What structure enters the upper part of the interventricular septum and divides into right and left bundle branches?

The structure that enters the upper part of the interventricular septum and divides into right and left bundle branches is the AV bundle, also known as the bundle of His. This specialized cardiac conducting tissue is crucial for the propagation of electrical signals from the atria to the ventricles.

When an electrical impulse originates from the sinoatrial (SA) node, it travels through the atria and reaches the atrioventricular (AV) node. From there, the impulse moves into the AV bundle, which extends into the interventricular septum. Once in this area, the AV bundle splits into the right and left bundle branches, facilitating coordinated contraction of both ventricles by allowing the impulse to reach them simultaneously. This is essential for maintaining an effective heartbeat and ensuring that blood is pumped efficiently from the heart.

Other options represent different components of the cardiac conduction system or structures unrelated to the division into bundle branches. The SA node is responsible for initiating the heartbeat, the atrioventricular node serves as a gatekeeper that regulates impulses between the atria and ventricles, and the pulmonary trunk is a vessel that carries blood from the right ventricle to the lungs. Each plays a unique role, but none is responsible for the division