Question

1. Describe heart development, starting at neurula stage. Relate genetics associated with congenital heart defects to this process

Answer 1

• Early development of heart begins at a prominent heart bulge at anterior surface of the embryo.
• The heart forms an embryonic tissue called mesoderm around 18-19 days after fertilization .It begins to develop from near the head of embryo in a region is known as cardiogenic area.
• These cardiogenic area develop into two strands called cardiogenic cords and later into endocardial tube.
• These two tube fuse together to form a single primitive heart tube.From head to tail it develop as truncus arteriosus , bulbus cordis , primitive ventricle, primitive atrium, and the sinus venosus.
• Five region of primitive heart tube develop into recognizabe structures in a fully developed heart.Truncus arteriosus divide into ascending aorta and pulmonary trunk.
• Bulbis cordis develop into right ventricle, primitive ventricle forms the left ventricle .The primitive atrium becomes anterior portion of left and right atria and auricles.
• The sinus venosus develops into posterior portion of right atrium , SA node and coronary sinus.
• Chromosomal aneuploidy , is the first recognized cause for congenital heart defect (CHD) and continous major pathogensis today.CHD occurs 40-50% of trisomy 21 , 20-50% of turners syndrome , and in almost all cases of both trisomy 13 and trisomy 18.