Question

How do veins and arteries differ in structure?

Answer 1

Hint: The blood is carried to and from the heart with the help of a complex network of blood vessels, comprising arteries, veins, and capillaries. Arteries take the blood away from the heart to the body and lungs, while the veins carry the blood to the heart from the body and lungs. Capillaries connect arteries with the veins.

Complete answer:
Arteries are the blood vessels that carry blood away from the heart. Mostly, arteries carry the oxygenated blood (except pulmonary and the umbilical arteries). The major artery is the aorta which further branches into smaller arteries and carries blood from the heart to different parts of the body. The arteries carry oxygen and other nutrients to all the cells and remove carbon dioxide and waste products from them.
Arteries have three major layers. The outermost layer of the artery is called the tunica externa which is composed of collagen fibers and elastic tissue. Inside the tunica externa, tunica media is present which is a smooth layer of muscle cells, collagen fibers, and elastic tissue. The innermost layer, the tunica intima is in direct contact with the flowing blood. The elasticity of the blood vessels allows them to bend and fit at all places in the body. The inner cavity in which the blood flows is known as the lumen.
Veins are translucent but appear blue as only low-frequency light is absorbed that permits high-energy blue wavelengths to penetrate. They carry deoxygenated blood from the tissues to the heart and oxygenated blood from the lungs to the heart. The veins also have three layers (just like the arteries), but veins are less muscular (less strong) than arteries. They are even more closer to the skin as compared to the arteries. Unlike arteries, veins have valves that prevent the backflow of the blood because veins have to work against gravity so that blood can flow back to the heart. Usually, one-way valves are present in the veins.

Note: The arteries diverge into small vessels known as arterioles so that they can reach deeply into the muscles and other organs of the body. Arteries are made up of three different layers namely, tunica externa, tunica media and tunica intima.