An aortic aneurysm is defined as what?

An aortic aneurysm is characterized by a weakness and subsequent dilation of the vessel wall, particularly the aorta, which is the largest artery in the body. This dilation occurs when the structural integrity of the vessel wall is compromised, most often due to factors such as hypertension, atherosclerosis, or genetic conditions that affect connective tissue. When the wall weakens, it can expand and form a bulge, leading to the risk of rupture if not monitored or treated appropriately. This dilation represents a significant clinical risk, as a ruptured aortic aneurysm can lead to life-threatening internal bleeding.

The other options do not accurately describe an aortic aneurysm. Thinning of the arterial wall can occur in some contexts, but it's the combined aspects of weakness and dilation that specifically define an aneurysm. Hardening of the blood vessels typically refers to atherosclerosis and does not capture the essence of an aneurysmal condition. Complete blockage of the artery describes a different pathology, such as an artery occlusion, which is distinct from an aneurysm's nature of dilation. Thus, the definition that encompasses the characteristics of an aortic aneurysm is indeed the weakness and subsequent dilation of the vessel wall.