The Anatomy of the Gallbladder

This organ stores and releases bile for digestion

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The gallbladder is a small, pear-shaped hollow organ, located just below the liver on the right side of the body. The gallbladder forms a reservoir to store bile, also known as "gall," which is linked to the origin of its name. It is a muscular organ that contracts when bile is needed, forcing the bile through the cystic duct. The main function of the gallbladder is to store and concentrate bile (which is produced in the liver) as well as to release bile into the digestive system. 

What is Bile?

Bile is a greenish-brown alkaline fluid (consisting of waste products, cholesterol, and bile salts). Bile is not a digestive enzyme, but, the bile salt functions in a similar manner, in that it emulsifies large fat droplets. Bile’s primary function in the digestive system is to breakdown fats. Bile is secreted from the gallbladder (where it is stored) then enters the small intestine in response to a hormone called cholecystokinin (which gets released when food enters the small intestine from the stomach). Once bile enters the duodenum (the first section of the small intestine) it goes to work breaking down ingested fat, as well as fat-soluble vitamins, improving the ingested solubility of digested fat, facilitating its absorption.

Bile is what gives feces its brown color. The end location for bile is with the feces through the anus.

Anatomy

The gallbladder is located in front of the duodenum (the first section of the small intestine). It is approximately an inch wide and 3 inches long, tapered at one end where it connects to the cystic duct. It has the capacity to store approximately 30 to 50 cubic centimeters (cc) of fluid, called bile.

Structure

The gallbladder is divided into three sections, including:

  • The fundus—the large rounded base which stores the bile juices, the fundus comprises the distal (far end) portion of the gallbladder, which is angled, causing it to face the abdominal wall
  • The body—the part of the gallbladder that begins to taper into the neck.
  • The neck—the area where the gallbladder continues to taper, becoming narrow as it joins the cystic duct (which leads into the biliary tract).

The neck of the gallbladder has a folded area of tissues called “Hartmann Pouch.” This is an area—located at the junction of the neck of the gallbladder and the cystic duct—where gallstones commonly become stuck, causing a decrease in bile flow (cholestasis).

There are several layers of the gallbladder, these include:

  • The epithelium—a thin layer of cells that lines the inside of the gallbladder.
  • The lamina propria—a layer of connective tissue; when this layer is combined with epithelium, it forms the mucosa (a membrane that lines body cavities and covers organs)
  • The muscularis—a layer of smooth muscle tissue that enables the gallbladder to contract to release bile into the bile duct.
  • The perimuscular—a fibrous connective tissue layer, that surrounds the muscularis.
  • The serosa—a smooth membrane that forms the outer covering of the gallbladder.

The outer layer of the gallbladder's fundus and other surfaces of the gallbladder—those that are not in direct contact with the liver—are covered by a type of tissue called serosa. The serosa is a type of tissue that lines internal cavities and forms a smooth, two-layered membrane, lubricated by fluid. Serosa contains blood vessels and lymphatics (vessels similar to veins that are part of the lymphatic system). The function of lymphatics is to transport lymphatic fluid from the lymph nodes.

The surfaces of the gallbladder which are in contact with the liver are not covered with serosa, but, rather they are covered with connective tissue.

Location

The gallbladder is located inferior (below) and posterior (behind) to the liver in the upper right quadrant (section) of the abdomen. It lies in front of the duodenum (the first section of the small intestine). The gallbladder is connected to the liver via the ducts known as the biliary tract.

The gallbladder is attached to the digestive system by a system of hollow ducts called the biliary tree. The gallbladder, bile ducts (tubules in which bile travels through) and associated structures (which are responsible for producing and transporting bile) comprise what is called the “biliary system.” This is sometimes referred to as the biliary tract.

Through this system, bile flows from the liver (where the liver cells make and secrete the bile) into a system of ducts—located inside and outside the liver—which allow the bile to flow from:

  1. The right and left hepatic ducts
  2. Drain into the common hepatic duct
  3. Bile flows from the common hepatic duct, which joins the cystic duct from the gallbladder, forming the common bile duct
  4. The common bile duct runs from the liver to the first section of the small intestine (the duodenum) where some of the bile is excreted to help breakdown fat. Note that 50% of the bile that flows through the common bile duct is stored in the gallbladder.

After food is eaten, a hormone called cholecystokinin is secreted; this stimulates the release of bile, and the bile begins breaking down fats in the digestive system.

