NEURO 661 Lecture Notes - Lecture 10: Sinus Venosus, Septum Primum, Great Vessels
Document Summary
Learning objectives: explain how postnatal heart structures develop from the primitive heart tube, describe septal defects that may occur during development. Development of the heart commences in the third week, when the embryo becomes too large to receive its nutrients through diffusion alone. The steps involved in heart development are complex, because the heart must begin working before its development is complete ( gure 19. 27). Development of the heart. the heart develops from mesoderm. The foramen ovale is a passageway that detours blood away from the pulmonary circulation into the systemic circulation prior to birth. By day 19 (middle of week 3), two heart tubes (endocardial tubes) form from mesoderm in the embryo. 21, these paired tubes fuse, forming a single primitive heart tube ( gure 19. 27a). By day 22, the heart begins to beat, and later in the fourth week, this single heart tube bends and folds upon itself to form the external heart shape ( gure 19. 27b).
