Tag Archives: blood

Our blood too rich

mosquito_cropped

I choose today, when most of us in New England are sunk under wet snow and dreaming of the hot, humid days of summer, to remind you that every season has its dark side.  When the sun is beating down on us and moisture in the air suppresses our every movement, we will fall prey to a ubiquitous pest that everyone recognizes: the mosquito.  Last year’s wet spring left plenty of standing water for breeding, and the resulting swarms were, in some places, intolerable.  But why do these insects behave the way they do?  How do they find us?  Why do they require our blood?

First came the scouts who felt our sweat in the air
and understood our need to make a sacrifice.  
 
We were so large and burdened with all we had carried
our blood too rich for our own good.  
 

Alison Hawthorne Deming’s poem, “Mosquitoes,” examines the interaction between mosquitoes and humans in a slightly different viewpoint than we are used to.  Most often, humans view mosquitoes as pests, disease-bearing annoyances that inhibit our enjoyment of the outdoors in summer.  Instead, the speaker in this poem views us as a sacrifice, burdened with rich blood ripe for the taking.

There are over 2,700 species of mosquitoes in the world, and all of them require water to breed.  Most eggs overwinter and hatch into larvae in the spring.  Larvae eventually grow into pupae, which after one to four days form a pupal case, within which they metamorphose into adult mosquitoes.  Their purpose now is to mate and feed.

Female mosquitoes are the attackers.  (Males live only a few days after mating, surviving on plant nectar.)  Protein obtained from ingesting blood aides the female in development of eggs.  The mosquito requires a blood meal each time she lays eggs, and can live anywhere from days to weeks, repeating the process of feeding and laying eggs many times.  The eggs hatch or overwinter; the cycle resumes.

Then came the throng encircling our heads like acoustic haloes
droning with the me-me-me of appetite.
 

Several factors have been shown to attract mosquitoes, including: perspiration, heat, light, body odor, lactic acid, and carbon dioxide.  When a female lands on a likely victim, she sucks blood with her proboscis, or feeding apparatus.  There are actually six mouthparts contained in the female’s needle-like proboscis.  The outer sheath is the labium, which bends back to allow the two pointed mandibles and two serrated maxillae to penetrate the skin.  Mosquito bites are generally not very painful because the jagged shape of the maxillae results in a low surface area and a minimum of contact with nerves in the skin.  On the basis of this finding, a Japanese scientist has recently designed a nearly-painless hypodermic needle modeled after a mosquito’s maxilla.

Once the maxillae and mandibles have entered the skin, the mosquito pumps her own saliva into the wound through a hypopharynx, while the tubular labrum allows her to suck blood into her own abdomen.  The saliva contains an anticoagulant, ensuring that blood flow is continuous through the meal.  Itching after a bite is due to our natural immune response to the mosquito’s saliva.  Even after the swollen wheal disappears, the itch remains until your body has broken down the proteins in the saliva.

We understood their female ardor to breed and how little
they had to go on considering the protein required to make
 
their million-fold eggs.  Vibrant, available, and hot,
we gave our flesh in selfless service to their future.  
 

So think of this as you complain about winter.  Remember that summer is coming, and with it, the mosquitoes.  Prepare yourself as a sacrifice.

REFERENCES:

Coxworth, Ben.  04.04.2011.  “Mosquito inspires near-painless hypodermic needle.”  Gizmag.com

Darsie, RF, Jr. and RA Ward.  1981.  Identification and Geographical Distribution of Mosquitoes of North America, north of Mexico.  Fresno, CA: American Mosquito Control Association.

Freudenrich, Craig.  “How Mosquitos Work.”  Howstuffworks.com

“Mosquito Biology.”  Alameda County Mosquito Abatement.  Link. 

“Mosquitoes.”  Alison Hawthorne Deming.  Read it here.

Sutherland, DJ.  2013.  “Mosquitos in Your Life.”  Rutgers School of Environmental and Biological Sciences: Department of Entomology page.  Link. 

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Alive beyond compare.

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“…the heart, exposed exactly for what it is: homelier
than we’d like to imagine.  And alive beyond compare.  
Here, the heart is the heart, and isn’t
a fist or a flower or a smooth-running engine
and especially not one of those ragged valentines
someone’s cut out, initialed, shot full of cartoon arrows:
the adolescent voodoo of desire.  Here, nothing’s colored
that impossibly red.”  
 

