Formation of the Cardiac Septa

Question 1

The bulbus cordis will become the ______, the remaining 1/3 will form the ________. This area is now called the ___________ .

Answer 1

Primitive RV
Outflow portions of both the RV/LV
Conus cordis

Question 2

What does the truncus arteriosus give rise to?

Answer 2

The AO and PA trunks

Question 3

At this stage of development, the heart completely occupies the _________ , with the _______ and the ________ connected by the __________.

Answer 3

Pericardial cavity, with the Primitive LV on the left and the Bulbus cordis on the right connected by the Primary interventricular foramen.

Question 4

What occurs to the truncoconal section due to the rapid growth of the primitive atria?

Answer 4

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.

Question 5

How many days does it take for all of the septa to form?

Answer 5

10 days

Question 6

What structures are created as a result of the formation of the 7 cardiac septa?

Answer 6

4 chambers, 4 valves, a PA and AO

Question 7

What 3 structures are formed passively via the formation of cardiac septa?

Answer 7

The septum secundum of the atria, the muscular portion of the IVS, and the Aorticopulmonary area (RVOT,LVOT)

Question 8

What 3 structures are formed actively via the formation of cardiac septa?

Answer 8

The AV canal, the conus septum, and the truncus septum.

Question 9

What structure is formed first passively, then actively via formation of cardiac septa?

Answer 9

The atrial septum primum. This is the 7th septum.

Question 10

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 ___________.

Answer 10

Heart tube
Trabeculation
Interventricular foramen

Question 11

How are the borders of the interventricular foramen formed?

Answer 11

By the developing Interventricular Septum inferiorly and anteriorly, and by the bulboventricular flange superiorly and posteriorly.

Question 12

How are the ventricles enlarged?

Answer 12

By a process of centrifugal growth of the myocardium and the process of diverticulation and the increase of trabeculation internally.

Question 13

What happens to the trabeculation?

Answer 13

Some trabeculation will disappear. It’s reabsorbed. The remaining will later become papillary muscles, moderator band, and septal band.

Question 14

How is the muscular IVS formed?

Answer 14

It is formed by the medial walls of the growing ventricles, as they appose (face each other) and fuse, and become trabeculated.

Question 15

What does the trabeculation form in the RV?

Answer 15

The septal band, the moderator band, and the anterior papillary muscle.

Question 16

What does the trabeculation form in the LV?

Answer 16

The anterolateral and posteromedial papillary muscles.

Question 17

What purpose does the AV canal serve?

Answer 17

It is a communication between the atria and ventricles.

Question 18

What is the AV canal going to do?

Answer 18

It is going to divide into a right and left AV orifice.

Question 19

How does the AV canal divide into a right and left orifice?

Answer 19

It divides due to the opposing masses of mesenchymal tissue called endocardial cushions. These are the superior, inferior, lateral and medial cushions.

Question 20

In order for the AV canal to divide, what must the AV canal and truncoconal area do first?

Answer 20

They must realign themselves and shift medially.

Question 21

As the chambers dilate, what does the bulboventricular flange do?

Answer 21

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.

Question 22

What causes the AV canal to widen to the right and to the left?

Answer 22

This is a result of the endocardial cushions growing and extending into the lumen of the AV canal and approaching each other.

Question 23

The right and left endocardial cushions develop _____. The major cushions fuse, and ____________.

Answer 23

Prominences. The division of the AV canal is complete with both R/L atrioventricular orifice.

Question 24

When the cushions fuse to form the primitive RVIF/LVIF areas, what do the endocardial cushions then do?

Answer 24

They bend and form an arc with the concave side towards the LV and the convex side towards the atria.

Question 25

When the formation of the IAS is complete, what does the septum primum do?

Answer 25

The septum primum meets the convex side of the endocardial cushions and fuses.

Question 26

What does the portion to the left of the septum primum form?

Answer 26

The anterior Mitral valve leaflet.

Question 27

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 _______________.

Answer 27

Truncus swellings

Question 28

One swelling is located on the ___________ of the truncus, and the other is located on the _________ .

Answer 28

Dextrosuperior wall | Sinistroinferior wall

Question 29

The truncus swelling located on the dextrosuperior wall grows __________________ .

Answer 29

Distally and to the left

Question 30

The truncus swelling located on the sinistroinferior wall grows _________________ .

Answer 30

Distally and to the right

Question 31

As the truncus swellings of the dextrosuperior wall and of the sinistroinferior wall grow, they cause _________ .

Answer 31

Spiral septation of the truncus arteriosus.

Question 32

The formation of the truncus septum divides the truncus arteriosus into an _______ and ______ _____.

Answer 32

An aortic and pulmonary channel.

Question 33

During the septation of the _______, there are _______ in the conus cordis.

Answer 33

Truncus arteriosus | Conal swellings

Question 34

After the completion of the truncus arteriosus, the conal swellings start to _______________________ .

Answer 34

Grow toward each other and in a distal direction towards the truncal septum.

Question 35

There are 2 conal swellings. The __________ and the ____________.

Answer 35

* The dextrodorsal swelling which is continuous with the dextrosuperior truncus swelling. * The sinistroventral swelling which is continuous with the sinistroinferior truncal swelling.

Question 36

What do the swellings of the truncus arteriosus and the conus cordus form?

Answer 36

They form the spiral septation which seperates them into 2 great vessels. And they form the outflow tracks. RVOT and LVOT.

Question 37

What completes the partition of the truncus arteriosus?

Answer 37

The conal septum

Question 38

The growth of the RV causes ___________ of the AV canal so that the ___ ____ stops at the ________ .

Answer 38

A shift to the right. Dextrodorsal swelling. Superior border of the right AV orifice.

Question 39

Completion of the conus septum divides the conus into _________ .

Answer 39

An anterolateral portion and a posteromedial portion.

Question 40

What structures now form the RV?

Answer 40

The primitive RV and the anterolateral portion of the conus cordis.

Question 41

What has become continuous with and now helps to form the LV?

Answer 41

The posteromedial portion of the conus cordis and the fused AV endocardial cushions.

Question 42

With the completion of the _______ _______ , the originally large inter ventricular communication becomes smaller.

Answer 42

Conus Septum

Question 43

Final closure of the secondary inter ventricular foramen is accomplished by tissue derived mainly from the _______ _______ _______ .

Answer 43

inferior endocardial cushion