Asked in Arteries
Why is the wall of the aorta thicker than the wall of the pulmonary trunk?
To put it simply:
The blood in the aorta has to go all around the body. Blood in the pulmonary trunk has to go all around the lungs. The body is, obviously, larger than the lungs. This means blood going around the body needs to be "pushed" more. This is because there is more resistance. For example, it's harder to push a car for 1 mile, then it is to push it 1 metre.
Because the blood has to be pushed more, the heart (left ventricle) pumps it out at a higher pressure. Similarly, because the blood going around the lungs doesn't need to go so far, the heart (right ventricle) pumps it out at a lower pressure.
Because the blood in the aorta is at higher pressure than the pulmonary trunk, it needs to have thicker walls. For example a fire hose is thicker than a garden hose because it needs to transport water at a higher pressure.
The aorta contains large amount of smooth muscle and elastic tissue to help it cope with the high blood pressure.