Difference of Arteries and Veins and structure of human Heart (SA and AV node, definition semilunar valve) and more
Difference right side of the heart and left side of the heart
The left ventricle of the heart has in comparison to the right ventricle of the heart thicker walls. The underlying reason is that the left ventricle has to push the blood through the aorta and through the whole body to all the tissues and organs in order to supply them with oxygenated blood. That is why the left ventricle has more muscular walls. The right ventricle only has to push the blood to the lungs. Therefore, the right ventricle is less muscular as the way from the right ventricle to the lungs is quite short (in comparison with the way of the left ventricle).
Function and Importance of Semilunar Valve
Another extremely important feature of the left side of the heart is that is has semilunar valves, which open respectively close the way to the aorta. The mechanism is quite special as the valves will only open if the pressure inside the left ventricle is greater than the pressure of the aorta. So, the mechanism takes place automatically.
Function of SA (sinoatrial) node and AV (atrioventricular) node
Moreover, the right side of the heart has so-called SA (sinoatrial) and AV (atrioventricular) nodes. These nodes are another special feature, as the SA node conveys a stimulus through the atria and ventricles. It opens up the tricuspid and bicuspid valves and activates the AV node simultaneously, which will send off another impulse, which urges the left and right ventricle to contract.
Difference of arteries and veins
An artery always draws oxygenated blood from the heart to the organs and tissues. There are elastic and muscular arteries. Elastic arteries are always found right after the heart, because the heart has to push the blood with a great force with every heartbeat and this demands the arteries to be elastic (e.g. aorta). Otherwise, they would break.
A vein always draws deoxygenated blood from the organs or tissues (capillaries) to the heart (right atrium). An exception is the hepatic portal vein, which starts in the stomach and goes to the liver, where it will pass a capillary bed to oxygenize the blood. They also have a special pressure mechanism in order to be able to carry the blood to the heart. The pressure decreases to a minimum after passing the capillaries.