Thus begins a new series; blogposts to celebrate features of ourselves that are scandalously overlooked. Our internal organs. This will be a collection of pieces drawing attention to our hard-working innards, a compilation that will be barely educational, seldom beneficial, and not even remotely weekly. But I do so love the complex machinations of the bits that make up our bodies, and I thought I would like to write about them.
So first, the kidney. But why does this liver-coloured bean get first place? The gold medal? Let me count the ways.
The kidney is the modest and loyal guardian of the internal milieu. Unlike the flashy lungs, who, at the first hint of acid-base disturbance get all huffy puffy, the kidneys are slow, considered, and in the case of respiratory alkalosis, almost completely capable of returning the pH to normal, a feat the lungs can only dream of. Yes, the lungs may be quick to blow off CO2 in metabolic acidosis, but they bore easily, never quite finishing the job. The kidneys, on the other hand, quietly get on with their lumbering business of bicarbonate and proton shuffling, restoring neutrality without fanfare.
The derivation of the word kidney is joyfully obscure. It comes, possibly, from the root words for belly, womb, and teste. The proto-Germanic (and once again, bless that amusement park of a language) has kidney and testicle freely interchangeable. Allegedly it is also an obsolete, slang term for waiter.
Talking linguistically, when learning of the peripatetic ways of the internal workings of the kidneys and their tubules I first heard the term, and you may well be the same, countercurrent mechanism. What a joy! One could picture the molecules marching in and out of the newly sprouted urine, up and down the nephron, following the concentration gradient the way a retiree with a caravan chases the sun. Marvellous! Evolution is a crazy wonderful thing.
Humans can live perfectly well with a single kidney. Subsequently they have been the source of some fabulous urban myth stories about hand-written notes, telephones, and ice baths. On the sobering side, it means that organ trafficking is a dire global problem. Iran remains the only country where it is legal to sell one’s kidney – a legally traded kidney fetches several thousand dollars, but on the black market prices balloon to hundreds of thousands of dollars.
Your kidney can smell (allegedly). Or perhaps, more accurately, it sniffs at the urine as it gushes by. This marvellous fact was discovered by Jennifer Pluznick, a professor of physiology at Johns Hopkins.
Speaking of receptors, there are, almost definitely, hundreds, possibly thousands of different receptors on each nephron. And there are at least a million of these itty serpiginous pythonesque things per kidney. One can only read this, slack-jawed, and realise that we have barely begun to understand all the functions of this beany beauty. We are but toddlers in our knowledge.
The primary function of the kidney is, of course, to jealously guard the creation of the golden waters – to perfect the concentration of them, compared to plasma. The kidney is the gatekeeper, the demilitarised zone, the border patrol, policing the movement of all manner of molecules, in order to produce a perfectly balanced cocktail of liquid waste.
Allegedly it is edible, with steak, in a good pie, although I think that the human variety may not be the ideal ingredient.
For all its good and wonder though, it is a rather savage stonemason, and concretes small rocks into existence, made from various concentrations of calcium, oxalate, phosphate, uric acid, and cystine. It’s also been known to carve brick red stones out of xanthine, and struvite, which resembles glass crystals and can occasionally be found, disconcertingly, in canned seafood.
The above features are but a tiny fraction of the wonders of the kidney, its function and dysfunction, but it has given me great pleasure to award the kidney the title of top contender for organ of the week. I hope you’ll join me in a round of applause for this sensational viscus, however I’d be surprised if any of you have got this far. Please do add any nephrologically fascinating facts if you’d like.