Flashcards in Primer 8 - Cardiac Embryology Deck (28):
What divides the right and left atria?
Septum primum and septum secundum.
How is blood shunted from the right atrium to the left atrium in an embryo?
Through the foramen ovale (of the septum secundum) and ostium secundum (of the septum primum).
What are the 3 possible causes of an atrial septal defect?
1. Ostium secundum overlaps foramen ovale.
2. Absence of septum secundum.
3. Neither septum secundum nor septum primum develop.
What structure grows to close the opening/canal between the atrial chamber and ventricular chamber into two smaller opening?
1. Superior endocardial cushion.
2. Inferior endocardial cushion.
What genetic abnormality is commonly associated with endocardial cushion defects?
Outline the pathway by which the heart tube forms the atria of the four-chambered heart.
1. Tube grows, elongates and folds into an S-shape.
2. Atrial chamber lays posteriorly in S, and ventricular chambers lays anteriorly in S.
3. Atrial chambers grows and incorporates into superior vena cava and pulmonary veins.
4. Septum primum forms from the middle top dividing the atrias, down to the endocardial cushion that sits in the middle of the heart, but not touching the cushion, leaving a hole called ostium primum.
5. Cell death in septum primum forms a hole called ostium secundum in the superior part of the septum priumum. This forms as the septum primum finally reaches the endocardial cushion.
6. Septum secundum forms incompletely right next to septum primum (leaving a hole called foramen ovale in the inferior part of the septum secundum).
Outline the pathway in which the ventricles and their outflow tracts are separated.
1. Ventricular chamber lays anteriorly in the S-shaped heart tube. This leads to muscular ventricular septum to form, dividing the ventricles.
2. Truncoconical swellings (ridges) of the truncus arteriosus meet, fuse and zip (both superiorly and inferiorly) in a 180 degree turn to form the spiral spetum (AKA aorticopulmonary septum).
3. Inferior portion of spiral septum meets with muscular ventricular septum to divide the ventricles and form the aorta and pulmonary arteries.
Name 6 different truncoconical (spiral) septum defects.
2. Ventricular septal defect (VSD).
3. Tetralogy of Fallot.
4. Persistent truncus arteriosus.
5. Transposition of the great vessels (RV to aorta, LV to PA(pulmonary artery))-Because the 180 degree spin did not take place.
Describe how the ventricles are remodeled in order to form the atrioventricular valves.
1. Myocardium erodes, leading to enlarged ventricles, which makes residual mesodermal tissue becomes fibrous and forms chordae tendinease.
2. Formation of papillary muscles and AV valves.
What does the truncus arteriosus become?
Gives rise to the great vessels: the proximal aorta and the proximal pulmonary trunck.
What does the bulbus cordis become?
The outflow track of both the right and left ventricles, the smooth parts of the ventricles.
What does the primitive ventricle become?
It becomes the trabeculated parts of the ventricles, the muscular parts.
What does the primitive atrium gives rise to?
Gives rise to the trabeculated part of both the atrias.
What does the sinus venosus turn to?
The left horn of the sinus venosus gives rise to coronary sinuses.
The right horn of the sinus venosus gives rise to smooth part of the right atrium.
What does the 1st aortic arch become?
Part of the maxillary artery.
What does the 2nd aortic arch become?
1. Stapedial artery
2. Hyoid artery
What does the 3rd aortic arch become?
It becomes two things:
1. Common carotid.
2. Proximal part of internal carotid.
What does the 4th aortic arch become?
The left part: Arch of adult aorta.
The right part: Proximal part of right subclavian artery.
What does the 5th aortic arch become?
What does the 6th aortic arch become?
It becomes two things:
1. Proximal part of pulmonary arteries.
2. Ductus arteriosus.
Which blood vessels carries oxygenated blood from the placenta to the fetus?
The umbilical vein. Veins carry blood back to the heart, notwithstanding the amount of oxygen.
What do we give to keep the PDA open?
What do we give to close a PDA?
NSAID like endomethacin.
Where embryological structure gives rise to the superior vena cava?
The right common cardinal vein and the right anterior cardinal vein.
What structure divides the truncus arteriosus into the aortic and pulmonary trunks? What is the cellular origin of this structure?
Aorticopulmonary septum. It is derived from the neural crest derivatives.
Which fetal vessel has the highest oxygenation?
Umbilical cord > Ductus venosus > Inferior vena cava > Right atrium.
What causes the ductus arteriosus to close?
Breathing. It increases oxygenated blood in aorta which leads to lower levels of prostaglandins, stopping the source that dialates the blood vessels.