Lesson 1, Topic 1
In Progress

01-Metabolic Function of the Liver

March 28, 2021

Metabolic function of the liver
As we discussed in Chapter 18, the liver plays an important role in mechanical digestion of lipids because it secretes bile. Recall that bile breaks large fat globules into smaller droplets of fat that are more easily digested by the enzyme lipase.

In addition, the liver performs many other functions necessary for healthy survival. The liver plays a major role in the metabolism of all three main types of nutrients.
For example, the liver helps maintain a normal blood glucose concentration for a few hours after a meal by storing glucose when it is overly abundant then releasing the glucose into the blood as needed. Many complex chemical reactions, regulated by many different hormones, assist in these storage and release processes.

Liver cells also carry out the first steps of protein and fat metabolism. Liver cells also synthesize several kinds of proteins. These proteins, when released into blood, are called the blood proteins, or plasma proteins. Prothrombin and fibrinogen, plasma proteins formed by liver cells, play essential parts in blood clotting (see p. 365). Another plasma protein made by liver cells, albumin, helps maintain normal blood volume.

The liver can also detoxify the body of toxic substances such as bacterial products and certain drugs. Once detoxified, these chemicals are often easier to excrete from the body. The liver can also store several substances, notably iron and vitamins A and D.

The liver is assisted by an interesting and unique structural pattern of the blood vessels that supply it. Recall from Chapter 15 that the hepatic portal vein delivers blood directly from the gastrointestinal tract to the liver (see Figure 15-11). This arrangement allows blood that has just absorbed nutrients and other substances to be processed by the liver before being distributed throughout the body. Thus excess nutrients and vitamins can be stored and toxins can be removed efficiently from blood arriving from the GI tract—before the blood reaches other areas of the body.