Liver
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[[Image:Liver2.png|thumb|150px|left|The location of the liver in the human body]] | [[Image:Liver2.png|thumb|150px|left|The location of the liver in the human body]] | ||
| - | When viewed under a microscope, the liver is seen as large network of units called hepatic lobules. The hepatic lobule is very small and looks like a six-sided cylinder. The actual lobule is surrounded by connective tissue and has about 6 clusters of vessels around the edges. These vessels are | + | When viewed under a microscope, the liver is seen as a large network of units called hepatic lobules. The hepatic lobule is very small and looks like a six-sided cylinder. The actual lobule is surrounded by connective tissue and has about 6 clusters of vessels around the edges. These vessels are branches of the portal vein, hepatic artery, and the bile duct. Through the middle of the lobe is a central vein that is surrounded by cords of liver cells that expand outward in all directions. There are also wide thin-walled blood vessels called sinusoids mixed in with the cords of liver cells. [http://www.janis7hepc.com/Your%20Liver%20Functions.htm] |
=== Ligaments === | === Ligaments === | ||
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=== Lobes === | === Lobes === | ||
| - | The anterior surface of the liver is triangular in shape, and made up of two lobes. The right lobe is the larger of the two, measuring 6 to 7 inches in length. The left lobe is about 3 inches in length. | + | The anterior surface of the liver is triangular in shape, and made up of two lobes. The right lobe is the larger of the two, measuring 6 to 7 inches in length. The left lobe is about 3 inches in length.[http://www.janis7hepc.com/Your%20Liver%20Functions.htm]The falciform ligament is visible on the anterior side of the liver, dividing it into a left anatomical lobe, and a right anatomical lobe. There are also two more lobes. With the liver flipped over, the two lobes are located between the two bigger lobes. They are the caudate lobe and the quadrate lobe. |
== Blood Flow == | == Blood Flow == | ||
Revision as of 04:48, 3 April 2009
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Contents |
Introduction
The liver lies on the right side of the abdominal cavity beneath the diaphragm. It is glossy in appearance and dark red due to the rich supply of blood flowing through it. It is the largest solid organ in the body, weighing about three and a half pounds, and measuring about 8 inches across. It is also one of the most important organs in the body. It plays so many important roles in the body, yet is also the most resilient of all the body's organs. It is even capable of regenerating itself. When part of the liver is removed, it will often grow back to its original size.[1] As little as 25% of a liver can regenerate into a whole liver.
Anatomy
When viewed under a microscope, the liver is seen as a large network of units called hepatic lobules. The hepatic lobule is very small and looks like a six-sided cylinder. The actual lobule is surrounded by connective tissue and has about 6 clusters of vessels around the edges. These vessels are branches of the portal vein, hepatic artery, and the bile duct. Through the middle of the lobe is a central vein that is surrounded by cords of liver cells that expand outward in all directions. There are also wide thin-walled blood vessels called sinusoids mixed in with the cords of liver cells. [2]
Ligaments
Ligaments connect the upper surface of the liver to the diaphragm and the abdominal wall and the under surface to the stomach and duodenum.
Lobes
The anterior surface of the liver is triangular in shape, and made up of two lobes. The right lobe is the larger of the two, measuring 6 to 7 inches in length. The left lobe is about 3 inches in length.[3]The falciform ligament is visible on the anterior side of the liver, dividing it into a left anatomical lobe, and a right anatomical lobe. There are also two more lobes. With the liver flipped over, the two lobes are located between the two bigger lobes. They are the caudate lobe and the quadrate lobe.
Blood Flow
The circulatory system of the liver is unlike that seen in any other organ. Of great importance is the fact that a majority of the liver's blood supply is venous blood. That means that the blood is from the veins. About three-fourths of all the blood that enters the liver is blood from the hepatic portal vein. The remaining one-forth of the blood supply to the liver is from the hepatic artery. The hepatic artery carries oxygen-rich blood from the aorta to the liver.
The blood vessels in the liver subdivide repeatedly until they are tiny capillaries. Each capillary leads to one of thousands of lobules that make up the tissues of the liver. The lobules are made up of hepatic cells, which are the basic metabolic cells of the liver. [4]
All of the venous blood returning from the small intestine, stomach, pancreas, and spleen enters into the portal vein and reaches the liver. This means that the liver gets exposed to basically everything that has been absorbed in the small intestine, where practically all nutrients in the body are taken from. This explains how colon cancer cells can leave the intestine and travel through the portal vein, into the liver, and then grow into tumors. [5]
After collecting and processing all of the gastrointestinal blood that came in through the portal vein, the liver delivers it to the right atrium of the heart through the superior vena cava. [6]
Biliary Flow
Attached to the side of the liver is a small sac-like structure called the gall bladder. The gall bladder is an important structure in the biliary system. During periods of time when bile is not flowing into the intestine, the excess bile gets dehydrated and stored in the gall bladder. [7] The major components of bile include cholesterol, phospholipids, bilirubin (a metabolite of red blood cell hemoglobin), and bile salts. Bile salts act as "detergents" that help digest and absorb dietary fats. Damage to the liver or an obstruction of some kind in the bile duct (called a gallstone) can lead to a serious problems such as cholestasis, steatorrhea, or jaundice. [8]
Functions
The liver has multiple important functions in the body. In fact, most of the functions are all interlaced. It changes food into energy and cleans poisons from the blood whether ingested or inhaled, makes bile to help in the digestion of food, and so many more functions. Another important function of the liver is to produce substances that break down fats, convert glucose to glycogen, and converts ammonia into urea, which is the main substance of urine.
In the presence of severe liver disease, ammonia accumulates in the blood because of both decreased blood clearance and decreased ability to form urea. Too much ammonia in the body can be toxic, especially to the brain.
The liver also makes amino acids and stores vitamins and minerals (vitamins A, D, K and B12). The liver is also responsible for producing 80% of all the cholesterol in the body. By regulating blood levels of substances such as cholesterol and glucose, the liver helps maintain body homeostasis. [9]
The liver also plays an important role in hormonal modification and inactivation. Chronic liver disease may cause hormonal imbalances. For example, the masculinizing hormone testosterone and the feminizing hormone estrogen are metabolized and inactivated by the liver. For someone with liver damage, especially due to alcohol abuse, the result for a man could be the hyperactivity of estrogen which gives them more female characteristics.[10]
Diseases of the Liver
Animal Livers for Food
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References
- Your Liver FunctionsJanis and Friends Hepatitis C Website
- Liver Mama's Health
- Architecture of the Liver and Biliary Tract R. Bowen, June 5, 2004.
External links
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