Around my heart: The Pericardium

A two-walled sac hugs my heart (yours, too).

The pericardium, aptly named:

Peri, or around; Cardion, or heart.

The outer layer – fibrous, rigid – bears the brunt of the work. Holds my heart steady to avoid its swings, tethers it in the expanse of my chest cavity. Keeps it from beating right out.

This layer is tough, just enough for safety purposes. Like the hard peel around an orange, it shields my heart. From infections, so prone to developing in nearby lungs. From my heart itself, which could overfill with blood and too big. My heart may be eager, but this fibrous layer knows everything has its limits.

Inside that hard exterior is an inner layer, cushioned and kind. After all, to do its work, my heart cannot have friction building up with nearby tissues. Even the strongest parts need a bit of softness.

Like anywhere, things can go wrong here, in the pericardium. Fluid can build, cysts can grow, layers can swell. Nothing is perfect. Nothing is guaranteed.

But still my heart pulses. And still my pericardium guards every beat.

Photo by Internet Archive Book Images on Trend hype. No known copyright restrictions

Chatter, click, bite: my teeth

Calcified for strength, longer-lasting than bone. These bits of me are the strongest I have to offer.

My teeth. Twenty-eight in all. (Three of the wisest were lost to the dentist that year after high school; one never appeared.) Iceberg-esque, much of each tooth hides under the surface, roots stretching down to attach to the jawbone. Not bone, but super-strength enamel that covers bone-like dentine that surrounds an inner soft spot for nourishing blood vessels and feeling nerves. Everything is softer on the inside. 

Those pioneers of my mouth - baby teeth - are long gone, beginning to let go at age five and continuing the exodus until I was nearly a teenager, their roots resorbed by my ever-efficient body as the main teeth - permanent aka deciduous - appeared.

Incisors at the front, their chisel-shaped edge that bites and holds. They are my touchy-feely teeth, sensitive enough to identify objects in the mouth with a nibble. Next, the pointed canines, which cut into meat and plastic-wrapped packages. And then the hard-working premolars and molars, their pitted cusps perfectly arranged to grind, to crush.

Teeth are different for every animal: horses have up to 44. Elephant tusks are just extra-long incisors that help with digging. Sharks grow a new set every two weeks. Snake teeth, or fangs, don't chew, but rather  capture prey (and sometimes inject venom). Rodent teeth grow without ceasing.

Paleontologists love teeth for their ability to identify creatures; apparently dentists love them, too.

I'm rather partial to mine. So tonight after I brush them, warding off the warring bacteria trying to turn my last bits of dessert into destructive acids, I will pop in a mouth guard, my best attempt at keeping the worries of life from grinding down the very structures that nourish me.

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pixabay.com

Adrenaline

It happens.

The door flings open. Basement stairs creak. A bear rustles. A cell phone

Pings.

And your brain is on alert. 

Nerve signals are carried from brain to adrenal medulla, which sits prim and proper above the kidney, just waiting to be called into action.

It releases adrenaline, the heavy lifter for extreme pleasure and life-threatening danger. Stress.

First task: make sure energy is at the ready. Nudge the liver and skeletal muscles into breaking down glycogen, encourage fat cells to let go of fatty acids. Sugar and fats now circulate in the blood, ready to be used.

Reappropriation of resources, at its finest.

Mastermind of blood flow changes (with noradrenaline’s help), it makes sure some blood vessels are squeezed while others are opened, rerouting entire rivers so that blood is shunted from skin, digestive organs, kidneys,

and flows freely to the heart, the brain, skeletal muscles.

The heart beats faster. Faster. Faster.

Bronchioles in lungs dilate, pulling in more oxygen.

Faster and more. Faster and more.

Knees knock. Hands shake. Sweat beads.

You are ready.

Within minutes of its release, adrenaline and noradrenaline have primed your body

to react.

Fight off the bear.

Deal with the mortgage.

Answer that text.

As soon as the stress lessens, release of the hormone-neurotransmitter halts. Blood pathways and heart beats return to normal.

But the memory does not disappear. Adrenaline has a way of strengthening long-term memory, making stressful events sit solid in your brain,

your heart.

