MICROANATOMY

Detailed explanation-1: -Compared to arteries, veins are thin-walled vessels with large and irregular lumens (see Figure 6). Figure 6. Many veins have valves to prevent back flow of blood, whereas venules do not. In terms of scale, the diameter of a venule is measured in micrometers compared to millimeters for veins.

Detailed explanation-2: -Arteries are more muscular and have smaller, rounder lumens (internal spaces) than veins. The artery lumen has a wavy endothelium, or inner lining, due to the configuration of elastic tissue beneath it.

Detailed explanation-3: -Capillaries are tiny, extremely thin-walled vessels that act as a bridge between arteries (which carry blood away from the heart) and veins (which carry blood back to the heart).

Detailed explanation-4: -The superior vena cava is the large vein that brings blood from the head and arms to the heart, and the inferior vena cava brings blood from the abdomen and legs into the heart.