The liver is the largest organ within your body and constitutes the hepatic system. The hepatic artery and hepatic portal vein carry oxygen and nutrient-rich blood to the liver, while the hepatic vein transports blood from the liver back to the heart. The overall function of the liver is to promote body homeostasis. In other words, your liver works to keep your body operating at optimal level. It does this through blood circulation, nutrient breakdown, detoxification, secretion and elimination of waste products.
The liver is a major player in the overall function of the circulatory system. The liver is often likened to a checkpoint. Substances that enter the body through the small intestine are first screened by the liver. If those substances are found to be beneficial, they are allowed to circulate to the rest of the body's organs. But if those substances are harmful, the liver is able to isolate and rid the body of them before they damage other internal organs.
Every bit of food and drink you swallow eventually makes its way to your liver from your small intestine via the hepatic portal vein. Special cells called hepatocytes convert proteins, fats and carbohydrates into a sugar called glucose. Glucose is what fuels the body. Whenever you consume something, the nutrients in that food are broken down and stored directly in your liver as glycogen. When blood glucose levels are too low, your liver releases some of that stored glycogen back into the bloodstream as glucose. In addition to synthesizing glucose, the liver is also responsible for converting excess proteins and carbohydrates into triglycerides and fatty acids. The liver also removes and stores iron and some fat-soluble vitamins from the blood.
Because not everything you eat or drink is completely safe or healthy, your liver is tasked with the important job of acting as the body's detoxification center. Imagine that your liver is like a sieve. Between the many rows of cells in your liver are spaces where your blood is filtered. Special phagocytic cells, called Kuppfer cells, collect and help rid the body of toxins such as alcohol and residual food pesticides. These cells can either convert harmful materials into less toxic substances, or they can repackage them for elimination. Even though your liver does a pretty good job of separating beneficial nutrients from harmful substances, an overload of toxins can take its toll. It's important to boost your liver function by eating foods rich in antioxidants or by supplementing your diet with folate, vitamins B-12 and B-6, as well as vitamins C and E.
Bile is a fluid that is secreted by the liver and stored in the gallbladder. Bile is composed mostly of water, electrolytes and organic molecules, and it is necessary to aid in the digestion and absorption of fats and fat-soluble vitamins in the small intestine. The secretion of bile is important, because it plays a major role in the elimination of excess cholesterol.
Another important function of the liver is elimination of wastes and toxic materials. For example, bilirubin, which is a toxic by-product of hemoglobin, must be eliminated through bile in feces or urine. Kuppfer cells in the liver first pick up old blood cells. Available iron is recycled, but whatever is left over from the red blood cells is converted into bilirubin. If bilirubin is not properly and efficiently eliminated, it results in the yellowing appearance of the skin and eyes, also known as jaundice. The liver also rids the body of ammonia by converting it to urea, which is then eliminated in urine.