Embryology of the Cardiovascular System Flashcards
What is the definition of the cardiovascular field and vasculogenic?
Cardiovascular field: The embryonic region giving rise to the heart and blood vessels.
Vasculogenic: The formation of new blood vessels from mesodermal precursors called angioblasts.
How does the heart tube form, and what are its parts?
Formed from splanchnic mesoderm in the cardiogenic area.
The heart tube consists of:
- Truncus arteriosus → Forms great arteries
- Bulbus cordis → Forms part of ventricles
- Primitive ventricle → Forms left ventricle
- Primitive atrium → Forms auricles and atria
- Sinus venosus → Forms part of right atrium and veins
What is the bulboventricular loop, and what is dextrocardia?
The heart tube folds rightward to form an S-shape (bulboventricular loop).
Dextrocardia: A condition where the heart folds leftward, resulting in a mirror-image heart position.
Whats the difference between dextrocardia and dextroposition?
Dextroposition describes a heart on the right with an apex to the left, secondary to extracardiac causes (right lung hypoplasia, pneumonectomy or diaphragmatic hernia). In contrast, dextrocardia results from cardiac chamber disarrangement
How does the septum form in the atria and ventricles?
Atria:
Septum primum grows down, leaving the foramen primum.
Foramen secundum forms in septum primum before it fuses with the septum secundum.
The gap in the septum secundum becomes the foramen ovale (closes at birth).
Ventricles:
Muscular septum grows upward.
Membranous septum forms from endocardial cushions and bulbar ridges.
How do the AV canals and cardiac valves develop?
Endocardial cushions grow and separate the single AV canal into right (tricuspid) and left (mitral) AV canals.
Cardiac valves form from mesenchymal proliferation in the AV canals and outflow tracts.
How does the specialized conducting system develop?
The SA node develops from the right sinus venosus.
The AV node and bundle of His arise from the AV canal and atrial myocardium.
What are the aortic arch derivatives and their anomalies?
1st arch → Maxillary artery
2nd arch → Stapedial artery
3rd arch → Common & internal carotid arteries
4th arch → Aortic arch (left), subclavian artery (right)
6th arch → Pulmonary arteries, ductus arteriosus
Anomalies:
Coarctation of the aorta (narrowing)
Double aortic arch
Right aortic arch (instead of left)
How does the venous system develop?
Three major embryonic veins:
Vitelline veins → Portal system and liver veins
Umbilical veins → Carry oxygenated blood from placenta
Cardinal veins → Form systemic veins (SVC, IVC)
How does the lymphatic system develop?
Develops from lymph sacs (jugular, retroperitoneal, cisterna chyli).
Forms major lymphatic vessels like thoracic duct.
What is foetal circulation, and what changes occur at birth?
Foetal circulation: Blood bypasses lungs via:
Ductus arteriosus (aorta ↔ pulmonary artery)
Foramen ovale (right atrium ↔ left atrium)
At birth:
Lungs expand → Ductus arteriosus closes
Foramen ovale closes → Becomes fossa ovalis
What is the embryological basis of atrial septal defect (ASD)?
Failure of septum primum and septum secundum to close properly.
Leads to persistent foramen ovale, allowing left-to-right shunting of blood.
What causes ventricular septal defects (VSDs)?
Failure of membranous septum to close, leading to left-to-right shunting of blood.
Most common congenital heart defecr
What is patent ductus arteriosus (PDA)?
Failure of the ductus arteriosus to close after birth.
Causes continuous “machine-like” murmur and left-to-right shunting.
What is coarctation of the aorta?
Narrowing of the aortic arch, leading to hypertension in the upper body and weak pulses in lower limbs.
What is Tetralogy of Fallot, and what are its four features?
Pulmonary stenosis
Right ventricular hypertrophy
Overriding aorta
Ventricular septal defect (VSD)
Causes cyanosis due to right-to-left shunting.
