Varicose Veins – 40 Informal Points Introduction

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  1. Use the Internet to research the structure of arteries and veins as well as the science behind varicose vein formation. Pay attention to the structural differences between the vessels and think about the force of blood flow in each type. As you complete your research answer the questions in numbers 3 – 7.

  2. How do arteries and veins differ in structure?

Blood Vessel Types



  • Carries oxygenated blood AWAY from the heart

    • Exception: Blood flowing through the pulmonary artery is deoxygenated.

  • Thick, elastic muscle layer that can handle high pressure as blood pulses through it

  • Red vessels

  • Aorta  Artery  Arteriole  Capillary

  • Carries deoxygenated blood TO the heart

    • Exception: Blood flowing through the pulmonary vein is oxygenated.

  • Thin, elastic muscle layer

  • Blue vessels (although the blood is NOT blue)

  • Vein  Venule  Capillary

  1. What are varicose veins?

Arteries carry blood from your heart to the rest of your tissues. Veins return blood from the rest of your body to your heart, so the blood can be recirculated. To return blood to your heart, the veins in your legs must work against gravity.

Muscle contractions in your lower legs act as pumps, and elastic vein walls help blood return to your heart. Tiny valves in your veins open as blood flows toward your heart then close to stop blood from flowing backward.

  1. How do varicose veins form?

Veins have valves that act as one-way flaps to prevent blood from flowing backwards as it moves up your legs. If the valves become weak, blood can leak back into the veins and collect there. (This problem is called venous insufficiency.) When backed-up blood makes the veins bigger, they can become varicose.

  1. Why is it that people develop varicose veins, but not varicose arteries?

Varicose arteries do not exist because not only are they located much deeper in the skin than veins, but they are also equipped to handle blood with a higher pressure due to their thick elastic muscular walls. Also, arteries are not working against gravity as much; most arteries are taking blood downward from the heart and work with gravity, not against it like most veins.

  1. How is blood helped in its return back to the heart? You must mention the role of at least two other body systems.

Both the superior and inferior vena cava allow blood to be taken back into the heart. Veins do not have thick muscular walls with which to send the blood though, so they must rely on other muscles throughout the body to help them get the blood back to where it needs to be. The skeletal system helps them push the blood back to the heart.

Conclusion Questions

  1. What do you notice about the width of an artery wall versus the width of a vein wall? Why does this make sense given the function of the vessels?

Arteries have much thicker muscular walls than veins. This makes sense since arteries are transporting high pressure blood throughout body; the pressure in veins is much lower.

  1. Capillaries function in gas exchange. Describe at least two ways capillary structure is related to this function.

Capillaries have membranes that are one cell thick making the gas exchange of O2 and CO2 quick and efficient. They are also small and numerous to reach all parts of the body effectively.

  1. How do capillaries interact with the respiratory system? Make sure to mention specific structures of the respiratory system.

Description of how circulatory System and Respiratory System work together

  • Gas exchange (O2 <--> CO2) occurs through the cell membranes of capillaries (smallest cell in the circulatory system) and alveoli (smallest cell in the respiratory system.)

    • Alveoli are the tiny “grape-like” cell structures in the lungs that expand when inhaling and contract when exhaling during breathing.

  • The cell membranes of capillaries and alveoli touch.

  • When deoxygenated, blood carrying CO2 enters the capillaries in the lungs, the CO2 diffuses across the capillary membrane and the alveoli membrane to leave the circulatory system and enter the respiratory system to be exhaled out of the body.

  • When a person inhales they bring O2 into their alveoli, which diffuses across the alveoli membrane and the capillary membrane to enter the blood stream. The blood is then sent to the heart to be pumped out to the body.

  1. Which artery do you think is made of thicker muscle, the aorta or the pulmonary artery? Why? Refer back to your heart box to visualize the path of these vessels.

Aorta because it must hold and send blood long distances throughout the entire body whereas the pulmonary artery only has to send blood a short distance to the lungs.

  1. Explain why a person who spends most of the day on his/her feet is more likely to develop varicose veins.

A person that spends most of the day on his/her feet is constantly subjecting their legs to gravity, which veins are fighting against to move blood back to the heart.
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