The gallbladder or gallbladder is an organ of the digestive system responsible for the accumulation and concentration of bile, a yellow-greenish liquid produced by the liver in order to facilitate the digestion and absorption of fats and fat-soluble vitamins, and neutralize the acidity of the chyme coming from the stomach.
The task of the gallbladder is precisely to accumulate bile during fasting, pouring it into the initial part of the small intestine after meals. This "reservoir", also known as gall bladder, is a hollow piriform organ, 7-10 cm long by 2.5-3.5 cm wide and 1-2 mm thick. The capacity of the gallbladder is estimated at about 30-50 ml, but it can increase in pathological conditions, considering the distensibility of the wall.
The gall bladder is housed in a depression, called the cystic dimple, on the lower face of the liver and can be anatomically divided into three portions - which from right to left, from bottom to top and from front to back - take the background name (more dilated), body (more voluminous) and neck (narrower). This last part of the gallbladder continues in the cystic duct, a 3/4 cm long channel that joins the hepatic duct to form the common bile duct.
The internal surface of the gall bladder is covered by a mucosa raised in folds, variable in height depending on the state of distension of the bowel. Some of these folds, however, are constant and fixed, especially at the level of the neck, where they form the so-called spiral folds or valves. At this level the muscular layer also thickens, without producing a real anatomical sphincter, but a structure similar to it from the functional point of view. The gallbladder mucosa has a cylindrical epithelium, supplied with microvilli at its distal end (very important, given the need to reabsorb water and electrolytes through the cystic walls). The contraction of the gallbladder - allowed by the muscle bundles that make up the smooth muscle layer underlying the mucosa - determines the passage of bile into the intestine.
Several gastrointestinal hormones carry out an important action on motility and consequent emptying of the gallbladder, acting simultaneously on the tone of the sphincter of Oddi. The best known is the cholecystokinin (CCK), which is secreted by the duodenal mucosa in the presence of chyme, especially when it is rich in fat. As the name itself reminds us, this hormone stimulates the emptying of the gallbladder, stimulating its contraction and favoring the relaxation of Oddi's sphincter; also secretin, gastrin, neurotensin and pancreatic polypeptide perform a favoring action, while somatostatin, VIP (vasoactive intestinal peptide), glucagon and calcitonin hinder the activity of the gallbladder. The activity of this vesicle is also regulated at the nervous level through sympathetic and parasympathetic afferents.
Inside the gall bladder, as in any other biliary tract, calculus ("pebbles") can form. When these concretions produce symptoms and cannot be eliminated by drugs or "bombardment" with ultrasounds, surgical removal of the gall bladder (cholecystectomy) may be necessary; being a non-vital organ, the patient's health is no longer compromised (at most he can complain of gastrointestinal disorders, such as steatorrhea and diarrhea, especially after eating high-fat meals). Cholecystectomy may also be necessary in the presence of gallbladder cancer, which however has a very low incidence in the population.