Still, for the moment, you can catch your breath

and go ahead and answer that text

or just put your phone away.

The Eye

Look at this word.  Then this one.  And think for a moment how it is that you

See.

How your gumball-sized sense organs studded by ears and straddling nose differentiate among 10 million colors, detecting the brightest noontime sun down to a single photon of light.

How an image passes through the clear cornea. Along the colorful iris. Through the gatekeeping pupil, M&M-sized black hole to your soul that it is.

Through the damp aqueous humor and the jelly-esque vitreous body that reminds scientists of egg whites

and lands on the retina.

Where cone cells, 6 million strong in the center of your eye film, detect bright light and colors quickly. And rod cells, 90 million or so along the edges of your field of view, detect low light slowly.

Both important, yet the rod cells are your friends for the deep, dark nights. Slower but more sensitive. Allowing you to see starglow and to pilot submarines.

When light hits, pigments shift, ion channels snap and brain words release,

travelling along the optic nerve

all in a blink of an – well, you know.

Lest you think the optic nerve is too fancy, sending its pitter-patter of information to the brain so three-dimensional images form,

you should know it is also responsible for your blind spot. The blank area in all of your images that your brain somehow fills back in.

To find your blind spot, close one eye and focus – really focus – on one of two dots.  Move your face closer or further and suddenly, the second dot disappears.

Ah-ha. You’ve found it.

Maybe now you can truly see.

Blind spot test. Close your right eye and look at the cross with your left eye. Move closer or further from the screen until the dot disappears. Switch eyes, look at the dot with your right eye, repeat. www.exploratorium.edu/snacks/blind-spot

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Creative Commons/Pixabay | neh.gov | ncbi.nlm.nih.gov

Skin deep

Act I: Epidemermis

Aka - Boundary Line. Death Zone. Bacterial breeding grounds.

This is my boundary line. Where I separate from the outside world. Where I become me.

My outermost layer, very strong wall that it is, virtually impermeable to all on the outside. It keeps the enemies out, and keeps my inside parts in.

The living claim the bottom parts, and then slowly rise, shoved up and pushed out as new life begins below. On their way up, these cells release proteins, lipids, keratin. Strengthening the whole, fulfilling their duty even as they march to their death.

Then, it is time. They die, dry, flake, slough, fall off. Millions every day. I leave tiny bits of me everywhere I go.

And there among the sloughing skin, live my bosom buddies, the bacteria. Thousands of them, crowded in, claiming their plot. In between fingers and toes, inside nostrils and ears, belly button, too. Tucked into the far corners of me and spread along the remaining surface, like a well-iced cake. My skin's flora, as though I am a walking botanical garden. 

More than 80 species reside on the heel; about 40 between the toes; 60 in nail clippings. They munch away at my sweat, releasing the stink under my arms. I am not smelly on my own.

Mostly, my bacteria in residence are good, or at least, they do no harm. They keep the bad guys away, secreting nasty chemicals and calling my immune system into action. But I never  get too comfortable with these nice guys: let some in, and they'll wreak havoc, infecting lungs and bones and gut and joints. 

Intermission: The Basement Membrane

Thin, fibrous sheet. Made by both the layer above and the layer below. Bumpy and folded to allow nutrients to pass from bottom to top. Reservoir for supplies in times of skin repair.

Act II: Dermis

Lots of action here, but we'll be quick. It is Act 2, after all. 

Dense connective tissue that cushions the body. Life-filled cells surrounded by a thick substance that gives strength and snap-ability to the skin. Little ropes and proteins and hyaluronic acid, a third of which is degraded and remade each day.

The necessary bits live here: hair follicles and sweat glands, lymphatic vessels and blood vessels. The dermis is home to many.

Including feeling. The myriad nerve endings that communicate touch and heat and pressure and vibration and more to me. They're how I know to drop the burning pan. How I know that my child's hair is silky smooth. How I know the wet slide of a tear, the tight squeeze of a hug, the warmth of a fire.

