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The Liver

Table of Contents
The Lungs
The Trachea
The Testes
The Submaxillary Gland
The Liver
The Stomach and Duodenum
The Blood
The Arteries and Veins
The Adipose Tissue
The Skin
The Pituitary Gland
The Pancreas
The Thyroid
The Kidney
The Spinal Cord
The Cerebellum
The Elastic Cartilage
The Bone
The Smooth Muscle
The Striated Muscle


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The liver, which is one of the largest organs in the body, and is the largest gland, is one of the most important organs in the human system; without it, a human would die within one day.


The liver works in the digestive system, the excretory system, and the circulatory, and, as a result, is a multifunctional organ. The liver works primarily as a filter for blood during the digestive and excretory processes. After food is eaten, the blood from the digestive organs is drained into the liver via the hepatic portal vein, where it can be filtered before it makes its way to the rest body. The liver removes some of the excess nutrients and solutes that are found in high concentration after digestion, and releases some back into the blood as it continues its journey around the body.


The liver works in conjunction with the pancreas to control blood sugar levels in the tissues and the blood. After a meal, the blood is filled with glucose molecules, and in response to the insulin secreted from the pancreas, the liver removes the excess glucose from the blood and combines it to form larger molecules called glycogen, which is stored in the liver (glycogenesis). When the glucose levels in the blood drop as a result of cellular metabolism, the pancreas releases glucagon, and the liver reacts appropriately, breaking its glycogen stores down into glucose and releasing it back into the bloodstream (glycogenolysis). The liver can also make glucose from proteins and fats if both glycogen stores and glucose levels are low (gluconeogenesis).


The liver is also responsible for the production of bile, a yellow-green solution that contains bilirubin, a byproduct of hemoglobin, bile salts, cholesterol, electrolytes and phospholipids. Bile is essential in the physical breakdown of fat particles into smaller pieces, called emulsification. When fats enter the duodenum, hormones are sent which trigger the release of bile from its storage center, the gall bladder.


Finally, the liver is responsible for the natural production of cholesterol, a steroid essential to the production of cell membranes, the formation of hormones and vitamin D, and the production of bile salts.