Which of the layer of the artery contains smooth muscles?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Applied Anatomy

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Explanation

The tunica media is the middle layer of an artery's wall.
It is the thickest layer in arteries and is composed primarily of circularly arranged smooth muscle cells and elastic fibers.
The smooth muscle in the tunica media allows for vasoconstriction (narrowing) and vasodilation (widening) of the vessel.
This ability to change diameter is crucial for regulating blood flow and maintaining blood pressure throughout the body.

Option A: The tunica interna (or intima) is the innermost layer. It consists of a single layer of endothelial cells and provides a smooth surface for blood flow, but it does not contain a significant amount of smooth muscle.
Option C: Tunica alba is not a layer of a blood vessel. The term 'alba' means white, and it is used in other anatomical structures like the linea alba (in the abdomen) or tunica albuginea (covering the testes), which are fibrous connective tissues.
Option D: The tunica externa (or adventitia) is the outermost layer. It is composed mainly of connective tissue (collagen fibers) that protects and anchors the vessel. It does not contain the primary layer of smooth muscle responsible for regulating vessel diameter.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of Arterial Walls as background academic context rather than a clinical decision trigger.
Understanding the tunica media is vital for comprehending hypertension. Chronic high blood pressure can cause the smooth muscle in the tunica media to hypertrophy (thicken), leading to narrowed arteries and increased vascular resistance.
Many blood pressure medications, such as calcium channel blockers and other vasodilators, work by relaxing the smooth muscle cells in the tunica media, causing the arteries to widen and lowering blood pressure.
In atherosclerosis, plaque builds up in the tunica intima, but this can weaken the underlying tunica media, leading to complications like aneurysms (abnormal bulging of the artery wall).

How to Approach the Question

This is a factual recall question about anatomy.
First, identify the key components of the question: 'layer of the artery' and 'contains smooth muscles'.
Recall the three layers of a blood vessel wall: intima, media, and externa (or adventitia).
Associate the primary function with each layer. The intima is for smooth lining, the media is for contraction/dilation, and the externa is for support.
The function of contraction and dilation requires muscle. Therefore, the middle layer, the tunica media, must be the one containing smooth muscle.
Evaluate the options provided. 'Tunica media' directly corresponds to the middle layer. 'Tunica alba' is an unfamiliar term in this context and is likely a distractor.

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