The Mighty Liver

The liver is one of the largest organs in your body—an adult liver weighs about 3.1 pounds–and is found in the right upper abdomen, below the diaphragm, taking up most of the space under the ribs and some space in the left upper abdomen as well.  Looking at your liver from the outside, the right lobe is larger and left lobe smaller. There is connective tissue separating the two lobes and anchoring them to the abdominal cavity. Liver tissue itself is an intricate network of smaller units of liver cells with many canals carrying blood and bile running in between.

 

One amazing fact about your liver is that it’s the only organ that possesses the remarkable capacity to almost completely regenerate–your liver can regrow back to its full size even after as much as 75% of it has been surgically removed, or injured chemically.  Maybe even more amazingly, in most cases, during regeneration liver function is only partially affected. Detoxification for things like medications is decreased, but many other primary functions are not substantially affected. Because the liver has the job of taking up toxic substances and converting them into harmless substances, or making sure they are released from the body, it is the main site of drug and environmental detoxification in the body. The exposure to chemicals can potentially induce cell death and injury. For the liver to survive this toxic onslaught it has to have this regenerative capability—in other words, liver cells regenerate to prevent its own failure.

 

Why your liver matters . . .

 

Besides being an important center of detoxification, the liver converts the nutrients in our diets into substances that the body can use, stores these substances, and supplies cells with them when needed. Blood coming from all of the digestive organs flows through the portal vein to the liver, carrying nutrients (and toxins). Once they reach the liver, these substances are processed, stored, altered, detoxified, and passed back into the blood or released in the bowel to be eliminated. In this way the liver can, for example, remove alcohol from your blood.

 

The liver plays a central role in all metabolic processes in the body. In fat metabolism the liver cells break down fats and produce energy. They also produce about 800 to 1,000 ml of bile per day. This yellow, brownish, or olive green liquid is collected in small ducts and then passed on to the main bile duct, which carries the bile to the duodenum, or the upper part of the small intestine. Bile is essential for the breakdown and absorption of fats.

 

In the metabolism of carbohydrates, the liver helps to ensure that the level of sugar in your blood stays constant. So, for example, when your blood sugar levels increase or get too high, the liver removes sugar from blood supplied by the portal vein and stores it in the form of glycogen. If your blood sugar levels drop too low the liver breaks down glycogen and releases sugar into the blood. The liver also stores and releases, as needed, vitamins and minerals.

 

Lastly, the liver plays an important role in the metabolism of proteins: it produces the ones that are important in blood clotting (it also breaks down old or damaged blood cells), hepatic cells change amino acids in foods so that they can be used to produce energy, or make carbohydrates or fats. Liver cells also take care of one of the by-products of protein metabolism, a toxic substance called ammonia, by converting ammonia to urea, which is released into the blood to be transported to the kidneys to pass out of the body as urine.

 

SOURCES
Menche N. (ed.) Biologie Anatomie Physiologie. Munich: Urban & Fischer/ Elsevier; 2012.
Pschyrembel W. Klinisches Wörterbuch. Berlin: De Gruyter; 2014.
Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Heidelberg: Springer; 2011.
Michalopoulos, George K. (2013). “Principles of Liver Regeneration and Growth Homeostasis”. Comprehensive Physiology. 3. pp. 485–513
Michalopoulos, G. K.; Defrances, M. C. (1997). “Liver Regeneration”. Science.
Mehendale, Harihara (2005). “Tissue Repair: An Important Determinant of Final Outcome of Toxicant-Induced Injury”. Toxicologic Pathology.
Fausto, Nelson; Campbell, Jean S.; Riehle, Kimberly J. (2006). “Liver regeneration”. Hepatology.
Fausto, Nelson (2000). “Liver regeneration”. Journal of Hepatology.
Chu, Jaime; Sadler, Kirsten C. (2009). “New school in liver development: Lessons from zebrafish”. Hepatology.
Mehendale, H.M.; Apte, U. (2010). “Liver Regeneration and Tissue Repair”. Comprehensive Toxicology. pp. 339–67

 

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