First heart beats of embryoBilim
The heart and great vessels form from mesenchymal cells in the cardiogenic area. Paired, longitudinal endothelial-lined channels, or endocardial heart tubes, develop during the third week and fuse to form a primordial heart tube. The tubular heart joins with blood vessels in the embryo, connecting the stalk, chorion, and umbilical vesicle to form a primordial cardiovascular system. By the end of the third week, the blood is circulating, and the heart begins to beat on the 21st or 22nd day.
Sayfa 62
Heavy cigarette smoking is known to cause intrauterine growth restriction and under-weight babies and that the incidence of prematurity increases with the number of cigarettes that are smoked.
Sayfa 505 - e-kitap
Reklam
Because the beginnings of most essential external and internal structures are formed during the fourth to eighth weeks, this is the most critical period of development. Developmental disturbances during this period may give rise to major birth defects.
Sayfa 88 - e-kitap