Formation of the Cardiac Septa Flashcards
The bulbus cordis will become the ______, the remaining 1/3 will form the ________. This area is now called the ___________ .
Primitive RV
Outflow portions of both the RV/LV
Conus cordis
What does the truncus arteriosus give rise to?
The AO and PA trunks
At this stage of development, the heart completely occupies the _________ , with the _______ and the ________ connected by the __________.
Pericardial cavity, with the Primitive LV on the left and the Bulbus cordis on the right connected by the Primary interventricular foramen.
What occurs to the truncoconal section due to the rapid growth of the primitive atria?
This causes the truncoconal section of the bulbus cordis to shift from a lateral to a more medial location.
- The truncus arteriosus sits in the depression between the right primitive atria and the left primitive atria.
- The conus cordis assumes an oblique position between the roof of the primitive LV and the anterolateral wall of the RA.
How many days does it take for all of the septa to form?
10 days
What structures are created as a result of the formation of the 7 cardiac septa?
4 chambers, 4 valves, a PA and AO
What 3 structures are formed passively via the formation of cardiac septa?
The septum secundum of the atria, the muscular portion of the IVS, and the Aorticopulmonary area (RVOT,LVOT)
What 3 structures are formed actively via the formation of cardiac septa?
The AV canal, the conus septum, and the truncus septum.
What structure is formed first passively, then actively via formation of cardiac septa?
The atrial septum primum. This is the 7th septum.
At this stage of development, the RV/LV are still just a widening of the ______ and _______ has just started.
The RV/LV are still connected by the ___________.
Heart tube
Trabeculation
Interventricular foramen
How are the borders of the interventricular foramen formed?
By the developing Interventricular Septum inferiorly and anteriorly, and by the bulboventricular flange superiorly and posteriorly.
How are the ventricles enlarged?
By a process of centrifugal growth of the myocardium and the process of diverticulation and the increase of trabeculation internally.
What happens to the trabeculation?
Some trabeculation will disappear. It’s reabsorbed. The remaining will later become papillary muscles, moderator band, and septal band.
How is the muscular IVS formed?
It is formed by the medial walls of the growing ventricles, as they appose (face each other) and fuse, and become trabeculated.
What does the trabeculation form in the RV?
The septal band, the moderator band, and the anterior papillary muscle.
What does the trabeculation form in the LV?
The anterolateral and posteromedial papillary muscles.
What purpose does the AV canal serve?
It is a communication between the atria and ventricles.
What is the AV canal going to do?
It is going to divide into a right and left AV orifice.
How does the AV canal divide into a right and left orifice?
It divides due to the opposing masses of mesenchymal tissue called endocardial cushions. These are the superior, inferior, lateral and medial cushions.
In order for the AV canal to divide, what must the AV canal and truncoconal area do first?
They must realign themselves and shift medially.
As the chambers dilate, what does the bulboventricular flange do?
The bulboventricular flange will need to recede as the IVS grows and shifts so that it is now aligned with the primitive LV and the conus cordis.
What causes the AV canal to widen to the right and to the left?
This is a result of the endocardial cushions growing and extending into the lumen of the AV canal and approaching each other.
The right and left endocardial cushions develop _____. The major cushions fuse, and ____________.
Prominences. The division of the AV canal is complete with both R/L atrioventricular orifice.
When the cushions fuse to form the primitive RVIF/LVIF areas, what do the endocardial cushions then do?
They bend and form an arc with the concave side towards the LV and the convex side towards the atria.
When the formation of the IAS is complete, what does the septum primum do?
The septum primum meets the convex side of the endocardial cushions and fuses.
What does the portion to the left of the septum primum form?
The anterior Mitral valve leaflet.
During the division of the AV canal in the truncoconal area of the bulbus cordis, 2 opposing areas of tissue appear in the mid truncus called _______________.
Truncus swellings
One swelling is located on the ___________ of the truncus, and the other is located on the _________ .
Dextrosuperior wall
Sinistroinferior wall
The truncus swelling located on the dextrosuperior wall grows __________________ .
Distally and to the left
The truncus swelling located on the sinistroinferior wall grows _________________ .
Distally and to the right
As the truncus swellings of the dextrosuperior wall and of the sinistroinferior wall grow, they cause _________ .
Spiral septation of the truncus arteriosus.
The formation of the truncus septum divides the truncus arteriosus into an _______ and ______ _____.
An aortic and pulmonary channel.
During the septation of the _______, there are _______ in the conus cordis.
Truncus arteriosus
Conal swellings
After the completion of the truncus arteriosus, the conal swellings start to _______________________ .
Grow toward each other and in a distal direction towards the truncal septum.
There are 2 conal swellings. The __________ and the ____________.
- The dextrodorsal swelling which is continuous with the dextrosuperior truncus swelling.
- The sinistroventral swelling which is continuous with the sinistroinferior truncal swelling.
What do the swellings of the truncus arteriosus and the conus cordus form?
They form the spiral septation which seperates them into 2 great vessels.
And they form the outflow tracks. RVOT and LVOT.
What completes the partition of the truncus arteriosus?
The conal septum
The growth of the RV causes ___________ of the AV canal so that the ___ ____ stops at the ________ .
A shift to the right. Dextrodorsal swelling. Superior border of the right AV orifice.
Completion of the conus septum divides the conus into _________ .
An anterolateral portion and a posteromedial portion.
What structures now form the RV?
The primitive RV and the anterolateral portion of the conus cordis.
What has become continuous with and now helps to form the LV?
The posteromedial portion of the conus cordis and the fused AV endocardial cushions.
With the completion of the _______ _______ , the originally large inter ventricular communication becomes smaller.
Conus Septum
Final closure of the secondary inter ventricular foramen is accomplished by tissue derived mainly from the _______ _______ _______ .
inferior endocardial cushion
