Progressive Care Nursing Certification (PCCN) Practice Exam

Which layer of the arterial vessel wall regulates the diameter of the artery?

1. Media

2. Intima

3. Externa

4. Adventitia

The correct answer is: Media

The correct answer, the media, is the layer of the arterial vessel wall primarily responsible for regulating the diameter of the artery. This layer consists of smooth muscle cells and elastic fibers, allowing it to contract and relax. When the smooth muscle in the media contracts, the artery narrows (vasoconstriction), and when it relaxes, the artery widens (vasodilation). This regulation is crucial for controlling blood pressure and adjusting blood flow to various tissues in response to the body's needs. The intima, which is the innermost layer of the blood vessel wall, serves primarily as a barrier between the blood and the vessel wall, contributing to vascular health and function but not directly involved in diameter regulation. The externa (also called the adventitia) is the outermost layer, providing structural support but also does not play a direct role in regulating the arterial diameter as it mainly contains connective tissue.