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| 31. | cardiogenic area | area near the head of the embryo where the heart begins to develop 18-19 days after fertilization |
| 32. | cardiogenic cords | two strands of tissue that form within the cardiogenic area |
| 33. | cardiomyocyte | muscle cell of the heart |
| 34. | chordae tendineae | string-like extensions of tough connective tissue that extend from the flaps of the atrioventricular valves to the papillary muscles |
| 35. | circumflex artery | branch of the left coronary artery that follows coronary sulcus |
| 36. | coronary arteries | branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system |
| 37. | coronary sinus | large, thin-walled vein on the posterior surface of the heart that lies within the atrioventricular sulcus and drains the heart myocardium directly into the right atrium |
| 38. | coronary sulcus | sulcus that marks the boundary between the atria and ventricles |
| 39. | coronary veins | vessels that drain the heart and generally parallel the large surface arteries |
| 40. | diastole | period of time when the heart muscle is relaxed and the chambers fill with blood |
| 41. | ejection fraction | portion of the blood that is pumped or ejected from the heart with each contraction; mathematically represented by SV divided by EDV |
| 42. | electrocardiogram | (ECG) surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function; also abbreviated as EKG |
| 43. | end diastolic volume | (EDV) (also, preload) the amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction |
| 44. | end systolic volume | (ESV) amount of blood remaining in each ventricle following systole |
| 45. | endocardial tubes | stage in which lumens form within the expanding cardiogenic cords, forming hollow structures |
| 46. | endocardium | innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium |
| 47. | endothelium | layer of smooth, simple squamous epithelium that lines the endocardium and blood vessels |
| 48. | epicardial coronary arteries | surface arteries of the heart that generally follow the sulci |
| 49. | epicardium | innermost layer of the serous pericardium and the outermost layer of the heart wall Frank-Starling mechanism relationship between ventricular stretch and contraction in which the force of heart contraction is directly proportional to the initial length of the muscle fiber |
| 50. | filling time | duration of ventricular diastole during which filling occurs |
| 51. | foramen ovale | opening in the fetal heart that allows blood to flow directly from the right atrium to the left atrium, bypassing the fetal pulmonary circuit |
| 52. | fossa ovalis | oval-shaped depression in the interatrial septum that marks the former location of the foramen ovale |
| 53. | great cardiac vein | vessel that follows the interventricular sulcus on the anterior surface of the heart and flows along the coronary sulcus into the coronary sinus on the posterior surface; parallels the anterior interventricular artery and drains the areas supplied by this vessel |
| 54. | heart block | interruption in the normal conduction pathway |
| 55. | heart bulge | prominent feature on the anterior surface of the heart, reflecting early cardiac development |
| 56. | heart rate | (HR) number of times the heart contracts (beats) per minute |
| 57. | heart sounds | sounds heard via auscultation with a stethoscope of the closing of the atrioventricular valves ("lub") and semilunar valves ("dub") |
| 58. | hypertrophic cardiomyopathy | pathological enlargement of the heart, generally for no known reason |
| 59. | inferior vena cava | large systemic vein that returns blood to the heart from the inferior portion of the body |
| 60. | interatrial band | (also, Bachmann's bundle) group of specialized conducting cells that transmit the impulse directly from the SA node in the right atrium to the left atrium |
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