Name the 2 different types of valve in the heart

WHICH VENTRICLE IS THICKER ?

What are the 2 main arteries ?

WHAT ARE THE 2 MAIN VEINS?

WHAT CREATES THE 'LUB' SOUND IN A HEART BEAT?

WHAT DOES THE SINO-ATRIAL NODE DO?

why does the electrical impulse in the heart not go straight down from the top of the heart to the bottom?