Respuesta :

Due to a valve known as the septum primum, blood cannot return from the left atrium to the right.

Describe septum primum.

A thin, crescent-shaped membrane called the septum primum descends from the primitive atrium's roof in the direction of the growing endocardial cushions. The single basic atrium is divided into left and right parts by it.

What is the origin of septum primum?

The septum primum first forms as a muscular ridge that expands in the direction of the endocardial cushion tissue of the growing AV valves.

  • The original opening between the AV valves and the septum primum, known as the ostium primum, is finally sealed when it fuses with the cushion.

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