The Ecology of Humans (36-5) The Liver

The Liver

Nutrients pass through the liver before entering general circulation throughout the body. The liver is the largest internal organ of the human body, performing more than 500 functions, including digesting fats, synthesizing proteins, filtering poisons and waste products, storing nutrients, and regulating the levels of many chemicals used by the body that flow through the bloodstream. Some ancient civilizations considered the liver to be where the soul resided.

Most organs have a single blood supply. The liver has 2. The hepatic artery delivers oxygen-rich blood from the heart, providing 25% of the liver’s blood supply.

75% of the liver blood supply is oxygen depleted but nutrient rich, delivered by the (hepatic) portal vein. This vein carries blood that has collected the harvest of digestion. These nutrients are delivered to the liver for further processing and become either immediate fuel or energy reserve.

All other veins in the body flow to the heart, where they are pumped throughout the body. The portal vein is the exception, running to the liver and breaking up into a mesh of tiny capillaries.

The liver is the body’s energy factory, providing glucose: the sugar that fuels the body. When glucose levels are high, the liver pulls excess glucose for storage.

The liver stores energy reserves as glycogen: a carbohydrate made from glucose. Long-term energy storage is put into fat, though not entirely by the liver.

Subject to overwork and abuse, the liver readily regenerates cells. The liver is like the brain in having plasticity: if one section is overwhelmed or damaged, another section performs the functions of the incapacitated area until repaired.

The brain too can regenerate cells. But – as garbage man for the body – the liver has especial need for a fresh change of garment. Hence the liver is adapted to regeneration.

A healthy liver can handle processing a large shot of sugar, converting much into glycogen until later, releasing only a fraction into general circulation as fuel.

An overwhelmed liver is not up to the task, and the body is flooded with sugar. The “sugar burn” from eating excessive sweets is exemplary.

When sugar floods into circulation, the pancreas releases a surge of insulin to tamp the blood sugar level down. Insulin facilitates cells absorbing sugar by increasing the permeability of cell membranes to sugar. Some of the sugar is immediately used, giving a feeling of energy and warmth. The portion that goes unused is converted into energy storage: body fat.

Excessive insulin release floods cells with sugar, sinking the blood sugar level, causing the irritability and weakness of low blood sugar.

Sugar converted to fat by cells for storage is not immediately changed back to fuel. Low blood sugar results in an urge to eat again to fix the hypoglycemia. This begets a cycle of overeating, especially sweets, that causes more eating, leading to being overweight.

The liver is a major protein processor: taking digested amino acid units absorbed by the intestines and reassembling them into various proteins. The liver also distributes amino acids, which cells use to produce whatever proteins are needed there.

The liver may store amino acids, awaiting delivery of further components that make for the complete protein needed. Hence, there is no need to worry about eating complete proteins at a meal if one’s diet is well rounded.

Much of the protein released into the blood and employed by cells is albumin, like that in egg whites. Albumin concentrated in the blood pulls fluids from tissues by osmosis. Therefore, heavy protein consumption invites dehydration.

The liver clears toxins from the bloodstream, including drugs and alcohol, by chemically altering them and excreting them in bile.

Failure to chronically consume and absorb sufficient vitamins and minerals, and other necessary nutrients, cripples liver processing. Poor nutrition means that liver cells are shortchanged of essential nutrition, and poisoned by toxins piling up, waiting for detoxification. The cells began to break down. The bloodstream is then flooded with unprocessed sugars and amino acids, as well as awash in undetoxified chemicals.

Sustained abuse can permanently damage the liver beyond its capability to repair itself. A fine way to accomplish this is by drinking alcohol. Heavy alcohol consumption causes fat deposits to accumulate in the liver.

A prolonged habit of pickling oneself with booze leads to cirrhosis, which is the destruction of liver cells and replacement by scar tissue. Cirrhosis is characterized by diminished flow through the liver. Cirrhosis cannot be reversed.

Liver failure is often the last stage of terminal illness.