$A$ vein differs from an artery in having

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 does not have a muscular wall?

In a closed circulatory system, there is the presence of ........., but the absence of ..........

Arteries are best defined as the vessels which

Which blood capillaries are observed to study the circulatory system in a rat?