Since I have learned a lot about how our heart works within my paramedic courses in 2012, I'd like to share some drawings I made during these courses. I labelled them in English in order to broaden my language skills. I really hope you can learn something from it. By the way, it might be a good idea to look at the drawings every once in a while while you're reading. Otherwise it might be a little confusing as there are LOADS of foreign words (of which some of them are explained below).
How the Heart Pumps Blood
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| (c) Sophie Schaffner |
Our heart is a fist-sized muscle situated behind the rib cage and between the lungs. Since it is placed slightly to the left of the sternum (breastbone), the left part of the lungs is a little smaller than the right one. The heart contracts in order to pump oxygen- and nutrient-rich blood to the rest of your body.
The heart is divided into the right pumping system and the left pumping system. The right atrium (blue color) receives oxygen-poor blood from the superior vena cava and pumps it to the right ventricle (also in blue color). Following that, the right ventricle pumps the blood to the lungs through the pulmonary artery. In the lungs, the blood picks up oxygen and gets rid of carbon dioxide. The left atrium (red color), however, receives oxygen-rich blood from the pulmonary veins and pumps it to the left ventricle. Through the aorta, the left ventricle pumps the oxygen-rich blood to the rest of the body. The aorta (Aorta, Hauptschlagader) is the biggest artery and has millions of smaller arteries branching off. By passing through chest and abdomen, the aorta is responsible for "carrying" oxygen-rich blood to all your organs and cells.
Arteries are blood vessels that deliver oxygen-rich blood from the heart to the cells of your body. They are thick-walled and elastic and their smaller branches are called arterioles and capillaries.
Veins are thin-walled blood vessels delivering oxygen-poor blood to the lungs. Have you ever been wondering why blood in the veins of your feet flows upwards, although, locigally, gravity would keep it down below? Well, some veins have venous valves that set the direction where the blood moves. Thank God! Because otherwise all your blood would be stuck in your feet and ... yeah, you can imagine how your feet would look like.
The Cardiac Conduction System
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| (c) Sophie Schaffner |
The cardiac conduction system generates and controls the heart rate. Have a look at the drawing first and search for the sinoatrial node (sinus node). This is where we start: The sinus node is the heart's natural pacemaker. The electrical impulses are generated here. This electrical signal moves from cell to cell down through the heart until it reaches the atrioventricular node (AV node). The AV node somehow slows the electrical current down. By doing so, the node ensures that the two atria (plural of atrium) can fully contract and pump out blood. After passing the AV node, the electrical current "travels" to the ventricels until it reaches the purkinje fibers (special cardiac muscles). These fibers kind of "tell" the cardiac muscles to contract.
Normally, a sinus node produces a heart rate of 60 to 80 per minute. In case the sinus node is not functioning anymore, the AV node takes over, but can only produce a heart rate of 40 to 60. By the way, the heart rate is the pulse you can feel at your wrist. The blood pressure, however, is something completely different and cannot be explained in just one sentence. If time allows, I will write another blog post and tell you what blood pressure actually is about.
Vocabulary
right atrium (rechter Vorhof) = the right upper chamber of the heart that receives blood from the vena cavaleft atrium (linker Vorhof) = the left upper chamber of the heart that receives blood from the pulmonary veins
right ventricle (rechte Herzkammer) = the right lower chamber of the heart that receives blood from the right atrium and pumps the blood into the arteries
left ventricle (linke Herzkammer) = the left lower chamber of the heart that receives blood from the left atrium and pumps blood into the aorta
pulmonary artery (Lungenarterie) = an artery which carries blood from the heart to the lungs
venous valves (Venenklappen) = a structure that prevents blood from flowing backwards and therefore ensures a one-way flow
sinus node (Sinusknoten) = special part of the heart that controls the heart beat and heart rate
av node (AV-Knoten) = a node that receives impulses from the sinoatrial node
electric current (elektrischer Strom) = a flow of electricity
Sources
Sanitätshilfe - "Ausbildung", Auflage Februar 2012, Herausgeber: Österreichisches Rotes Kreuzhttp://flexikon.doccheck.com/de/Herz#Anatomie
http://www.webmd.com/heart-disease/guide/how-heart-works
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Any questions? Feel free to add a comment! :-)
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