The liver serves many different functions in humans and animals of similar physiology. In addition to detoxifying the blood, the liver also synthesizes, or builds, important macromolecules. It's a storage warehouse for sources of emergency energy. Finally, it breaks down certain hormones and components of blood, and recycles the molecular components for use in other molecules.
Significance
The liver is vital, and humans can't live without it. Intriguingly, notes Dr. Lauralee Sherwood in her book "Human Physiology," it's one of the only human organs known to regenerate if a lobe is damaged or removed. The major functions of the liver are generally blood-related--it cleans and purifies the blood, while storing certain blood components and breaking down others. It's part of many different body systems because of its multiple roles in physiology.
Features
Certain liver features provide insight into its function. The liver, for instance, is made up of cells that produce unique enzymes. An enzyme, explain Drs. Reginald Garrett and Charles Grisham, is a biological catalyst, meaning a protein-based molecule that assists chemical reactions in taking place more rapidly than they would in the absence of the catalyst. Liver enzymes collect excess sugar from the blood and process the sugar into a storage molecule called glycogen. Liver enzymes also help break apart glycogen to increase blood sugar during periods of fasting.
Effects
Some liver functions have visible effects. For instance, the liver breaks down the protein in red blood cells that delivers oxygen from the lungs to the tissues. This protein, called hemoglobin, is made up of many valuable molecular components that need to be recycled as many times as possible--the liver assists in this. Other components of hemoglobin breakdown represent metabolic waste, and the liver disposes of them via the bile. If the liver is malfunctioning, notes Dr. Sherwood, one of these products, called bilirubin, can turn the skin yellow, indicating jaundice.
Considerations
The liver doesn't simply process products of digestion, it also aids in digestion. Dr. Gary Thibodeau, in his book "Anatomy and Physiology," notes that the liver makes bile, which the gallbladder secretes into the small intestine. Without bile, the pancreatic enzymes secreted into the intestine wouldn't be able to digest dietary fat, which would result in malabsorption of both fats and fat-soluble vitamins. As such, the liver plays a vital role in absorption of nutritional molecules.
Expert Insight
Certain liver functions shared by both humans and animals make the liver not only valuable to its owner, but also a valuable source of nutrition to other animals. Humans and other mammals, for instance, store many vitamins--including vitamin A, D, and B12--in the liver, notes Dr. Sherwood. As such, liver is a rich source of these vitamins if consumed. Humans in some cultures consume livers from cows and other animals in order to obtain these valuable vitamins.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
