Overview
- Heart development
- 5 dilatations along primitive heart tube forms into adult heart structures
- dextral looping of the primitive heart aligns the heart chambers and structures
- septum and valves develop which allow for separation of the venous and arterial circulatory pathways
- heart begins beating during week 4
- can be detected by transvaginal ultrasound by week 6
Embryonic structures
| Embryonic structure | Adult structure |
| Truncus arteriosus | Ascending aortaPulmonary trunk |
| Bulbus cordis | Smooth part of left and right ventricle |
| Primitive ventricle | Trabeculated part of left and right ventricle |
| Primitive atria | Trabeculated part of left and right atrium |
| Sinus venosus | Coronary sinusSmooth part of right atrium |
Right common and right anterior cardinal vein
- SVC
- Truncus arteriosus
- neural crest cells migrate from hindbrain to aorticopulmonary (AP) trunk
- cells invade truncal and bulbar ridges
- the ridges then twist, spiral, and fuse to form the AP septum dividing the AP trunk into the ascending aorta and pulmonary trunk
- neural crest cells migrate from hindbrain to aorticopulmonary (AP) trunk
- Persistent truncus arteriosus
- partial development of AP septum resulting in mixing of oxygenated and deoxygenated blood leading to cyanosis
- Transposition of great vessels (transposition of great arteries)
- ridges do not spiral as they develop resulting in two separate circulatory pathways
- blood never gets oxygenated which will result in neonatal death, unless there is a shunt between the two pathways
- VSD, patent foramen ovale, or PDA
- Tetralogy of Fallot
- skewed development of AP septum resulting in
- Pulmonary stenosis
- Right ventricular hypertrophy
- Overriding aorta
- VEntricular septal defect
- skewed development of AP septum resulting in
- cyanosis but severity depends on degree of pulmonary stenosis
Interventricular septum development
- Muscular ventricular septum
- forms from the floor of the primitive ventricle
- opening between muscular ventricular septum and fused AV cushions is called interventricular foramen
- AP septum then fuses with muscular ventricular septum to form the membranous interventricular septum
- Common ventricle
- muscular and membranous interventricular septum do not form
- Membranous septal defect
- failure of the membranous interventricular septum to form properly
- blood flows from left to right due to higher pressure in systemic circulatory system
- as a result pulmonary hypertension develops
- the lumen of pulmonary arteries and arterioles narrow due to proliferation of the tunica media and intima
- pulmonary resistance then becomes greater than systemic reversing the flow of blood across the opening
- the resulting condition is called Eisenmenger complex
Interatrial septum development
- Septum primum
- grows downward from the superior part of the primitive atrium
- as the septum primum nears the atrioventricular cushions, new openings form at the center creating the foramen secundum
- foramen secundum allows for shunting of the blood from right to left
- Septum secundum
- grows downward and covers the foramen secundum leaving an opening inferiorly
- superior portion of septum primum degenerates
- inferior portion of septum primum and septum secundum form the foramen ovale
- foramen ovale remains open until birth
- at birth, right atrial pressure decreases and left aftrial pressures increases due to increased pulmonary blood flow into left atrium resting in the closure of the foramen ovale
- Patent foramen ovale
- foramen ovale does not close due to excessive resorption of septum primum, secundum, or both