this lecture introduces the basic layout of the heart and begins to talk about blood flow dynamics. blood flows in through the inferior and superior vena cava into the right atrium, which uses its pectinate muscles and vestigial auricle to contract and squeeze the blood through the tricuspid valve into the right ventricle. while the tricuspid is open it is stabilized by chordae tendonae, which are tendons that are attached to the papillary muscles, which contract during the valve opening in order to stabilize. when the right ventricle contracts, it goes out of the pulmonary semi-lunar valve, which leads to the pulmonary vein, which leads to the lungs.
the now oxygenated blood comes back through the pulmonary artery into the left atrium, and is then let into the left ventricle via the bicuspid (or mitral) valve. once in the left ventricle, it is squeezed out through the aortic semi lunar valve into the aorta, in order to irrigate all the capillaries of the body.
systole is the expulsion of blood from the heart and diastole is the filling of the heart. the first heart sound comes from systole of the ventricles, where the atrioventricular cusps are shut closed due to the pressure from contraction. diastole is the second heart sound, which is the sound of the semilunar valves closing back up under the retrograde pressure of the column of blood in the aortas, which fill the sinuses behind the cusps of the SLV and shut it.
the coronary artery is the blood supply to the heart muscle itself. the left is split into the anterior descending and the circumflex, and the right is split into the posterior descending and the marginal. coronary bypass is when a piece of thoracic artery (for thick arteries like the anterior descending) or saphenous veins (for thin arteries like the marginal) is grafted in as a shunt to bypass any "occlusion", which is a site of blockage or damage.
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