Which vein carries oxygenated blood, unlike all other veins?

What are blood vessels composed of?

Assertion : When there is a fall in the blood pressure due to loss of blood volume,this is compensated by vasoconstriction of veins.
Reason : Veins hold the extra amount of blood which can be shifted to the arteries as required.

Which of the following is devoid of valves?

Which of the following does not have a muscular wall?

$A$ vein differs from an artery in having