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introductionstatpearls· Introduction· item NBK482372

The heart becomes the first functional organ in the human embryo. By the end of the fourth week of development, the heart can beat spontaneously. Development of the atrioventricular (AV) septum begins in the third week. Failure of proper development of the atrioventricular septum can result in abnormalities that affect the normal physiology of the heart. These defects can range in severity.[1][2][3]