interatrial Septum development

Development of interatrial septum

Leads to the division of common atrial chamber into right and left atrium

1. Spetum primum - Grows down from the roof of the primitive atrium toward the atrioventricular cushions

2. Foramen primum - Space between the free edge of the septum primum and AV cushions

3. With the growth of septum primum, this foramen becomes small and eventually gets closed

4. Septum secondum - With the closure of foramen primum, Septum primum near the roof of the atrium opens up a second foramen, the foramen secundum.

5. Septum secundum - Rigid septum on the right side of the septum primum from the roof of the atrium toward the AV cushions

6. Foramen ovale - Oval opening at the lower edge of septum secundum

7. Foramen ovale → Fossa ovalis

Immediately after birth, functional closure of the foramen ovale occurs because of pressure differences between the two atria:

a) Pressure drops in the right atrium because of decreased flow from the placenta

b) Pressure increases in the left atrium due to increased pulmonary venous return

Development of interventricular septum

It divides the common ventricular chamber into right and left ventricles.

The interventricular septum has two parts:

1. Muscular part
- Appears as a muscular ridge corresponding to the interventricular sulcus.
- It has two limbs and a free margin.
- Posterior limb advances towards the posterior endocardial cushion.
- Anterior limb approaches bulbs cordis.
- Free margin of the septum guards the interventricular foramen.

2. Membranous part
- This part of the interventricular septum has multiple origins.
a) Posterior endocardial cushion
b) Right bulbar ridge
c) Left bulbar ridge

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