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.”
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.