Veins are described as which?

• A. High-pressure ducts
• B. Arterial-appearing tubes
• C. Not part of the venous system
• D. Dilated or collapsible

Answer: (D)

Veins are low-pressure, highly compliant vessels that readily distend and collapse. Their thin walls and limited smooth muscle allow them to dilate with increased venous filling or pooling and to collapse when external pressure is applied or when they’re empty. This makes them appear dilated when distended and easily compressible on ultrasound. In contrast, arteries are high-pressure, thick-walled, and not easily compressible, so describing veins as dilated or collapsible best reflects their physiological behavior. Veins are indeed a fundamental part of the venous system, not separate from it.