Final answer:
The dilatation of a segment of a vessel wall caused by weakness of all three layers of the vessel wall is called aneurysm, making the statement true.
Step-by-step explanation:
The answer to the question is a. true. Dilatation of a segment of a vessel wall caused by a weakness of all three layers of the vessel wall is known as aneurysm. With an aneurysm, the weakened vessel wall bulges and can potentially rupture. This condition can occur in different types of blood vessels, such as arteries or veins. It's important to recognize that a healthy elastic artery, in contrast to a weakened one, is compliant and facilitates blood flow, rather than reducing it or being a resistance artery with a thin wall and irregular lumen. Increased blood viscosity does not increase blood flow; in fact, it may do the opposite. Tissue injury and inflammation can lead to reduced compliance of arteries and conditions such as atherosclerosis, which stiffens and scars artery walls, while plaque buildup can impair blood flow.
For example, an abdominal aortic aneurysm is an aneurysm that occurs in the aorta, the main blood vessel that supplies blood to the abdomen, pelvis, and legs. If left untreated, it can be life-threatening.