Embryology Flashcards
(35 cards)
Where is the cardiogenic area found prefolding?
It is found in front of the buccophalangeal membrane.
Describe what cephalocaudal folding does for the heart’s location.
This brings the heart down so that it is in the correct position, below the foregut
What happens to the cardiogenic area during lateral folding?
In lateral folding, the two cardiogenic areas are brought together and there is formation of the heart tube.
At what stage in development is there circulation in the embryo?
By the 4th week.
What are the regions of the primitive heart tube?
Aortic roots, truncus cordis, bulbous arteriosus, ventricle, atrium, sinus venosum.
What is the significance of the primative heart tube being tethered both cranially and caudally?
This means that as the tub groups is much remain with the same amount of space. This is what causes looping.
In what direction does the caudal portion move during looping?
It moves dorsally, cranially and to the left.
After looping, where are inflow and outflow in relation to each other?
They are both cranial. The inflow is Infront of the outflow.
What can be said about the vessels around the transverse pericardial sinus?
All the vessels in front flow in, and all the vessels behind flow out.
In the sinus venosum, in which direction does the venous return shift and what does this lead to?
Venous return shifts to the right. The left sinus recedes, becoming the coronary sinus and the right is engulfed by the right atria - enlarging it.
What structures from the primative heart tube go on to be part of the right atria?
Majority of the primative atrium and also the engulfed part of the sinus venosum - recieves drainage of blood from the body.
How does the left atria develop?
The left atria contains a small portion of primitive atrium. It sprouts a pulmonary vein and as it absorbs the proximal part of this, this leads to the pulmonary trunk and there being 4 holes into the atrium for blood to drain from the lungs
What can be said about the tissue absorbed from the pulmonary veins into the left atria?
It is smooth.
When does the oblique sinus form?
Is forms as the left atria enlarges and engulfs the pulmonary veins.
What organs must be bypassed in the fetal circulation?
The lungs - as they are not sufficiently developed.
The liver - this would use up all the nutrients in the blood.
In the fetus, where does oxygenated blood get delivered into in the heart?
The right atrium. It bypasses the right ventricle and lungs by moving into the left atrium.
What is the ductus arteriosus?
This is a vessel which joins the aorta and pulmonary trunk. In adults a ligamentous reminant may be seen of this.
What are they aortic arches in a fetus?
This is the initial, symmetrical, bilateral arrangements of 6 arches. Some regress and some go on to become important structures.
From which aortic arch is the arch of aorta derived from?
4th (left side) the right side of this forms the right subclavian artery.
Why is the 6th aortic arch also named the pulmonary arch?
The right side forms the right pulmonary artery and the left side forms the left pulmonary artery and the ductus arteriosus.
Describe the influence of the developing heart on the recurrent laryngeal nerves.
As the heart develops, it descends caudally. These nerves are hooked around the 6th aortic arch and so the right becomes hooked around the right subclavian artery and the left around the ductus arteriosus.
What is the name of the process which results in production of the 4 heart chambers?
Septation.
What happens at the beginning of septation?
Endocardial cushions push out into the middle of the heart, dividing it into left and right channels.
What is the septum primum?
This is the beginning of atrial septation and grows down onto the endocardial cushions. As it grows down the ostium primum is present but then before this closes the ostium secundum appears in the septum primum.
