Embryology 2 - Development of the CVS Flashcards
What is the atrioventricular canal?
A constriction between the atrium and ventricle, making the first division between the two
What is the first step in septation?
Development of endocardial cushions on dorsal and ventral sides of atrioventricular canal
What do the endocardial cushions do?
Grow towards each other to divide the heart into right and left channels
What is the septum primum?
Grows down towards the fused endocardial cushions
What is the ostium primum?
The hole present before the septum primum fuses with the endocardial cushions
What is the ostium secundum?
A hole formed in the septum primum by apoptosis before the ostium primum closes
What is the septum secundum?
A crescent shapes second septum
What is the foramen ovale?
A hole in the septum secundum
What is the fossa ovalis?
The adult remnant of the foramen ovale
What are the 2 components of the ventricular septum?
Muscular and membranous
Which portion of the ventricular septum froms the majority?
Muscular
How does the muscular portion of the septum grow?
Upwards towards the endocardial cushions
What is the primary interventricular foramen?
The hole at the top of the muscular portion of the ventricular septum
What is the role of the membranous portion of the septum?
Fills the gap to close the primary interventricular foramen
What is the membranous portion derived from?
The spiral septum that grows to separate the truncus arteriosus into the outflow vessels
Why are the lungs mostly bypassed in foetal circulation?
Non functional
If they receive a lot of blood during development, they will be damaged
How does the foetus receive oxygenated blood?
Via the placenta and umbilical vein - bypasses the lungs and returns to the placenta via the umbilical arteries
When does foetal circulation change to adult circulation?
Immediately
Which shunts are there in the foetal circulation?
Ductus venosus
Foramen ovale
Ductus arteriosus
What is the role of the ductus venosus?
Allows oxygenated blood to pass from the placenta into the inferior vena cava via the umbilical vein
What is the role of the foramen ovale?
Allows the blood to pass from the right atrium to the left atrium
What is the role of the ductus arteriosus?
Allows blood to pass from the pulmonary trunk to the aorta - bypasses the lungs
What is the process of shunts closing on the baby’s first breath?
- Huge decrease in pressure in the lungs.
- More blood enters lungs.
- More blood returns to left atrium.
- Pressure in left atrium > right atrium.
- Foramen ovale closes.
- Ductus arteriosus contracts.
- Placental support is removed so ductus venosus closes.
What is the adult form of the foramen ovale?
Fossa ovalis
What is the adult form of the ductus arteriosus?
Ligamentum arteriosum
What is the adult form of the ductus venosus?
Ligamentum venosum
What is the adult form of the umbilical vein?
Ligamentum teres
