Dr. Seiden - Embryology Flashcards
Order of the heart tube from caudal to cranial
Sinus venosus –> atrium –> ventricle –> bulbous cordis –> truncus arteriosus
How does the heat tube change?
1) The things that remain Arteries/veins will remain the same size. The things that turn into atria and ventricles will get larger.
2) We also see the heart tube begin to fold on itself.
What are two ways that we see enlargement in the right atrium?
1) first way is by layering cells on top of each other and then sculpting out, which will form the rough walled trabeculae carnae and pectinate muscle.
2) The analogy he gave was that you have a house and a backyard and your two neighbors have houses and backyards. You want a bigger backyard so you tear down the fence and take over their backyards. However, we used different color seeds so we can see whos yard was originally whose. We see the same thing here where we see the rough walled area called “sinus venosus” taking over the smoothed wall area, called “sinus vvenarum”, but we can still tell which one was which because one is smooth and one is rough. Sinus Venarum is where the veins came into the right atrium, so we see that all of the SVC, IVC, and coronary sinus will all enter smooth wall.
Sinus venosus
Sin venaram
Venosus - rough walled area
Venaram - smooth walled area that the SVC, IVC, and coronary sinus enter into
How do we develop smooth muscle in the left atrium?
As we know, the pulmonary veins carry oxygenated blood back to the left ventricle. These veins used to protrude much further out and have a left and right branch. Eventually they recede into the wall o the left atrium and become part of the wall.
What is the result of heart tube folding?
1) Originally we saw that the atrium was below the ventricle and only after the folding we see that the atrium is above the ventricle.
2) We also see that the veins began inferior caudal and the arteries began cranial. After folding, we see the Arteries are anterior and the veins are posterior.
Endocardial Cushions
Ingrowths from the wall in between atria and ventricle. They are derived from the neural crest. They will eventually grow towards and fuse to the septum primum.
Primum Type ASD
If septum primum and endocardial cushions don’t need and fuse there will be a persistent foramen primum.
- Child is acyonotic
- —- because you are moving oxygenated blood into unoxygenated side.
Secundum type ASD
To much apoptosis in septum primum that the septum secundum no longer covers septum primum and foramen ovale will never close.
- child will be acyonotic
- —- again, because the blood is moving from left->right
Tetralogy. Of Fallot
Cyanotic defect that is really one thing that causes four things. The cyanosis tends to occur later in life. The aorticoventricular septum is in the wrong spot. Because of this, we see 4 signs:
1) aortic overriding
2) pulmonic stenosis
3) right ventricular hypertrophy
4) ventricular septal defect
Persistent Truncus Arteriosus
The ventricular septum will just never form. Because of this you will have deoxygenated blood and oxygenated blood mixing together In one large vessel. They split up later on so there will be partially oxygenated blood in both vessels.
Transposition of the great arteries
Cyanotic defect where we see that the pulmonary trunk and aorta do not spiral like they are supposed to. As a result, if you think about it, if the aorta comes out of the right and stays right and the pulmonary trunk comes out of the left and stays left, then both will be involved in closed circuits where the dexogynated blood will be returned to the same place as will the oxygenated blood. We would expect them die right away. But they don’t. There must be some other defect that is responsible for keeping them alive. One thing that can be done is that you can create a bigger defect.
Three branches of aortic trunk
Brachiocephalic trunk
Common carotid
Left subclavian
Pathway of blood before birth
1) partially oxygenated blood travels from the umbilical arteries
2) The blood goes out to the placenta and picks up oxygen
3) The oxygenated blood leaves the placenta thru the umbilical vein
4) Oxygenated blood travels through the umbilical vein past the liver, heading towards the IVC
5) systemic venous return also heads towards the IVC via the ductus venosus
6) Flows mix in the IVC and the blood is partially oxygenated.
7) Coming into the SVC is venous return, which is fully deoxygenated
8) the portion that went into the IVC will go straight to the foramen ovale. It will go out of the left atrium to the left ventricle to the ascending aorta.
9) The portion that went into the SVC will enter the right atrium and go through the tricuspid valve into the right ventricle and outs of the pulmonic trunk. Most of this blood will enter aortic circulation via the ductus arteriosus.
In a fetus are ascending aorta and descending aorta the same with regards to what type of blood is in it?
No, ascending aorta will be more oxygenated.