In honor of the holiday, I’d like to consider the human heart.  No, not the one usually found in poetry, but the one actually inside of you; the one functioning to carry blood throughout your body, the one transporting oxygen and nutrients and chemicals to every extremity.  David Clewell’s poem “Not to Mention Love: A Heart for Patricia,” is, as the title implies, a love poem written (almost) without the word “love”.  Clewell has tried to

“keep the heart in its proper place for once.  It’s not
in my mouth or on my sleeve  or winging its way lightheartedly 
in circles over my head.  It’s more or less right
where it belongs inside of me, no small thing.”  
 

So, dispensing with hyperbole and flowery romantic language, what we have left is the heart itself.  Put most simply, the heart is just a muscular pump.  But what is its function?  And how does it work?

Inside your heart are four chambers (fun fact: while mammals have four chambers, reptiles and amphibians have three, and fishes, without the need to breathe air, have only two).  The top two are the left atrium and right atrium (plural: atria), and the lower two are the left and right ventricles.  (The “left” and “right” designation always refers to the animal/person whose heart it is: so if a surgeon was looking down a patient, the left ventricle would be on the patient’s left).  Each chamber bears a one-way valve so that when the chamber is contracting, blood can come in, but when the muscles relax, the valve is shut.

The heart works with a two-stage contraction (the contraction phase is called “systole”).  In the first stage, the right and left atria contract simultaneously, pumping blood through their associated valves into the right and left ventricles.  In the second stage of contraction, the right and left ventricles contract simultaneously to push blood out of the heart.  This two-stage process is why you hear a heartbeat as two sounds “lub-DUB”–that’s the sound of your heart valves closing.  After the contraction, the heart muscle relaxes, a phase called “diastole.”  As Clewell writes,

“There’s nothing cute about it.  The heart 
is the heart, chamber after chamber.  Ventricular.  Uncooked.  
In all its sanguine glory.  I couldn’t make up a thing
like that.  The heart’s perfected its daily making do, the sucking
and pumping, its mindless work: sustaining a blood supply
that’s got to go around a lifetime.”  
 

(This last point is not exactly true.  Blood is, in fact, produced in the bone marrow).  In their contractions, the right and left sides of the heart fulfill different functions.  Blood returning from the body is oxygen-poor and enters the right side of the heart (atrium to ventricle).  The right ventricle sends this blood out to the lungs to be oxygenated (and to release carbon dioxide).  This blood then returns to the left side of the heart (atrium to ventricle again) where the much-larger left ventricle pumps oxygenated blood out to the entire body.

But it’s Valentine’s Day!  What about love?

What we call “love” is a combination of emotional attachment and brain chemicals.  Though we may seem to feel things in our “heart”, the heart really has only one thing to do with love: it acts to circulate the aforementioned brain chemicals (dopamine, serotonin, and oxytocin) in the blood out to the body and all the rest of the organs, where they can have the physiological effects that make us feel love.  Does this mean love is all in our heads?  Not at all.  It’s everywhere inside of us, thanks to our powerful hearts.

“Sure, there’s a brain somewhere, another planet,
just seconds or light-years away, and maybe some far-flung
intelligence madly signalling for all it’s worth–
but the heart wouldn’t know about that.  It has its own
evidence to go on.  What’s convincing to the heart
is only the heart.  It doesn’t have the luxury of stopping
to weigh, to reconsider, to fold and unfold the raw data of the world
until it’s creased beyond recognition.  Some days it can’t distinguish 
a single sad note from a chorus of exhilaration, but still
the heart has its one answer down to a science: yes.  Over
and over, the iambic uh-huh.  Whatever it takes, some kind of nerve
or unlikely grace: the heart never knows what to think.”
 

REFERENCES:

Bianco, Carl.  1999.  “How Your Heart Works.”  HowStuffWorks.com.  Link.

“Biological basis of love,” Wikipedia.  Link.

Boston Scientific.  2009.  “Heart Valves.”  Link.  (Check out the cool animations on this site as well!)

“Not to Mention Love: A Heart for Patricia,” by David Clewell.  Read it here.

Wilson, Sue.  2002.  “Red Gold: the Epic Story of Blood.”  pbs.org.  Link.