Arterial Wall Composition

Steps:

• Identify the layer X in the transverse section as part of the artery's tunica media or overall wall.
• Recall that arteries contain elastic fibres for stretch and recoil, collagen for strength, and smooth muscle for contraction.
• Match the tissues to standard histological features: elastic fibres in intima/media, collagen in all layers, smooth muscle in media.
• Confirm all three are essential for arterial function, ruling out incomplete lists.

Why D is correct:

• Arteries feature elastic fibres (for elasticity), collagen (for tensile strength), and smooth muscle (for vasoconstriction), as defined in vascular histology.

Why the others are wrong:

• A: Excludes elastic fibres, essential for arterial elasticity.
• B: Excludes collagen, needed for structural support.
• C: Excludes smooth muscle, required for blood pressure regulation.

Final answer: D