquid that prevents friction between the gallbladder and other abdominal organs.
The cystic duct connects the gallbladder to the common hepatic duct; the ducts merge and form the common bile duct (Picture 1). All the ducts are made of the fibroelastic tissue, not muscular tissue .
Picture 1. Biliary system: the gallbladder and bile ducts
The flow of the arterial blood: aorta > celiac trunk > common hepatic artery > right proper hepatic artery > cystic artery .
The flow of the venous blood: cholecystohepatic veins > portal vein .
Parasympathetic fibers: the hepatic branch of the Vagus nerve 
Sympathetic fibers: celiac plexus (from T 7-9) 
The lymph from the gallbladder drains to the cystic lymph node, which is often enlarged when the gallbladder is inflamed . Gallbladder cancer can spread to the cystic but also pericholedochal, pancreaticoduodenal, aortocaval, celiac and para-aortic nodes .
The cystic lymph node (Mascagni’s or Lund’s node) lies in the imaginary hepatobiliary or cystohepatic triangle, which has three borders: the cystic duct inferiorly, common hepatic duct medially and the lower liver edge superiorly . This node is often removed together with the inflamed gallbladder.
What is the purpose of the gallbladder and its role in the digestion?
The purpose of the gallbladder is to store and concentrate the bile, which is produced in the liver, and to push it into the duodenum after meals.
The gallbladder is a part of the biliary system, which consists of the ducts that convey the bile from the liver to the intestine. The bile flows from the liver through the hepatic ducts and enters the gallbladder through the cystic duct. After meals, the bile is squeezed out of the gallbladder into the cystic duct and further through the common bile duct into the duodenum. Without the gallbladder, the bile would constantly flow into the intestine, even between meals and at night, which would be a waste.
The bile is a liquid that contains bile acids, which emulsify the fats from the food and thus enable their digestion and absorption in the intestine. The bile also disposes of the bilirubin, which is created in the liver from hemoglobin from the wasted red blood cells.
The Hormones Involved in the Gallbladder Emptying
When the fat-containing food enters the duodenum, it triggers the release of the hormones cholecystokinin (CKK) and motilin from the cells that line the duodenum and jejunum (the first two parts of the small intestine) . Both hormones reach the gallbladder via the blood and stimulate its contraction, which results in the release of the bile into the duodenum .
The hormone somatostatin  and the neurotransmitter vasoactive intestinal peptide (VIP)  relax the gallbladder.
Medications that stimulate the gallbladder emptying include cholestyramine, cisapride, erythromycin and NSAIDs (aspirin, ibuprofen) . Curcumin from turmeric can also stimulate gastric emptying .
Medications that inhibit the gallbladder emptying: calcitonin, loperamide, progesterone.
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