Med School Anatomy, Sorta

Given the title of this post, I suspect absolutely no one is going to give it a read. No worries. Except for bleary-eyed med students, I'm probably the only creature in LA right now, at 9:30 pm, who's got the anatomy of the heart and lungs on her mind, and wants to write about it too. So feel free to ditch.

A few days ago I posted a black & white drawing that I really love of a bird atop a pair of lungs and the handwritten words "The Love Between Two Lungs." 

My primary focus was on the bird and the lungs, secondary the dangling heart that I figured must represent "the love between." The artist's positioning of the heart between the lungs struck me as odd. Recently, I chided my friend, alias Larry, about not knowing we each have two lungs. But now I find I have been similarly clueless about where the heart lies inside us. I kinda sorta thought it was somewhere close to the left lung but on the lung's outer side. Where the heart resides exactly I didn't know and didn't even realize I didn't know. 

Whenever Colleen and I talk about the pulmonary artery connecting the right side of the heart to the lungs, I have always assumed that the lungs have a single pulmonary artery only. No, I've just learned. The lungs have two pulmonary arteries, one for each lung. During those discussions, I have also vaguely imagined the heart beating somewhere north of the lungs. Wrong.

For the past few days the image of the bird, the lungs, and strangely positioned heart nagged at me. So I went Googling and found out not only where my heart is but also that it only weighs about 9 ounces. It makes up less than 0.5% of our total body weight.

Voila:

The heart isn't "outside" the lungs, nor is it located on the left of the left lung. Rather, it's almost dead center in between them. I say "almost" because 2/3 of the heart is left of the midline of the body (think sternum or spine) and 1/3 of the heart is on the right. 

How could I have not known this?

The Pledge of Allegiance comes to mind. From kindergarten on, we recited the Pledge of Allegiance at the start of every school day. We each put our right hand on our heart, or what we thought was our heart. Every kid's hand, including mine, was placed somewhere below the left clavicle and to the left of the sternum. As an adult, I somehow came to know that the heart was not located in that upper left quadrant of the torso, though I continued to think it was somewhere in that vicinity, only lower. I never, not once, thought about it's proximity or relationship to the lungs.

(The size of the lungs in this illustration surprised and stunned me. More on that to follow.)

This next, purposely distorted diagram nicely illustrates the fact there there are two pulmonary arteries (in blue):

This last illustration gives us an idea of what pulmonary hypertension and an enlarged right heart look like:

Colleen's pulmonary hypertension--all pulmonary hypertension--affects the left pulmonary artery only because the fibrosis or hardening in her lungs makes pumping blood into them more difficult for the right heart. As a consequence, the pulmonary artery swells under the pressure of blood unable to course through it swiftly and, also, the right heart swells or enlarges as well. The inelastic lungs become somewhat like a dam. Everything behind it backs up.

.....

If you're still reading, did you know that the lungs are as big as these images show them to be? Our lungs take up almost all of our chest space and, along with the heart, sit inside our ribs for protection. 

The size of adult human lungs vary greatly. But the average length is 10 to 14 inches and they weigh an average of 2 to 3 pounds! (Remember that the heart, by contrast, only weighs on average 9 ounces; the size of the heart is only, approximately, the size of a fist.)

.....

Now that Colleen is in full throttle exploring the possibility of a lung transplant, I want to be as un-vague as possible about all aspects. Until now, I had given little thought to the organs of the lungs themselves. If Colleen has lung transplant surgery, the donor lungs will likely be somewhere around 10 inches long. And in order for the surgeon to attach these new lungs into Colleen's body, to make them hers, he (and we're pretty sure it would be a "he") has to work around the heart situated right in the middle of things.

I'm glad to know this.

Yours,
The Professor