One can easily visualize the liver as an alchemist in their lab, working secretly and passionately on ten different projects at once, surrounded by a vast array of lab equipment, never seeming to take a break. The liver is just like this, always working on many functions at once. Indeed, the liver is a major organ in the body and like the brain, lungs and heart, we couldn’t live without it.
Although the liver is a part of the digestive system, it has so many other key functions (over 500) in the body that it is another physiological system in and of itself, called the hepatobiliary system. Just like the alchemist, transmuting lesser metal into gold, our liver breaks down various molecules into smaller units (catabolizing) and processes nutrients received from digestion to create new compounds (worth more than gold) to support various physiological processes throughout our body. It also stores nutrients for later usage, maintaining proper energy levels, and processing and eliminating toxins and wastes.
The fact that the root of the word liver is ‘live’ in many languages, tells us how important the liver is to the overall function of the whole body. As the key eliminative organ in the body, the liver is quite often the target of herbal therapy, which seeks to remove an encumbrance to vital function by promoting proper elimination. As an old axiom of natural therapy goes, “when in doubt, treat the liver.”
The liver is the heaviest organ in the body, weighing about 1.4 kg in the average adult, and besides the skin, is the largest organ in the body. It is located below the diaphragm, occupying most of the upper right part of abdominal cavity. The accessory organ that participates in the digestive function of the liver is the gall bladder, located in a little depression on the posterior surface of the liver.
Blood flow into the liver is derived from two sources: the digestive tract, which is nutrient-rich low oxygen blood that flows from the digestive tract through the hepatic portal vein into the liver, and from the hepatic artery, which deposits oxygenated blood into the liver sinusoids. The blood from the liver exits into the inferior vena cava through the hepatic vein, which then carries the blood into the heart to be reoxygenated.
When the ampulla vater is closed during periods of digestive inactivity, bile regurgitates into the gall bladder from the common bile duct, where it is stored and concentrated for later use.
Other important functions of the Liver
Carbohydrate metabolism, lipid metabolism, protein metabolism, phagocytosis and detoxification, synthesis and excretion of bile, storage, activation of Vitamin D.
As was previously mentioned, the liver functions as an organ of detoxification, removing, deactivating and eliminating drugs, toxins and hormones from the blood. Again, this is like an alchemist busy in their laboratory, in this case we call it biotransformation: the chemical transformation of a bioactive molecule in the blood plasma into a metabolite that is normally inactive. These metabolic processes have a net effect of chemically altering biologically toxic molecules into more polar compounds, increasing water solubility and thereby increasing elimination by the kidneys.
Biotransformation takes place by enzymatic catalysis, harnessing the activity of enzymes to deactivate a drug, hormone or toxin. Somewhat paradoxically, this enzymatic activity can also be used to activate certain drugs (called a prodrug), such is the case in which codeine is metabolized into morphine.
Just like the alchemist, biotransformative enzymes for drugs, hormones and toxins are very specific and a highly selective process, with particular molecules only being metabolized by one or a few sets of enzymes. Additionally, there are only so many of these enzymes in the liver that can carry out the reactions. Thus, when a particular enzymatic system is saturated (fully utilized) with a particular drug or toxin, the rate at which that particular enzyme system works is at its maximum rate. The rate at which metabolic enzymes are capable of metabolizing a certain concentration of a particular drug or toxin is a relatively constant and predictable rate, only as long as the enzymes are not saturated.
There are four primary patterns of biotransformative activity: oxidation, reduction, hydrolysis and conjugation. The first three activities are often lumped together as Phase I detoxification, while the fourth process, conjugation, is called Phase II detoxification.
We will look at these Phases of detoxification in more detail in our next Blog