Gallbladder is a pear shaped sac that lies on the undersurface of the liver. Its primary function is storage and concentration of bile received from the liver. The capacity of gallbladder to store bile ranges from 30 to 50 ml.
Structure of gallbladder:
For the purpose of description, the gallbladder is divided into three parts: Fundus, Body and Neck.
Fundus is the rounded expanded part of the gallbladder, which usually projects below the inferior margin of the liver. Here it comes into contact with the anterior abdominal wall at the level of the tip of the ninth right costal cartilage.
The body of the gallbladder is directed upward, backward and to the left. It lies in contact with the visceral surface of the liver.
The neck is that part of gallbladder which becomes continuous with the cystic duct. It joins the body with the cystic duct, which eventually joins the common hepatic duct to form the bile duct.
Peritoneal covering of gallbladder:
Gallbladder is completely surrounded by the peritoneum. It completely covers the fundus and binds the body and the neck to the visceral surface of liver.
Relations of gallbladder:
- Anterior abdominal wall
- Inferior surface of liver
- Transverse colon
- First and second part of duodenum
Blood supply of gallbladder:
Gallbladder is supplied by the cystic artery, a branch of the right hepatic artery. The venous blood is drained by the cystic vein directly into the portal vein.
In addition to the cystic artery and vein, several small arteries and veins run between the gallbladder and liver.
Lymph drainage of gallbladder:
The lymph from the organ drains into the cystic lymph node, which is situated near its neck. Afferent lymphatics from the cystic nodes pass to the hepatic lymph nodes and ultimately to the celiac nodes.
Nerve supply to gallbladder:
Sympathetic and parasympathetic fibers reach the organ from the celiac plexus. In addition to the nervous control, the organ is also directly influenced by the hormone cholecystokinin, which is produced by the duodenum.
Function of gallbladder:
As described above, the gallbladder primarily performs the function of storing and concentrating the bile. During breaks between the meals, when digestion is not taking place, the sphincter of Oddi remains closed so that the bile accumulates in the gallbladder. A number of modifications are made to the bile including:
- Selective absorption of bile salts
- Preservation of the bile acid
- Excretion of cholesterol
- Secretion of mucus
To aid in these functions, the surface of gallbladder is thrown in numerous folds that unite with one another and give a honeycomb-like appearance. The cells lining the surface possess numerous microvilli, which also significantly increase the surface area.
When the process of digestion starts, bile is delivered to duodenum as the result of contraction and partial emptying of the gallbladder. The mechanism is initiated by entrance of fatty food in the duodenum. Bile salts in the bile are important in emulsifying the fat, assisting in its digestion and absorption.
Fatty food causes release of the hormone “cholecystokinin” from the mucous membrane of duodenum. The hormone enters the blood and eventually reaches the gallbladder causing it to contract. At the same time, the smooth muscles around the distal end of bile duct and the ampulla are relaxed. This allows the passage of concentrated bile into the duodenum.nters the blood and eventually reaches the gallbladdercontraction and partia