Embryology - CVS Flashcards
What are the stages of heart development?
Formation of blood vessels.
Formation of pericardium.
Formation and looping of heart tube.
Formation of atrioventricular canals.
Septation of primitive atria and ventricles.
Formation of the heart conducting system.
How does the CVS develop?
First major system to develop (4 weeks).
A rapidly growing embryo will not be satisfied by nutrition by diffusion.
What happens in week 3 in the CVS?
Blood vessels (‘angioblastic islands’) first appear in the yolk sac, allantois, connecting stalk, and chorion - this is called the cardiogenic field.
How is the primordial CVS formed?
Blood vessels in the lateral plate splanchnic mesoderm form two heart tubes. The heart tubes fuse and joins blood vessels in other areas.
How is the pericardium formed?
Cranial folding of the embryo causes the heart tube to lie dorsal to the pericardial cavity.
Somatic mesoderm - parietal, serous and fibrous pericardium.
Splanchnic mesoderm - visceral serous pericardium.
Intra-embryonic coelom - pericardial cavity.
How is the heart tube formed?
The heart starts to bulge and differentiate into arterial (cranial) and venous (caudal) ends.
Top to bottom - TA, BC, PV, PA, SV.
The primitive tube invaginates the pericardium, and becomes too large.
How does the heart tube loop?
It folds and loops into a bulboventricular loop.
The bulbus cordis and ventricle enlarge and loop on the right.
Ventricle - left and inferior.
Atria - superoposterior.
What is dextrocardia?
The most frequent positional abnormality of the heart. The heart tube loops to the left side, and the ventricles lie facing the right.
How are the atrioventricular canals formed?
The endocardial cushion growth separates the RA and RV from the LA and LV.
How is the foramen ovale formed?
A septum primum forms.
The ostium secundum begins to form by apoptosis as part of the septum primum.
An ostium primum forms and closes, as the septum primum meets the endocardial cushions.
What is the function of the foramen ovale?
Most blood passes from the RA to the LA, through the one-way shunt (non-functioning lungs).
What happens to the foramen ovale after birth?
It normally closes, from increased pressure in the LA due to increased pulmonary circulation.
The septum primum fuses with the septum secundum.
The fossa ovalis (a depression in the interatrial septum) is a remnant in the adult heart.
What is PFO?
When the foramen ovale fails to close.
Patent Foramen Ovale occurs.
A common form of congenital Atrial Septal Defect (ASD).
What structures are formed in the septation of the primitive ventricles?
A muscular ventricular septum forms.
The opening is called the interventricular foramen.
The aorticopulmonary septum divides bulbis cordis and truncus arteriosus into aorta and pulmonary trunk.
How is the interventricular foramen closed?
The bottom of the spiral aorticopulmonary septum fuses with the muscular ventricular septum and endocardial cushions to form the membranous interventricular septum, closing the interventricular foramen.
