On Alimentation…

DE RE FLATIBUS

Of course, this is written on the day after Thanksgiving; the half-time show of Eating Season in America.  Starting with D-50 day, that’s Hallowe’en, when the lil ‘uns try out hyperglycemia, to the New Years Blast, where the calories are something fermentable, we spend the winter stuffing down chow.

Flatulence is a little-honored human behavior.  Actually, it is a vital part of alimentation which is generally unstudied.  Specifically, flatus, or wind, involves the expulsion of rectal gas through the anus, with a merry tweeting sound, and a usually not-so-merry distillate of intestinal fermentation vapors.

Turtles have flatus – as seen on this MRI of a snake-necked turtle.  The transverse intestine appears to have air.  Turtles DO fart: see link.

turtlexrayjpg

Below is a fellow primate:

cassandra-xrays-2

Flatulence is common to the various species.  The common brown lemur demonstrates flatus.  Mother Nature does not usually tolerate the inefficient.  So, starting with the idea that flatus is somehow physiologically beneficial, where do we go with that?

The process of alimentation is ancient and highly conserved.  Mastication, deglutition, catalysis and absorptive digestion are parts of retrieving nutrition from foods; concentration and minimization of waste involves the second part of nutrition.

The large intestine, three sides of a rectangle, takes liquids from the waste succus, the small intestinal liquids, and conserves vital water and salts, without which we would become pathologically dehydrated.

The wily bug Vibrio cholerae simply poisons the Na+/Cl- pumps that drive salt out of the succus, accompanied with physiological water.  Watery liquid passes unresorbed through the colon, manifesting as copious quantities of watery diarrhea.  The thirsty human seeks water, of course – and will even wade into a stream to quench his ravenous thirst.  Gotcha!  says the Vibrio cholerae, returned to the water supply to drift downstream to the next victim.

But here’s the rub.  The busy salt pumps in the colon bring the soluble salts back into the body, and the water follows osmotically.  In such instances where the salts cannot be reuptaken, such as when there is saline Magnesium or polymeric stuff such as polyethylene glycol, Miralax, in the colon, the osmotic uptake cannot proceed.

The salts are replaced by a profuse secretion of mucus, sulphated ploysaccharides which are miscible with water, and form a lubricant that coats the stool, which is formed and shaped by the colon.

But the large intestine would be greatly burdened with moving such a stiff semisolid as stool without the presence of another fluid, which is perfect for movement within – a gas.  Flatus is a space-occupying lubricant which prevents consolidation of stool until it has finished with its twists and turns, and has come down to the rectum for final packaging.

After meals, when the large intestine is active, one frequently notices the rippage of farts.  But the colon is never gas-free; simply look at an x-ray.  And rarely is gas seen in the rectum; it is selectively extruded in a most clever and sensitive manner.  Accidents may happen with watery stool, when the colon cannot tell liquid from gas.

Smile upon the noble fart, even in the elevator.  Your butt is speaking about a billion years of evolution, and winds up the digestive pathway with the final release of this splendid fluid gas, flatus, with a trumpeting glee that bespeaks the triumph of evolution.

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