The liver is the largest organ in the human body, weighing about 1.5 kilograms (3.3 pounds). It is located in the upper right quadrant of the abdomen, below the diaphragm and on top of the stomach, right kidney, and duodenum (the part of the small intestine that connects to the stomach). 

The liver has a complex anatomy, with two main lobes: the right liver lobe and the left liver lobe. The right liver lobe is larger than the left lobe, and it makes up about 75% of the liver's mass. The left liver lobe is smaller, and it makes up about 25% of the liver's mass. 

The liver is also divided into eight segments, which are further divided into thousands of lobules. Each lobule is made up of liver cells, which are the functional units of the liver.

Human Liver Functions

The liver has many functions; the following are the main functions of the liver:

1. Filtering blood: The liver filters all the blood in the body, removing toxins, waste products, and harmful substances, including bilirubin, a breakdown product of red blood cells. This is done through a process called hepatic circulation, in which blood from the digestive tract first passes through the liver before returning to the heart. The liver also helps to metabolise cholesterol, hormones, and drugs.
2. Digestion: The liver produces bile, a yellow-green fluid that helps to digest fats and absorb nutrients in the small intestine. Bile is made up of water, bile acids, cholesterol, and salts. Bile is stored in the gallbladder and released into the small intestine when food is eaten. Bile acids help to break down fats into smaller particles that can be absorbed by the body.
3. Metabolism and detoxification: The liver metabolises (breaks down) nutrients, drugs, and other substances in the body. This process helps to remove harmful substances from the body and convert nutrients into forms that can be used by the body. The liver metabolises fats, proteins, and carbohydrates, these three macronutrients. It helps break down food, fats for energy, synthesise proteins, and store glycogen (glucose). The liver also detoxifies the body by removing harmful substances, such as alcohol and medications.
4. Synthesis of plasma proteins: The liver synthesises (produces) many plasma proteins that are essential for many bodily functions, including blood clotting, maintain blood pressure, immune function, and the transport of nutrients. Some of the proteins that the liver produces include albumin, fibrinogen, and clotting factors.
5. Storage of glycogen, vitamins, and minerals: The liver stores glucose, vitamins A, D, E, K, copper and minerals. Glucose is stored as glycogen, which can be released into the bloodstream when blood sugar levels are low. Vitamins and minerals are stored in the liver for later use and released into the bloodstream when the body needs them.
6. Immunity: The liver plays a role in the body's immune system by producing proteins that fight infection. Some of the proteins that the liver produces that are involved in immunity include immunoglobulins, complement proteins, and cytokines.

The liver is a vital organ that performs many essential functions. It can regenerate itself, so it can usually grow back even if part of the liver is damaged. However, if too much of the liver is damaged, it can lead to Hepatitis, Cirrhosis and Liver cancer, which is a life-threatening condition.