Cardiovascular System Development

Formation of heart - day seventeen to nineteen

Originates from sphlanchnic mesoderm layer, two longitudinal cell clusters form at cranial part of embryo and fuse to become paired endocardial heart cells

Formation of heart - day eighteen to twenty two

Both endocardial tubes fuse to form primitive heart tube - will move towards future thoracic cage due to cranio caudal folding

Formation of heart - day twenty three to twenty nine

Heart primitive tube folds to remodel heart, partitioning of heart occurs with formation of septum primum and then septum secundum in atria - forms two atria chambers connected by foramen ovale, ventricular septum appears and separates ventricles

Foramen ovale 

Opening in septum between atria of heart that closes at birth

Ductus arteriosus

Channel or connection between pulmonary artery and aorta in foetus, bypasses lungs to distribute oxygen received through placenta from mothers blood, normally closes at birth and lungs inflate, separates pulmonary and systemic circulations, causes hypoxia if does not close properly

Umbilical vein/artery

Umbilical vein carries oxygenated blood from placenta to foetus, umbilical arteries carry deoxygenated blood from foetus to placenta

Ductus venosus

Vitelline blood vessel lying within liver that connects portal and umbilical veins to inferior vena cava, acts to protect foetus from placental over circulation, shunt functionally closes after birth

Pressures at birth

Increase of blood pressure on left side as a result of opening pulmonary circulation, pressure forces increase = fusion of septum primum and secundum and closing of foramen ovale,