Final answer:
The part of the heart that cannot reach the brain is the pulmonary valve.
Step-by-step explanation:
The pulmonary valve is one of four valves that control blood flow in the heart. It's between the lower right heart chamber (right ventricle) and the artery that delivers blood to the lungs (pulmonary artery).
It cannot reach the brain and if the pulmonary valve cannot open, blood would not be able to reach the lungs. This would impede the circulation of blood beyond the heart, preventing it from reaching the rest of the body.
The pulmonary valve has three cusps: the anterior cusp (AC), the left cusp (LC), and the right cusp (RC). The tricuspid valve has three leaflets named the anterior (A), septal (S), and posterior (P). The pulmonary valve separates the right ventricular outflow tract of the right ventricle from the pulmonary trunk.