The Liver: A Blob That Runs the Body

The Liver: A ‘Blob’ That Runs the Body – The New York Times – By NATALIE ANGIER JUNE 12, 2017

I’m posting this just because I found it fascinating – hope you do too.

To the Mesopotamians, the liver was the body’s premier organ, the seat of the human soul and emotions. The Elizabethans referred to their monarch not as the head of state but as its liver,

Yet even the most ardent liverati of history may have underestimated the scope and complexity of the organ

In one recent study, researchers were astonished to discover that the liver grows and shrinks by up to 40 percent every 24 hours, while the organs around it barely budge. 

After all, a healthy liver is the one organ in the adult body that, if chopped down to a fraction of its initial size, will rapidly regenerate and perform as if brand-new.

the liver’s to-do list is second only to that of the brain and numbers well over 300 items, including

systematically reworking the food we eat into usable building blocks for our cells;

neutralizing the many potentially harmful substances that we incidentally or deliberately ingest;

generating a vast pharmacopoeia of hormones, enzymes, clotting factors and immune molecules;

controlling blood chemistry;

and really, we’re just getting started.

Scientists have also discovered that hepatocytes, the metabolically active cells that constitute 80 percent of the liver, possess traits not seen in any other normal cells of the body.

hepatocytes can enfold and deftly manipulate up to eight sets of chromosomes, and all without falling apart or turning cancerous.

That sort of composed chromosomal excess, said Dr. Markus Grompe, who studies the phenomenon at Oregon Health and Science University, is “superunique,” and most likely helps account for the liver’s regenerative prowess.

The liver is our largest internal organ, weighing three and a half-pounds and measuring six inches long.

The reddish-brown mass of four unevenly sized lobes sprawls like a beached sea lion across the upper right side of the abdominal cavity, beneath the diaphragm and atop the stomach.

The organ is always flush with blood, holding about 13 percent of the body’s supply at any given time. Many of the liver’s unusual features are linked to its intimate association with blood.

Most organs have a single source of blood. The liver alone has two blood supplies, the hepatic artery conveying oxygen-rich blood from the heart, the hepatic portal vein dropping off blood drained from the intestines and spleen. That portal blood delivers semi-processed foodstuffs in need of hepatic massaging, conversion, detoxification, storage, secretion, elimination.

“Everything you put in your mouth must go through the liver before it does anything useful elsewhere in the body,” Dr. Lok said.

the arteries and veins that snake through the liver are stippled with holes, which means they drizzle blood right onto the hepatocytes

The liver cells in turn are covered with microvilli — fingerlike protrusions that “massively enlarge” the cell surface area in contact with blood

Evidence suggests that a similar extravaganza of protein creation and destruction occurs in the human liver, too, but the timing is flipped to match our largely diurnal pattern.

The researchers do not yet know why the liver oscillates, but Dr. Schibler suggested it’s part of the organ’s fastidious maintenance program.

“Hepatocytes are swimming in blood,” he said. “That’s what makes them so incredibly efficient at taking up substances from the blood.”

As the master sampler of circulating blood, the liver keeps track of the body’s moment-to-moment energy demands, releasing glucose as needed from its stash of stored glycogen, along with any vitamins, minerals, lipids, amino acids or other micronutrients that might be required.

The liver also keeps track of time. In a recent issue of the journal Cell, Ulrich Schibler of the University of Geneva and his colleagues described their studies of the oscillating liver, and how it swells and shrinks each day, depending on an animal’s normal circadian rhythms and feeding schedule.

The researchers found that in mice, which normally eat at night and sleep during the day, the size of the liver expands by nearly half after dark and then retrenches come daylight. The scientists also determined the cause of the changing dimensions.

Protein production in mouse hepatocytes rises sharply at night, followed by equivalent protein destruction during the day.

He and others have shown that, through their extraordinary ability to handle multiple sets of chromosomes and still perform and divide normally, liver cells become almost like immune cells — genetically diverse enough to handle nearly any poison thrown at them.

“Our ancestors didn’t have healthy refrigerated food,” he said. “They ate a lot of crap, probably literally, and the liver in prehistoric times was continuously bombarded with toxins. You need every mechanism there is to adapt to that.”

The liver rose to the evolutionary challenge.

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