THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -Veins. A vein is a blood vessel that conducts blood toward the heart. Compared to arteries, veins are thin-walled vessels with large and irregular lumens (see Figure 18.2. 2).

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. Arteries and veins often travel in pairs using the same connective tissue pathways.

Detailed explanation-3: -Blood capillaries have a very thin lumen for the proper exchange of nutrients and gases. The lumen of the capillaries is very small because the blood flow here is too slow for the maximum exchange process. The capillaries also lack thick muscular walls.