Act III: Hypodermis

The grand finale now. The part that holds it all together, attaching the slim skin layers to the muscle and bone beneath. Fat lives here, too, keeping me warm and buffered from winter winds, sometimes making my clothes squeeze tight. If this layer gave up, threw in the towel, quick, then everything else - my boundary with the world - would slip off and fall away.

And I would be lost.

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Creative Commons/Pixabay

The Virus

Life, but not it’s own,

borrowed from another.

A shady spot – chemical or life form or just entirely

different.

Tiny, tiny thing

(millions on a pinhead, for scale).

Mere genes in a protein coat

coming in an array of beautiful shapes and flavors,

all so the virus can pop onto a cell and then enter

without knocking.

Once inside, it commandeers and reprograms the cell’s own hard-earned organelles

making them, eager slaves that they are, do its dirty work:

Copy down the viral recipe. Then use it to make more of the one thing the host cell does not want:

viruses.

Even the ingredients called for belong to the cell:

nucleotides, enzymes, ribosomes, tRNAs, amino acids, DNA mixers, energy.

The virus comes empty handed

and requires everything.

Suddenly, spontaneously, viral bits begin to self-assemble inside the host cell

poor, poor host that it is

And then, hundreds or thousands of the new viruses leave,

exit

usually destroying their host in the process.

The damage is not yet finished

for the new viruses move on to the host cell’s neighbors,

friends and family,

and take them over, too.

Our defenses are strong,

but so are viruses.

That one flu – remember – killed 40 million of us in the span of

two years.

But sometimes we can use viruses,

harness their power

to kill off bacterial infections.

Use the enemy to fight another enemy,

and hope it doesn’t then come for us.

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Creative Commons/Pixabay

On hiccups

Oh diaphragm,

you – hic – dome-shaped mass of muscle just below my lungs

that pulls down to pull in air, relaxes to push it out.

You work – hic – perfectly, most of the time.

Except for now.

Hic.

Did I swallow air or eat too fast or drink too much or – hic – is this merely some result of an amphibian ancestor's gil control? Whatever it – hic – is, it’s annoying. Really.

Caused by your contraction, just half of you (odds say the left) that starts to – hic – suck in air, until that’s cut short when the glottis, which – hic – resides in the small space between my vocal cords, snaps shut.

Wham. Three-hundredths of a second after the air intake starts

it’s – hic – ended so suddenly I make this sound.

Wait for it.

Hic.

Maybe the phrenic nerve, you know, that controls you, diaphragm, and talks with the brain about what’s going on in my neck and body is – hic – irritated. Or the vagus nerve, connected to the larynx, may be upset.

Dare I say the resulting outburst is – hic – childish?

I can – hic – sometimes make you go away. Overload the phrenic and vagus nerve systems or interrupt my breathing.

Bite a lemon, pour a spoon of sugar on the back of my tongue, get scared, hold my – hic – breath.

Often nothing works. Except for a spoon of my friend, peanut – hic – butter.

Cognitive behavioral therapy, one doctor calls it: I control my breathing and think about moving the smooth, nutty food through my mouth and down my throat. And just like that

they’re gone.

Until next time.

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pixabay.com

Hello, my blood

I nicked my finger on a knife

That day before dinner

and while the toddler howled and the dog whined

and peas boiled over and pizza burned,

I watched it:

thin red liquid line.

A few drops of blood.

Millions of erythrocytes – red blood cells.

A staggering loss

except that, at the same moment, 25 trillion red blood cells (minus these few million)

were speeding through my body.

Small disks without a brain or a powerhouse

because there simply isn’t room.

Not when you have a single job: pack yourself with oxygen.

One small red blood cell has 250 million molecules of hemoglobin clasping 1 billion molecules of oxygen.

They hold tight through arteries and blood vessels, until the capillaries, where oxygen – the unsocial, dissociative molecule it is – checks out, goes its own way, to where it’s actually needed.

Red blood cells are designed to not even use the oxygen they carry on their journey.

The body does not like to waste.

These millions of escapee cells, loosed by the slip of my knife will be quickly replaced.

Perhaps death to open air is preferred to being eaten by a phagocytic cell, which would’ve happened anyway after three or four months of constant service – clock in when you’re born and out at your death.

