Tuesday, May 17, 2016

What are the differences between Arteries and Veins?

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What are the differences between Arteries and Veins?
Tuesday, May 17, 2016

What are the differences between Arteries and Veins?
Are there valves in arteries?

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Difference between Arteries and Veins
~ My Notes from Wikipedia
(My Notes from Wikipedia is exactly the same, except that it is presented in a way that my mind can easily absorb because it starts with things I find easy to understand first so that it's easier to add on the things that are more difficult later. This helps me to cover more before difficulty slows me down.)

Veins are blood vessels that carry blood toward the heart. In contrast to veins, arteries carry blood away from the heart. Veins are often closer to the skin. There are valves in most veins to prevent backflow.

Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart.

Veins are less muscular than arteries.
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From Wikipedia

Veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart.
Veins are less muscular than arteries and are often closer to the skin. There are valves in most veins to prevent backflow.
~ https://en.wikipedia.org/wiki/Vein
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https://www.quora.com/Why-dont-arteries-have-valves/answer/Roman-Saini

Roman Saini
Roman Saini, Dissected them during medicine days.
13.9k Views • Roman has 11 endorsements in Medicine and Healthcare.



Main function of valve is to prevent back flow of blood. This is because blood pressure in veins is very low (compared to arteries). 

There is no need of valves in the arteries because the blood pressure usually varies between 70-110 mm Hg. 

Imagine you have just opened a tap with full flow in a washroom and you applied your hand at the outflow. That is just 50-60 mm Hg (in normal circumstances). It's impossible for water to back flow when such a tremendous amount of pressure is applied from the origin. 

One of my friend nicked a patient's artery by mistake and blood literally sprayed 6-7 feet in the air. That's the kind of strong pressure I'm talking about. Anyway, if the valves (especially sapheno-femoral valve) in the lower limbs fail, back flow of blood is visible from the naked eye in the form of tortuousity. It is called varicose veins.




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https://www.quora.com/Why-dont-arteries-have-valves/answer/Mary-Snider-1

Mary Snider
Mary Snider, Philospher!
151 Views




Veins have valves to prevent blood from flowing backwards and pooling, whereas arteries pump blood at higher pressures, which naturally prevents backflow. 

Veins need valves to keep blood flowing in one direction because the flow is less constant; the flow in arteries is constant and requires artery walls to be more flexible and strong enough to accommodate the high pressures.

The valves in veins allow blood flow in one direction while blocking any counter-flow. These valves assist the body in sending blood in the correct direction; for example, blood flow must work against gravity to move blood from your legs back toward your heart. The valves ensure success, as they keep blood moving forward in the veins.

While these valves work quite efficiently when intact, they tend to break down during aging or when people are inactive for long periods of time. These breakdowns allow blood to pool where the valves are not working effectively. Such pooling leads to varicose veins.

Rather than requiring valves to regulate blood flow, arteries require flexible walls that can withstand great pressure to accommodate the flow. The constant motion of blood in arteries ensures that blood is always pushed forward; it does not flow backwards because of the blood behind it.

Instead, arteries must deal with increases in pressure when blood flow increases; as a result, arteries have walls that expand and contract in response to the pressure of the flowing blood.
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