Which is the main structural feature that distinguishes elastic arteries from muscular arteries? Answer:
A – E A. Muscular arteries have vasa vasorum, elastic arteries do not
B. Muscular arteries do not have any elastic fibres, whereas elastic arteries are rich in elastic fibres
C. Muscular arteries have muscular cells throughout their wall, whereas elastic arteries do not have any
D. Elastic arteries have a significantly higher quantity of elastic fibres in the tunica media than muscular arteries
E. Muscular arteries have muscular cells only in the media, whereas elastic arteries do not have any
The correct answer and explanation is:
The correct answer is: D. Elastic arteries have a significantly higher quantity of elastic fibres in the tunica media than muscular arteries.
Explanation:
Arteries are classified based on their size and composition into elastic arteries and muscular arteries, and the key difference between them lies in the structure of their tunica media, the middle layer of the arterial wall.
Elastic arteries (e.g., the aorta and its major branches) are large vessels that must withstand and smooth out the high pressure generated by the heart’s contractions. To do this, their tunica media contains a high concentration of elastic fibres arranged in sheets or lamellae. These elastic fibres allow the artery to stretch during systole (heart contraction) and recoil during diastole (heart relaxation), which helps maintain continuous blood flow and dampens the pressure fluctuations. This elastic recoil function is vital in buffering the pulsatile output of the heart.
In contrast, muscular arteries (medium-sized arteries that distribute blood to organs and tissues) have a tunica media dominated by smooth muscle cells rather than elastic fibres. This muscle-rich layer allows these arteries to regulate their diameter actively through vasoconstriction and vasodilation, controlling blood flow and pressure downstream. While muscular arteries do contain some elastic fibres, they have significantly fewer than elastic arteries.
The other options are incorrect or misleading:
- A. Both muscular and elastic arteries can have vasa vasorum, small blood vessels that nourish the outer layers, especially in larger arteries.
- B. Muscular arteries do have elastic fibres, just fewer than elastic arteries.
- C. Elastic arteries do have smooth muscle cells in their tunica media, intermixed with elastic fibres.
- E. Elastic arteries do contain smooth muscle cells in the media; muscular arteries don’t lack them.
Thus, the defining feature is the quantity and prominence of elastic fibres in the tunica media—a hallmark of elastic arteries that distinguishes them from muscular arteries.