American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

What structure in arterial walls helps to withstand increased blood pressure?

1. Nerves

2. Muscles

3. Endothelial cells

4. Connective tissues

The correct answer is: Muscles

The structure in arterial walls that helps to withstand increased blood pressure primarily consists of muscles, specifically smooth muscle cells found in the middle layer of the arterial wall, known as the tunica media. This layer is crucial because it is responsible for the elasticity and contractility of the artery. When blood pressure rises, these smooth muscles can contract to help regulate the diameter of the artery, which in turn helps to manage blood flow and pressure. In addition to the muscle layer, connective tissues also play an important role by providing structural support and elasticity, allowing the arteries to stretch and recoil as blood is pumped through them. However, it is the muscular layer that is primarily responsible for actively responding to changes in blood pressure through contraction and relaxation. The endothelial cells lining the arterial walls facilitate smooth blood flow and act as a barrier to control the passage of substances; however, they do not have a direct role in mechanical resistance to blood pressure. Nerves contribute to the regulation and coordination of vascular responses, but they do not structurally resist pressure. Thus, while all these components are vital for arterial function, the smooth muscles are key to coping with increased blood pressure.