Difference between arteries and veins

[277190]

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What are the structural and functional differences between arteries and veins? Do veins have smooth muscle? If so, is it less than the smooth muscle that arteries have?
I know that arterie smooth muscle is innervated by the nervous system? Is this also true for veins?

 

[schrizto]

Arteries carry blood away from the heart to the rest of the body. Veins carry blood back to the heart. Arteries have thicker walls because they need to withstand more pressure than veins.

 

[juniodude]

i think veins also have valves to prevent backflow.

 

[inaccensa]

What are the structural and functional differences between arteries and veins? Do veins have smooth muscle? If so, is it less than the smooth muscle that arteries have?
I know that arterie smooth muscle is innervated by the nervous system? Is this also true for veins?

I wanted to add that Veins carry blood toward the heart. The pressure in veins is lower than the pressure in the arteries. They actually act as a blood reservior or you can say, it stores blood temporarily. Addtionally, the smooth muscle in veins is less than the amount found in arteries. Remember than Arteries have extensive contractile ability, since they are responsible for maintaining BP. Veins are not as muscular as arteries. They have valves in the extremities to prevent the back flow of blood. Veins have thinner walls. Veins do dilate and constrict, I'd guess they are innervated, but I'd like someone to confirm that.

 

[Hemichordate]

i think veins also have valves to prevent backflow.

Do the valves close when the heart contracts or relaxes?

 

[LiveUninhibited]

An interesting fact is that while most veins carry deoxygenated blood, the four pulmonary veins carry oxygenated blood from the lungs to the left atrium. They are the only ones in the post-fetal human that do this. Similarly, while most arteries carry oxygenated blood, the pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs. Umbilical arteries for the fetus are the only others like this.

http://en.wikipedia.org/wiki/Pulmonary_vein

http://en.wikipedia.org/wiki/Pulmonary_artery

You should also be aware of portal veins:

Although most veins take blood back to the heart, there is an exception. Portal veins carry blood between capillary beds. For example, the hepatic portal vein takes blood from the capillary beds in the digestive tract and transports it to the capillary beds in the liver. The blood is then drained in the gastrointestinal tract and spleen where it is taken up by the hepatic veins and blood is taken back into the heart. Since this is an important function in mammals, damage to the hepatic portal vein can be dangerous. Blood clotting in the hepatic portal vein can cause portal hypertension which results in a decrease of blood fluid to the liver.

http://en.wikipedia.org/wiki/Vein#Function

 

[LiveUninhibited]

Do the valves close when the heart contracts or relaxes?

Those valves don't really "close" so much as they impead backflow more than blood flowing towards the heart.

http://en.wikipedia.org/wiki/Vein#Anatomy

Most veins have one-way flaps called venous valves that prevent blood from flowing back and pooling in the lower extremities due to the effects of gravity. These are infoldings of the tunica intima.

 

[Vihsadas]

An important factoid for MCAT purposes is to know that the veins are more pliable than the arteries. Thus, the arteries generally have higher resistance, because the elastance (not elasticity) of their walls is much higher. In turn, veins have a higher blood capacitance. This allows for two main things:

1) Adequate blood pressure in the arteries to ensure blood flow and nutrient distribution
2) Because the walls of the veins have more give and can expand further, the venous systems becomes a "sink" of sorts so that at any given time, the majority of the blood is located in the veins.
This in turn causes a large volume of blood to pool at the right atrium, maintaining "right atrial pressure". And as Artur guyton proposed, this huge volume of liquid in the superior vena cava and right atrium is what drives cardiac output - Kind of like a huge bathtub of liquid, which will push water out of the drain quicker, than a smaller volume.

 

[Stojan]

Veins and Arteries structure is almost the same. Of course, there are different types of veins and arteries but the main and most important difference is that veins carry blood toward the heart while arteries carry it outward. There are many differences between veins and arteries, the blood pressure, valves, lumen, carrying oxygenated blood or deoxygenated blood, etc.