Question

How would you compare the structures and functions of arteries, capillaries, and veins?

Answer 1

Artery takes blood away from heart to supply different organs while vein drains blood from different organs/brings blood towards the heart.
Both artery and vein are lined by three concentric tissue layers.

Explanation:

The tissue layers lining artery/vein are tunica externa, tunica media, and tunica interna.

1. Heart pumps blood in the arteries under high pressure.
2. Thus arterial walls are thick and tunica media is elastic.
3. Blood flows through arterial branches to reach various organs of the body.
4. Finest branches are called arterioles which divide in tissue capillaries inside an organ.
5. Arteries generally carry oxygenated blood, except pulmonary artery.

Capillaries are lined by only tunica interna, which is made of porous endothelium. The pores in the capillary endothelium (=simple squamous epithelium) allow amoeboid white blood cells (shown in black in the diagram) to travel into tissue space by a process called diapedesis where the WBCs help in removing invading pathogens and tissue debris.

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1. Heart receives blood drained by veins.
2. Large veins are formed by joining of tributeries draining from different organs.
3. Blood flows very slowly through veins: hence the lumen is wider. Wall of vein is thinner
4. To prevent back flow, the veins are equipped with internal valves.
5. Finest tributeries are called venules which arise from capillary beds.
6. Veins generally carry deoxygenated blood, except pulmonary vein.

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