What does your liver do?

TRISH LALOR: Hello everyone. In this introductory video, we’d like to give you a quick overview of the functions of your liver. If you are interested to explore liver biology in more detail, you might consider signing up for the next run of our previous course on liver disease, which is also hosted here on FutureLearn. In the meantime, we’ll give you the basics here to help you understand what goes wrong when a liver fails and a patient requires transplantation. Your liver is your largest internal solid organ, weighing in at about a kilogramme and a half in an adult. Although, it does grow to fit your size.

It is situated slightly to the right of your body under your rib cage and held in place by the diaphragm and intra-abdominal pressure. It’s connected to the rest of your body by two main systems, the blood supply and the drainage of bile, which we will show you in more detail in later activities. Now we’re going to zoom in to a picture of a real liver. So if you don’t want to see one, close your eyes for a second. So this is a picture of a diseased liver, which was collected as part of the transplant programme in Birmingham. Oxygenated blood from the body enters through the back of this liver via the hepatic artery.

This is around where the blue arrow is. But interestingly, because your liver has major roles in digestion, there is another supply which also enters the liver from the abdominal organs. This vessel takes food materials directly from your intestines to the liver. And it’s called the hepatic portal vein. Blood from both of these inputs mixes in the main body of the liver and then leaves via the hepatic vein for return to the systemic circulation. There is also a connection which drains bile from the back of the liver into the gallbladder. This is indicated by the white arrow. And the bile is stored here until it is required.

This gallbladder is a kind of muscular bag about 10 centimetres, or four inches, long. OK, if you’ve had your eyes closed, now you can open them. So we touched on digestion there. So let’s consider some of the main roles the liver fulfils for you. If we take digestion first, the liver stores and processes materials that you ingest. So sugars in your diet can be used for energy throughout the body. Or they can be stored as a polysaccharide called glycogen within the liver tissue. This can then be released as glucose for fuel whenever necessary. Vitamins, minerals, and useful fats can also be stored within the liver or used here as building blocks for making useful materials.

So the liver is a bit like a factory that makes useful proteins for your body. One of these is albumin, which is a very useful transport molecule which helps carry useful materials around in your bloodstream. Also, the proteins which help your blood clot, the so-called coagulation factors, are made within your liver. Your liver factory also recycles materials from elsewhere to make useful products. One of these, bilirubin, is made from the breakdown of old red blood cells when they are no longer needed. This bilirubin is transported to the liver bound to albumin. And you can see the blood vessels at the back of this liver in red in this picture.

The liver then chemically modifies this bilirubin so that it becomes water soluble and can be transported into bile, which is stored in the gallbladder as we mentioned, until it is needed to help emulsify fats in your intestines. Then it would be squeezed and secreted along the common bile duct, which is shown in green in this picture, and into the intestines. Now, this is important. Because many useful vitamins are fat soluble. And also, many useful fats are found in your diet. So these need to be extracted to be used by the liver. Bilirubin can also be excreted via urine and faeces once it is made water soluble by the actions of the liver.

The bacteria in your intestines also contain enzymes which can modify bilirubin in a similar way to help with this excretion. Now, we’ve mentioned these enzymes or proteins that help with chemical reactions, which are found within your liver and help processes such as the conjugation of bilirubin I just mentioned. But there are other enzymes here too, which help to synthesise and break down fats and sugars for either storage or use. And other enzymes in the liver facilitate another of its important roles– the detoxification of chemicals and substances that enter your bloodstream or are generated in situ by metabolism.

Prescription drugs, food additives, cosmetics, alcohol, any chemical substance is processed within your liver to break down and utilise anything that’s useful for the body and to permit the excretion of waste chemicals into urine, faeces, or bile. All of these complex processes are carried out by a variety of specific and very different cell types found within the liver. We’ll learn more about these in the next couple of activities. But in the meantime, when you consider all of these important roles in digestion, detoxification, the manufacture of useful chemicals, and bile production, it’s easy to see how devastating it would be for your body if your liver stopped working.