Anatomical Variations

Examples of anatomical variations of the gallbladder include:

  • Agenesis is an absent gallbladder.
  • Double gallbladder may be seen, with one common duct or two separate cystic ducts.
  • Phrygian cap is the most common congenital (present at birth) anatomical variation of the gallbladder, involving an abnormality of the fundus.

Function

There are several important functions of the gallbladder which include:

  • To store and concentrate bile
  • To respond to intestinal hormones (such as cholecystokinin) to empty and refill its bile stores
  • To contribute to regulating the composition of bile (the percentage of water, bile salts and more)
  • To control the flow of bile into the small intestine
  • To contract (secreting bile into the biliary tract and duodenum)

The contractions of the gallbladder are caused by several factors, including:

  • Fatty food content, combined with gastric distension (outpouching of the stomach due to a high volume of food content)
  • The release of cholecystokinin (CCK) from the duodenum

Function of the Biliary System

There are several important functions of the biliary system, including:

  • To drain the liver’s waste products into the first section of the small intestine (called the duodenum)
  • To secrete bile (in a controlled release fashion) which aids in digestion of fats during digestion

Bile has two primary functions, including:

  1. To carry away waste
  2. To break down fats

Associated Conditions

Common gallbladder conditions can involve infection, stones, inflammation or blockage of the gallbladder.

Gallstones (cholelithiasis) are pebble-like deposits of bile in the gallbladder. They can be very small (such as the size of a grain of sand) or as big as a golf ball. They can accumulate as a single gallstone, or as a collection of many stones, of various sizes. There are two types of gallstones, including:

  • Cholesterol gallstones (made of undissolved cholesterol, are yellow in color and the most common type)
  • Pigment gallstones (dark brown or black stones which result from too much bilirubin in the bile)

Other conditions include:

  • Cholecystitis (inflammation of the gallbladder)
  • Chronic (long-term) acalculous gallbladder disease (a condition involving the gallbladder’s inability to contract and empty bile)
  • Gangrene of the gallbladder (death of tissue in the gallbladder which is the most common symptom of untreated conditions such as cholelithiasis, or in those with diabetes)
  • Abscesses of the gallbladder
  • Congenital defects (conditions which are present at birth) of the gallbladder
  • Sclerosing cholangitis (progressive condition of the liver and gallbladder, resulting in scarring and blocking of the bile ducts)
  • Tumors of the bile ducts or gallbladder

Treatment

Once a diagnosis of gallstones (or other gallbladder disorders) is made, most people with symptoms undergo removal of the gallbladder. this procedure is called a cholecystectomy. This procedure is most often performed using laparoscopic (use of a scope with a camera, which is inserted into a very small incision) surgery. Laparoscopic surgery is also called minimally invasive surgery, because of the small incision. Today, one of the most common robotic-assisted surgery procedures is a cholecystectomy. One of the most common surgeries performed worldwide is the removal of the gallbladder (cholecystectomy) as a treatment for gallstones.

Potential Health Problems Following Gallbladder Removal
Verywell / Cindy Chung

Tests

Tests performed to diagnose gallbladder conditions may include:

  • Liver enzyme tests are blood tests which may be elevated when severe inflammation is present, may also indicate the possibility of gallstones)
  • A complete metabolic panel (CMP) blood test may show an elevation in bilirubin levels when there is an obstructed bile duct.
  • A complete blood count (CBC) blood test may indicate acute cholecystitis when the white blood cells are elevated
  • Ultrasound (test of choice for cholecystitis, can accurately show if there are signs of inflammation and/or if gallstones exist) 
  • Computed tomography (CT) scan—a detailed X-ray image of the gallbladder
  • Magnetic resonance imaging (MRI) is often done during an emergency examination when a person complains of unexplained abdominal pain.
  • X-rays of the abdomen
  • Endoscopic retrograde cholangio-pancreatography (ERCP) involves endoscopy. A tube with a camera that is inserted into the throat and down the esophagus into the stomach then into the small intestine, a dye is injected into the gallbladder ducts, liver, and pancreas so the organs can be clearly viewed on an X-ray.
  • A hepatobiliary iminodiacetic acid (HIDA) scan with cholecystokinin (CCK) is a test involving the administration of cholecystokinin to stimulate the gallbladder. Next. images are taken of the gallbladder before and after the CKK is given to evaluate how well the gallbladder contracts.
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