Development of interatrial septum and interventricular septum

By name you can understand what I am going to explain about; it's the septum between two atria and ventricles, the interatrial and interventricular septum, respectively. The topic is very simple, but I want you all to be more alert here, because it's a little bit tricky.

Let's start from above;

Development of Interatrial septum

In developing hearts, we all know that above will be the atrium and below will be the ventricle, and between the atrium and ventricle, there will be an endocardial cushion (ECC). This ECC is derived from splanchnopleuric LPM.In this particular topic, I will be discussing the formation of the interarterial septum. Let's dissect only the Atrium part and zoom it and try to understand the development.

In the diagram, we can see the right atrium and left atrium. ECC is also present on the bottom. Now with the development of heart septum forms, from the above, but it doesn't fully merge with the ECC, there is a formation of foramen before merging to the ECC, called foramen primum, and the formed septum is called septum primum.

 

Now hear me carefully; it's the trickiest part. So with time this septum primum gradually meets with ECC, but simultaneously, at the same time, there is a formation of another foramen in the middle, and that foramen will be the foramen secondum.

Most of us have a doubt on this matter, that both the foramen primum and foramen secondum are present on the same septum primum, but not at the same time.

Now, what's going to happen is that adjacent to this septum, there is a formation of another septum, which is going to descend down from above, but it is not going to meet with ECC, and again there will be a formation of an opening called the foramen ovale. Now what do we call the new septum? It's called Septum secondum. So, the foramen ovale is present on the septum secondum.

You can see in the diagram, it's the condition of the fetus before the birth. Blood will flow from the right atrium to the left atrium through the foramen ovale.

After birth, this foramen will be closed, and in place of this foramen there will be a depression called the fossa ovalis, and the margin of this fossa is called the limbus ovalis. It's interesting; now imagine here how the wall of the fossa and margin should have formed.

The floor of the fossa is formed by the septum primum, and the margin is by the septum secondum. So with the development of the baby, these septa will merge and form one interatrial septum.

Development of Interventricular Septum

This topic is not as complex as the previous one, but it's important. The interventricular septum has three parts:

1. Muscular part
2. Membranous part
3. Bulbar part

Only this here is to remember is from where these parts are derived.

First of all, the cardiac muscle present in the wall of the ventricle gives rise to an invagination, which forms the muscular part. A small part also arises from the ECC, which forms the membranous part.

For the Bulbar part, we have the remember, Spiral Septum, or Aorticopulmonary Septum, because this part is nothing but an extension of the Spiral Septum. Thus, forms by the neural crest cell.

This bulbar septum and spiral septum are jointly called the cono-truncal septum.

Now, with this we have completed our interventricular septum.

 

 

This is a brief blog about the development of septum between atria and ventricles. Hope you like it.

Thank you.