Introduction to the Gallbladder
When it comes to digestion, there are different stages that occur before a finished product is “released”. Many different chemicals and enzymes work to absorb energy from the food we eat. One of these enzymes is bile.
The Biliary Tree
Bile is a fluid that is mostly made out of water. Along with water we also see organic and inorganic salts, fats, and bilirubin. Bilirubin is the byproduct of red blood cells that are damaged or old. One in the liver, bilirubin is converted into a water-soluble form. Most bilirubin is excreted from the body in urine or in feces, but some is kept behind to help form bile and may be used in other processes in the body.
In humans and most vertebrates, bile is formed in the liver. Once produced, bile flows down the biliary tract, also called the biliary tree. Often called a tree because of its appearance, the biliary tract consists of two ducts that come out of the liver. The left and right hepatic ducts join together to form a larger duct called the common hepatic duct. Shooting off of the common duct is the cystic duct. This duct allows passage of bile into the gallbladder. The common hepatic duct and the cystic duct then join at the common bile duct, which then ends in the duodenum, the large intestine. With all of these passages and ducts, you can see why it is referred to as a tree.
The Function of the Gallbladder
The main function of the gallbladder is to concentrate and store bile. When bile leaves the liver, a portion of it is sent directly to the large intestine. The other portion is redirected from the common bile duct to the cystic duct where it is then stored in the gallbladder. The gallbladder can store around 100 ml of bile. While inside the gall bladder, 90% of the water it contains is reabsorbed into the body. This creates a thick fluid that will aid in digestion.
Whether or not the gallbladder receives bile is dependent upon a muscle called the Sphincter of Oddi. This circular muscle resides just below the stomach at the end of the common bile duct. When we eat, after the food leaves the stomach and enters the small intestine a series of electrical and chemical impulses cause the muscles of the gallbladder to constrict and the sphincter of Oddi to relax. This series of actions causes bile to rush through the common bile duct and into the small intestine where it serves to digest food.
Structure and Location of the Gallbladder
The gallbladder is constructed like most organs in the digestive tract it contains:
- Inside Layer: The inside of the gallbladder is comprised of columnar epithelium cells. This is very similar to the intestines and the stomach.
- Lamina Propria: The next layer is a layer of loose connective tissue called the lamina propria. Together the propria lamina and the columnar epithelium make the mucous membrane.
- Smooth Muscle: The next layer in the structure of the gallbladder is a layer of smooth muscle. Smooth muscle is involuntary muscle that lines most autonomous organs. Around the muscle is a layer of connective tissue aptly called the peri muscle.
- Serosa: The outermost layer of the gallbladder is the serosa. This is the lining of the gallbladder that contains blood vessels.
The gallbladder is divided into three sections. The largest portion of the gallbladder is referred to as the fundus. This portion sits inside the liver. The next section is the body which is the longest portion. The last section is the neck. The neck tapers down into the cystic duct but does not do so in a perfectly symmetrical way. There is a little pouch that sticks off of the neck where gallstones commonly get stuck called the Hartmanns pouch.
If we look inside the gallbladder while it is deflated we will see anatomic structures known as rugae. Rugae are folds of tissue that allow an organ to stretch and contract and maintain its shape.
The gallbladder can be found on the right side of the abdomen. It is placed just below the liver. The gallbladder inflates and deflates like a balloon. When it is fully inflated it can measure 8 centimeters long and 4 centimeters round.
Located on the right side of the abdomen, this pear-shaped organ sits just below the liver and to the right of the pancreas and the large intestine.
Development
The gallbladder begins to take shape at around the fourth week of gestation in an embryo. You can see the development of the gallbladder along with the liver in what is called the hepatic diverticulum. The hepatic diverticulum is also called the liver bud because of its plant-like appearance. The liver bud is located in the endodermal cellular layer of the embryo.
The gallbladder is one of many organs that is measured all throughout pregnancy. Until around the 12th week of development, the gallbladder is a solid organ. At 12 weeks bile begins to form and the gallbladder begins to serve its purpose. From the 15th week of gestation to birth, the size of the gallbladder and the size of the fetus will both grow equally in proportion to one another. This is one reason why the gallbladder is measured throughout pregnancy. Proper growth rate can confirm proper fetal development and also give an idea about the gestational age of the fetus.
Gallbladder Disorders
Although very useful for storing and concentrating bile, the gallbladder is not an organ that humans necessarily need to live. While concentrated bile is helpful to break down fats and cholesterol, the gallbladder can be removed from the body. This procedure is called a cholecystectomy. In this procedure, the gallbladder and cystic duct are removed. Bile is no longer diverted from common bile duct and bile flows directly into the small intestine.
For it being such a small organ it can cause a person a lot of grief. Pain that is caused by gallbladder problems can mimic heart attacks and is sometimes compared to childbirth.
Some common gallbladder disorders are:
Gallstones
Gallstones are concentrated deposits that can be found inside the gall bladder. They are usually painless until they become lodged in a bile duct. Many factors can contribute to gallstones including age, diet, and health problems. There are three kinds of gallstones:
- Cholesterol Stones: Cholesterol stones are the most common form of gallstones and are greenish-yellow in appearance.
- Brown Pigment Stones: These small dark stones are described as being oily and soft because they are made up of fatty acids along with bilirubin.
- Black Pigment Stones: These stones are small and dense. Black Pigment Stones are usually the result of a liver disorder.
Cholecystitis
Cholecystitis is the inflammation of the gallbladder. This is usually the result of kidney stones. It is also possible that other gallbladder problems may cause inflammation, such as infection or parasites.
Cholestasis
This is the stopping of the flow of bile in the bile ducts. There are many things that can cause this, including a stone block a point in the biliary tree, narrowing of the biliary tree, inflammation of the pancreas and problems inside the liver. Signs of a bile blockage can be seen in other systems of the body. The eyes of someone with cholestasis will have a yellowing tint and they may experience skin irritation.
Gallbladder and Biliary Cancer
Cancer can occur in either of these places. Liver cancer or pancreatic cancer may also cause problems with the gallbladder.
Consult your physician if you suspect you may have any one of these issues. If you experience abdominal pain for more than six hours then it would be wise to at least make an appointment with your doctor. During examination, the doctor may look for what’s called Murphy’s sign. Murphy’s sign is found by hooking your fingers under the bottom of your ribcage on the right side of the abdomen. Exhale and breathe in. Do it again on the left side. If you experience pain while inhaling on the right side and not the left then it is considered a positive Murphy’s sign and you may have cholecystitis.
Maintaining a Healthy Gallbladder
Diet and hydration are important to keep your gallbladder healthy. If you start experiencing acute episodes of gallbladder pain limit your intake of fatty foods. Also, try to eat more vegetables, grains and lean meats.
