ANATOMY

Detailed explanation-1: -The vena cava are the two largest veins that carry blood into the right upper chamber of the heart (the right atrium).

Detailed explanation-2: -Veins are generally larger in diameter, carry more blood volume and have thinner walls in proportion to their lumen. Arteries are smaller, have thicker walls in proportion to their lumen and carry blood under higher pressure than veins.

Detailed explanation-3: -The size of the veins closest to the heart is the largest among all the vessels.

Detailed explanation-4: -Arteries are the largest blood vessels with the thickest walls, and capillaries are the smallest.