Hannah is awesome. She may think I am not as I found her paper for her science teacher still open on the computer and loved it so much (it really shows her personality, doesn't it?) that I'm posting it. Hannah, my vegetarian, writes papers instead of dissecting things during labs. I'm guessing this is her latest paper for the latest "I'm not dissecting that" lab. Sadly, her visual aids (drawing of the heart) did not copy and paste, so whenever there is a , that means you need to imagine an illustrated heart or two.
Hannah Perazzo
Mr. Sluyter
Anatomy and Physiology
27 Mar 2013
For the Sake of Sheep Everywhere
“VEGETARIAN: Native American for poor hunter.”
So you might be squeamish. Maybe care for animals. The kind of person who faints at the sight of blood. Or maybe it’s because you enjoyed my last report so very much that you wanted to read another one of my intellectual and insightful reports. Anyway you got here, I hope that you’re ready to learn tons and tons (not literally; this will only be about four pages) about the anatomy of our ever-so functioning (we hope) heart.
Alas, no quote from our home boy Johnny Depp, but we do have some words from H. Jackson Brown, Jr. He said, “Sometimes the heart sees what is invisible to the eye.” Now I’m sure that this man had a great personality and led a normal life and ate ice cream. But misleading the youth of this world is not a very kind thing to do. As we expand our knowledge on heart anatomy, we will be able to pick apart H-Dawg Jackie’s words to shreds.
To start on our wonderful adventure, we will do as Jordan Pruitt is and we will start from the outside looking in. The outside of the heart is probably really gross looking in real life. But that’s the reason we’re all reading this report, so we don’t have to look at a real one. So for the sake of this, we will refer to our hearts as Play-Dough. The muscular walls of our Play-Dough hearts is composed of three layers.
If we start like an onion (or an ogre) the outermost layer is the epicardium. It’s pretty much just connective tissues and fat. Not super exciting, but pretty important. Right underneath that is the bulk of the heart’s walls called the myocardium. The myocardium has the responsibility of contracting and relaxing the heart. Namely the ventricles and atria. It is composed primarily of cardiomyocytes. Cardiomyocytes are pretty big cells (you know, for a cell) that make up 80% of the heart volume. Each cell physically contracts to shorten the heart muscle. Okay, now take a breath. Only one more layer to read about (more or less). So maybe now would be a good time to grab some Chex Mix to help you stay awake. So, the innermost layer (assuming you are back with your Chex Mix) is named the endocardium. Nobody’s quite sure where these names come from… But the endocardium is actually pretty awesome because it’s a smooth membrane that lines the chambers of the hearts and their valves too! [One of the things I said in that last sentence was no a true statement. Try to find it.] (Thinkquest).
But wait! To make sure you don’t end up with internal bleeding after rough roller coasters or intense trampoline sessions, we have the pericardium! “What is the pericardium?” you’re [not actually] asking me?? Well children, gather around and you might get to hear a story about how a pericardium is a double-walled sac in which the heart hangs out. It has within it a pericardium fluid that is like a shock absorber for your little Play-Dough heart. The outermost fibrous pericardium and the inner serous pericardium are the two layers, and they make up the pericardial sac. Yup, it’s “peri” fun.
Just had to leave off that paragraph with a good pun. Everybody loves puns, just like everybody loves the heart. Especially the right side! Now the right side consists of things that are notably from this side, most of the time because it states what side it’s on with it’s name. There’s the superior vena cava, right pulmonary artery, right atrium, right pulmonary veins, fossa ovalis, right atrioventricular valve (tricuspid valve), right ventricle, chordae tendineae, and the inferior vena cava. Don’t those sound awesome! Who know that so much awesomeness is thriving in your body?!
Okay, well the superior vena cava and the inferior vena cava have the mighty job of receiving the oxygen-poor blood from the veins in your awesome body and it pumps it out through the pulmonary trunk. It sort of looks like one of those fat straws that you drink really thick smoothies out of. Not saying that I want to drink your blood like a thick smoothie. Just saying. Now, inferior to the superior vena cava is the right pulmonary artery. Yes, it did say right. Probably insinuating that there’s a left somewhere, but calm down tiger! Don’t get too ahead of yourself. This artery is a split off of the superior vena cava. The superior vena cava takes blood to the right atrium where it gets squeezed like toothpaste up through the right pulmonary artery. The right pulmonary artery take the blood for a car trip to the lungs, picks up some oxygen (with a side of large French fries, of course) and pays with carbon dioxide. This is just a drive-through though, so it is quickly removed by being drained out of your lungs and is returned to the left side of our Play-Dough hearts by way of the pulmonary veins. And it’s oxygen-rich blood and carbon dioxide-poor blood. Take a wild guess on what that now means! …. My guess is that if you have to read this paper to learn, you probably guessed the wrong thing. But have no fear! The answers are here! From the pulmonary veins, blood is taken to the LEFT atrium. Then, the left atrium is contracted to push all that oxygen-rich blood through the left atrioventricular valve (also known as the bicuspid valve). This bicuspid valve takes the blood into the left ventricular which is, in turn, compressed through the aoritic semilunar valve. And that’s pretty much how your heart does what it does. You’re welcome.

Isn’t that picture just so super duper helpful?! I just think it’s my favorite picture!
Now. Let’s go over this whole cardiac cycle with the squeezing and the filling and the letting out. “In a healthy heart, the atria contract simultaneously. Then, as they start to relax, contraction of the ventricles begins. Systole and diastole mean heart contraction and relaxation, respectively. Since most of the pumping work is done by the ventricles, these terms always refer to the contraction and relaxation of the ventricles unless otherwise stated” (Essentials 357). So let’s go over this slowly. Let’s say that our left and right atrium of our Play-Dough hearts are both filled with blood at this current time (because we’re healthy people who only enjoy Chex Mix on occasions). With our atriums full of blood, our body starts saying, “You know? I want to stay alive. I don’t know what about life it is, but I kind of like it.” So in response to your body’s urgent plea, the atriums decide it’s time for some fancy atrial contraction and all the blood ends up in the left and right ventricular. Now we are in the ventricular systole stage (meaning that the atria is in diastole; yay for relaxing!). After filling and contracting, the valves open up to cause the ventricular ejection phase. At the end of all this hard work, the heart takes a second for early diastole where it’s is isovolumetric relaxation. This is the “….” in your heart beat. Don’t understand my strange definition? It’s the “….” when you’re listening to your heart beat (or watching it on a fancy monitor) and your heart sings to you, “Bum-bum …. Bum-bum …. Bum-bum…. Bum-bum….” and so on and so forth until you’re dead.

You’re welcome.
Well, I hope you have a better understanding of the cardiovascular heart and my love for Johnny Depp. And I hope you’ve been able to see why our gangster friend, H-Dawg Jackie was so wrong. Do you understand why? Well we’ve been through this whole heart and not once did we notice anything about a pair of eyes or ESP so therefore, he was dead wrong. “Sometimes the heart sees what is invisible to the eye”? No. I don’t think so. I know for a fact that the eyes can see way more than our little hearts can every hope to see.
Works Cited (not in MLA format; because of laziness)
Think quest - http://library.thinkquest.org/C003758/Structure/walls.htm
Essentials - Essentials of Human Anatomy & Physiology: 8th ed.
No comments:
Post a Comment