Intro to the Heart

Position of the Heart

When we approached the heart, it’s good to review and make use of our anatomical terms.

I mean, you know where it is, right? You have placed your hand over your heart for the Pledge of Allegiance in grammar school for many years.

Your heart is anteriorThe front of the body or toward the front when standing in the anatomical position. to your spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae., your trachea, and your esophagusThe muscular tube that transports food from the pharynx to the stomach via peristalsis.. It is posterior to the sternumFlat bone forming the center of the chest; anchor for ribs and clavicles. Appears as a vertical dagg or breastbone that provides it with protection. It’s superiorAbove or toward the upper part of the body. to your diaphragm. For those of you who are unsure, the diaphragm is this big muscle down here. It’s really parachute shaped.

The heart’s also medialToward the midline of the body to each lung. The heart takes more space from the left lung than it does from the right. You can see this here. This is the genesis of why the right lung has three lobes, and the left lung only has two.

At its most inferiorBelow or toward the lower part of the body. border, it comes to a point called the apex.  This is attached here to the diaphragm. The baseA substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻). of the heart is the superior borderTop edge of the scapula; shortest of the three borders. and is also attached to the structures surrounding it.  The portion of the thoracic cavityThe body cavity housing the heart and lungs. that the heart occupies is called the mediastinum.

The Heart Wall

This inset is a little portion of the heart wall of the left ventricle.  If we had to cut into someone’s heart, the scalpel would pass through the layers of the heart wall in this sequence:

The fibrous pericardiumThe membrane surrounding the heart. which secures the heart into the mediastinum. The parietal layer, of the pericardium which is the same as the parietal layers of serous membranesThin tissues that line body cavities and secrete fluid. we’ve seen before. The pericardial cavity is full of fluid to reduce the friction caused as the heart changes shape with every beat. The visceral layer of the pericardium also takes the name epicardium.  It is like a connective tissue stocking that hugs the muscular tissue of the heart. The myocardium is the cardiac muscle tissue of the heart wall responsible for contraction. And finally, the deepest layer of the heart wall, the layer that lines the open chambers is called the endocardium.  The simple squamous cellsThe basic structural and functional units of life. of the endocardium are continuous with the lining of all your blood vessels.  Collectively, we can call the lining of any blood0filled vessel or chamber endotheliumThe innermost layer of blood vessels, composed of simple squamous epithelial cells, which reduces f.

The Pericardial Cavity

The pericardial cavity is like a fluid filled balloon that the heart sits in.  The classic example of a serous membrane like the pericardium is imagining someone pushing their fist into a balloon.  The balloon kind of wraps around your fist with an air filled wrapping.  If this area becomes inflamed or filled with excess fluid, this fluid can prevent the heart from expanding in contraction.  This is called cardiac tamponade.  Because the heart can’t contract and forcibly eject blood, blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. drops.  In response to all this, the heart thinks it can’t pump MORE blood in each contraction. So, it decides to pump faster, hoping that it will work.  Heart rate increases, but it doesn’t matter because the problem is that excess fluid. 

Coronary Vessels

On the outside of the heart are these structures called the coronary vessels. The heart does not get high on its own supply. The blood that’s flowing through the heart does not feed the myocardium. The myocardium is not dipping into that. In factA statement based on direct observation that is repeatedly confirmed., what’s really weird is that the heart feeds itself as though it were a separate organ. Blood comes off the aorta and gets routed to your kidney. Similarly, blood comes off and goes to your heart.

On the outside of the heart are these coronary vessels. Some people call it a coronary circuit. They run through the myocardium, but they really are on the superficialNear the surface of the body. surface of it. These vessels are incredibly tiny. They experience high pressure. Because of this, they can be subjected to blowouts, especially the artery.

Now, when the heart contracts, all of these arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr briefly constrict. Blood stops flowing. Then the heart relaxes, and the arteries open up again. I find it interesting that the heart, as it contracts for a split second, shuts off its own blood supply. The heart gets blood just like any other organ coming off the aorta, but it doesn’t apply for the drainage of it. This coronary sinus right here collects all the blood from the veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge of the coronary circuit. It dumps that blood right into the right atrium.

Myocardial Infarction

Here, it’s a heart attack, right? There’s a little blockage right here. And this myocardium is not being fed glucoseA simple sugar that is the main source of energy for cells. and oxygen, and the muscle tissue starts to die. This is similar to when you sit on your feet. You cut off blood supply. After a while, it starts to tingle. You can’t really contract it. My foot’s asleep. Well, this is when your heart’s asleep, and this is called a myocardial infarction.  If cardiomyocytes die, they will start to release their actin and myosin into circulation.  Remember that actin had that tropomyosin and troponin that made the actin filament?  If you don’t know, now is your chance. Stop this video and go back to the muscle chapter. Review the information.   To detect a heart attack, we might first take blood and look for cardiotroponins.  After that, we might do some imaging of the heart. We want to identify a blocked artery in the cardiac circuit.  We can declog or bypass the blocked artery.  This picture is great. It illustrates how the saphenous vein of the radial artery can be used as a bypass avenue.

Rule of 4

Veins always drain blood and arteries always carry blood away from the heart.  In the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu, which we use to teach about the cardiovascular systemThe organ system that includes the heart and blood vessels, responsible for circulating blood and ox, veins carry deoxygenated blood. Arteries carry oxygenated blood in this circuit.  In the pulmonary circuitThe circulation of blood between the heart and the lungs, where blood is oxygenated., it’s the opposite: arteries carry deoxygenated blood, and veins bring oxygenated blood back to the heart.