But it wasn’t just red blood cells lost in my carelessness:

there was water

and salts and proteins and hormones and wastes.

And there were the fighters,

those white blood cells always on patrol for enemies, ready to destroy.

Fingers crossed and prayers said they will only ever identify the

real enemies

otherwise, they might just take my whole ship down.

The dog howled again

and I picked up the toddler and

stuck my finger in my mouth

quelling the bleeding (knowing that platelets and fibrin were already doing their sticky work to plug the slender cut)

tasting that metallic, iron flavor

that is the cornerstone

of my life.

I turned off the peas, finger still in mouth,

then dumped the pizza into the trash

and called

for takeout.

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commonfund.nih.gov

nsf.gov, quantitative light imaging gallery

Apoptosis

Cells are programmed to do lots of things... including to die. Below is a tribute to apoptosis, the technical term for self-directed cell death.

Every day, bits of me

Are dying.

I don’t mean figuratively – like lost

Dreams, or hopes, or ideals –

This is not the scenario of a broken winged bird that cannot fly.

Rather, bits of me, quite literally, are dying. Constantly.

Have died every second of every day. 

Will keep dying. On purpose. As planned. For the good of the whole.

Every cell in my body

has a death switch

a big red button, or rather, a miniscule receptor

just waiting for the signal

to kill itself.

When the signal comes, whether before breakfast or after a bath, in the middle of a good movie or under a star-filled sky,

my cell is ready.

My cell already holds all of the components of self warfare.

Fifteen types of enzymes on pause, just waiting to do what they were created for.

And when it’s time, they leap to attention

soldiers on the front lines.

Some, like cytochrome C, are first used in life

Until the switch is flipped, and they become agents of death:

Chopping up DNA

Tearing apart organelles

Fragmenting bits of life

No mercy, no pause, no second guessing.

My chosen cell shrinks and blebs, its parts packaged neatly

In vesicles then left for the scavengers

Which engulf and digest, leaving

No trace behind.

The signal to die can come from a neighbor

Or from inside the cell itself:

If a cell’s DNA is damaged beyond repair, or its proteins have misfolded so much, too much,

Then the cell gives

itself

the signal.

Don’t cry over the death switch for it is

vital to life.

Diseased cells, infected cells, damaged cells,

Cells at the end of their functional life spans –

It would do no good for any of these to let go and simply deteriorate,

Leaking their bits of life all around:

Caustic digestive enzymes

Myriad strange particles.

Anyway, cell death has made me who I am: Without it, my fingers would still be webbed together

Flippers not hands.

Strangely, the death switch is most like a brake.

When the cell is living, the death switch is halting the process of dying.

Which means death is the default.

To be or not to be?

Each cell in my body must ask itself this question every day.

If the answer is not to be, then the work of apoptosis

Or falling off

Or death

Begins.

And life

Follows.

Ode to my heart

It was just February. American Heart Month. A good time to step back and give thanks for this muscular organ that works constantly, every day of our lives.

Design a machine that pumps every second of every day, without stopping ever – not for maintenance or a vacation or just to take a break. Instead, it pumps constantly for 36 years.  37, 38, 80 years, more. Lots and lots of pumping.  A technological marvel.

And that’s what you do, my heart.

You’re the size of my fist. But you pack a big punch. The center of my circulatory system - pump, tubes, fluid. Simple, really.

Push blood to the lungs, where the blood picks up oxygen and drops off carbon dioxide, waste; then push blood out through the body, within a few cell widths of every single cell, so it can drop off oxygen and pick up carbon dioxide, waste. Miles and miles of blood vessels.

I’ve never been around the world, but it’s like my blood goes there every day. Twice. Because there are 50,000 miles of blood vessels in my body. Two trips around the earth, at its equator. All right here.

Pump, tubes, fluid.

Lub-dup, lub-dup, lub-dup.

Beat, beat, beat.

I walk through every day without giving you a second thought. 

But tonight, for just a second, I stop. And I listen. In thanks.

For you, my circulatory system. My blood vessels. My blood. My heart.