4. embryology of heart Flashcards
stages of heart formation
linear heart tube formation
formation of cardiac loop
heart septation
cavitation of ventricle, formation of valves and great vessels
4 chambered heart
where is the inflow tract?
sinus venosus
How does the cardiac loop form?
As the ventricles and bulbus cordis of the heart grow faster than other regions, the heart bends in a rightward direction. This leads to the atrium and sinus venosus, which were initially caudal (below) to the ventricle, moving cranially and dorsally.
cardiac looping after 28 days
what are endocardial cushions?
localised swellings in the outflow region and atrioventricular canal.
what happens to endocardial cushions?
enlarge and protrude into lumen of heart
become cellularised-> activated cells, migrated into endocardial cushions
septa fuses with cushions
endocardial cushions form cardiac valves
septation of primordial atrium
4 weeks
Perforations form in septum primum, the developing foramen secundum
septation of primordial atrium
5-6 weeks
foramen secondum formed, foramen primum closes
formation of the great arteries
- truncal and bulbar ridges/ cushions are continuous but positioning shows that they are spiralling around outflow region of heart
- Division of the truncus arteriosus and bulbus cordis into the aorta and pulmonary trunk, occurs by the formation of the aorticopulmonary septum
- the aorticopulomnary septum spirals, so pulmonary trunk twists around ascending aorta
how do semi lunar valves form in aorta and pulmonary trunk
When division of the truncus arteriosus is nearly complete, swellings begin to form near the entrance to the newly formed aorta and pulmonary trunk (outflow region of the heart), from endocardial cushions.
These swellings are the primordial aortic and pulmonary valves, and will ultimately form the mature semilunar valves.
formation of SVC and IVC
Are derived from primordial veins which undergo a series of changes during development, leading to their remodelling and incorporation into these new vessels.
formation of pulmonary veins
Most of the smooth wall of the LA is derived from the primordial pulmonary vein and its branches. As the atrium expands, more of the primordial pulmonary vein is incorporated, until ultimately 4 veins are present.
Oxygenated blood from placenta
Enters in right atrium
Blood shunted straight to left atrium to left ventricle then around body
Some mixing of blood from blood returning of embryo and lungs
After first breath;
Three shunts close,
how does foramen ovale close in postnatal circulation
- Lungs expand
- decreased Resistance to blood flow
- Pressure in RA < LA
- Blood stops flowing through foramen ovale
three shunts that close
foramen ovale
ductus arteriosus constricts to form ligamentum arteriosum
ductus venosus constricts to form ligamentum venosus in the liver
5 congenital heart defects
atrial septal defects
ventricular septal defects
patent ductus arteriosus
patent truncus arteriosus
tetraology of fallot
atrial septal defect
hole in heart
patent foramen ovale
usually small and of no significance if isolated
- The most clinically significant type is ostium secundum ASD
more common in females
Enlarged RA, RV, PA
ventricular septal defect
Most common CHD
- More common in males
- Usually involves membranous part of interventricular septum failing to develop normally
