In the embryonic heart, the crista terminals separates what two structures?
Sinus venosus and embryonic atrium.
What structure is located in the crista terminalis?
How does fetal blood flow circulate?
Umbilical vein -> ductus venosus bypasses liver -> IVC/SVC -> foramen ovale and foramen secundum bypass right ventricle -> left atrium -> left ventricle -> aorta. Blood that does go through the right ventricle goes through the pulmonary artery and into the aorta, bypassing the lungs.
When do most congenital heart defects form?
Weeks 3-8. This is because the heart is forming at this period and often, mothers don't even know they're pregnant at this point.
What is the most common cause of congenital heart defects?
Trisomy 21. AV septal and valve defects.
What environmental factors can cause congenital heart defects?
Congenital rubella infection, gestational diabetes and teratogens.
What are the main categories of congenital heart defects?
Left to right shunt, right to left shunt and obstruction
blockage or absence of a normal opening
Instead of arching to the left the aorta is displaced to the right so that it appears to arise from both ventricles.
Why wouldn't a left to right ASD cause blue baby?
Because oxygenated blood is being shunted away and tissues continue to get oxygenated blood.
In an adult there is a hole in the atrial septum. What structure is absent?
Septum secundum. It is the second wall that divides the atria into two sides.
What abnormalities can cause formation of an atrial septal defect?
1) Excessive resorption of the septum primum 2) Large formation of oval foramen caused by a short septum primum 3)Septum secundum does not form 4) Common atrium
Why would someone really want their ASD corrected?
Blood clots are likely to form in the right atrium. Smaller blood clots are not as big of a problem in the lungs. If the clot can get into the left atrium, a smaller clot can easily cause a stroke.
Developmental defects in the endocardial cushions can result in what congenital heart defects?
ASD (foramen primum does not close), VSD (IV septum does not close) and AVSD (atrioventricular septum is open)
What portions of the AV valves would be absent in an AVSD?
The septal leaflet of the tricuspid and anterior leaflet of the mitral valve.
What is the most common congenital heart defect? What causes these?
VSD. 1) Deficient swelling from conotruncal septum 2) Failure of endocardial cushion fusion. 3) Insufficient development of muscular septum. This causes high pressure blood in the left to flow to the right.
How does the tetralogy of Fallot cause blue baby syndrome?
The defects ultimately result in a right to left shunt, putting deoxygenated blood into systemic circulation. 1) Pulmonary stenosis 2) Patent ductus arteriosus 3) Overriding aorta 4) interventricular septal defect 5) Enlarged right ventricle.
Where do the outflow tracts form from?
What can you give a premature baby to keep its ductus arteriosus open? When would you do this? What other structure would you hope is still there?
Prostaglandins. You would do this in the event of aortic coarctation, aortic valvular atresia, and transposition of the great vessels. You would hope the patent foramen ovale is still there so oxygenated blood can flow left to right, go out the pulmonary artery, through the ductus arteriosus, into the aorta and into the periphery.
How does a patent ductus arteriosus cause strain on the heart?
Higher pressure in the aorta pushes blood from the aorta into the pulmonary artery. This will increase pressure in the heart.
Why do babies fail to thrive when there is a persistent truncus arteriosus?
The truncus arteriosus normally separates into the aortic an pulmonary arteries down at the ventricular level by the conotruncal septum. Failure of this septum to form results in VSD and a single outflow tract with no specification of blood for the lungs or blood for the periphery.
What are the different types of truncus arteriosus are there?
Pulmonary arteries come off trunk close together, they come off independently or they come off the thoracic aorta.
How can malformations in the conotruncal septum (aorticopulmonary trunk) result in pulmonary stenosis? Aortic stenosis? Valve malformations?
Why would you try to maintain the ductus arteriosus and hope there was a patent foramen ovale in a baby with pulmonary valvular atresia?
So that blood from the vena cava can flow from right to left atria, into the left ventricle, out the aorta, through the patent ductus arteriosus and into the lungs to be oxygenated.
Which aortic arch disintegrates? What clinical symptoms may present when this arch does not disintegrate?
The right portion of the dorsal aorta (aortic arch 6). When this doesn't disintegrate a vascular ring forms around the trachea and the esophagus. The patient may experience dysphagia from squeezing of the esophagus by the vessels.
What type of aortic coarctation is most serious?
A post-ductal aortic coarctation. This happens past the ductus arteriosus and the baby must then develop a collateral circulation (via sublclavian and internal thoracic arties) because the ductus arteriosus can't help out at all.
Where does blood go without impedance in aortic coarctation?
When would a ligamentum arteriosum cause dysphagia in a patient?
When a right aortic arch forms and the ligamentum arteriosum forms a ring around the trachea and esophagus.
How does the body maintain blood supply when the 4th aortic arch is obliterated or interrupted?
The patent ducts arteriosus takes blood to the thoracic aorta and the right aorta persists in order to maintain blood flow to the extremities (although it will be decreased significantly)
How do you get blood flow to your right arm if the right 4th aortic arch was obliterated?
Usually the 4th aortic arch forms the right sublacian artery and the left aortic arch. If it doesn't form on the right then it will come from the 7th intersegmental artery from the dorsal aorta.