Why are valves present in veins but not in arteries?
830868
To help bring the blood back against gravity.
480429
A pulmonary vein is called a vein only because it brings blood back to the heart.  However, the blood that it transports back to the heart is oxygenated (contains oxygen).  All other veins carry deoxygenated blood (blood without oxygen).  The pulmonary veins as well as the pulmonary arteries are special because they carry different types of blood then the typical vein or artery.  For another example, the pulmonary artery carries deoxygenated blood.  Arteries carry oxygenated blood, however, this particular artery (the pulmonary artery) carries deoxygenated blood because it is moving from the heart to the lungs so as to get oxygen from the lungs.  Then the blood will travel back through the pulmonary veins (with oxygen in it--oxygenated).  So as you can see, the name of the pulmonary veins and pulmonary arteries has a lot to do with whether it brings blood back to the heart (veins do this) or it takes it away from the heart and out to the body (arteries do this).  If you try not to focus on what type of blood it is (oxygenated or deoxgenated) you may get confused less.  The pulmonary veins and pulmonary arteries can be confusing if you think about what type of blood they're carrying.  They are the exceptions to the typical vein or artery.
248075
Yep. This is very common. The valves in your veins (say your legs) help push the blood back up your legs to your heart. By the time the blood gets to the bottom of your legs, there isnt enough pressure to push it back up, and thats why the valves are there. When they breakdown, the blood cant get pushed up as accurately, and it will pool up, causing you veins to buldge and be permanently damaged. Its pretty common, but can be pretty ugly to look out.\n\nGood luck and hope this helped!
42377
Larger sized veins require less blood pressure to move blood, and therefore put less strain on the heart.\n\nThey probably have healthier hearts, yes, but also their hearts are under less stress than the average person.
560165
mainly, the heart pumps blood forward, but can be aided by the action of the muscles--they help keep blood and lymph flowing.  Additonailly, the veins have one way valves so that once the blood goes through a valve, it can't go backwards while the heart is relaxing.
584848
I've got help for you! There is a vitamin called "Horse Chestnut."  No, it's not made from horses, it comes from a plant with that name. Anyway, it been shown to help diminish varicose veins and promote circulation. Do a search online and you can read more about it what it does, and you can also order it.
1038780
The inside walls of veins have valves that open and close in response to the blood flow. When the left ventricle of the heart pushes blood out into the aorta, it produces the high pressure pulse of the heartbeat and pushes blood throughout the body. Between heartbeats, there is a period of low blood pressure. During this period blood in the veins is affected by gravity and wants to flow downward. The valves in the veins prevent this from happening. Varicose veins start when one or more valves fail to close. The blood pressure in that section of vein increases, causing additional valves to fail. This allows blood to pool and stretch the veins, further weakening the walls of the veins. The walls of the affected veins lose their elasticity in response to increased blood pressure.\nAs the vessels weaken, more and more valves are unable to close properly. The veins become larger and wider over time and begin to appear as lumpy, winding chains underneath the skin. Varicosities can also develop in the deep veins.\nThere is no cure for varicose veins. Treatment falls into two classes: relief of symptoms and removal of the affected veins. Symptom relief includes such measures as wearing support stockings, which compress the veins and hold them in place. This pressure keeps the veins from stretching and limits pain. Other measures include sitting down, using a footstool to support the feet when sitting, avoid standing for long periods of time, and raising the legs whenever possible. These measures work by reducing the blood pressure in leg veins. Prolonged standing allows the blood to collect under high pressure in the varicose veins. Exercise such as walking, biking, and swimming, is beneficial. When the legs are active, the leg muscles help pump the blood in the veins. This limits the amount of blood that collects in the varicose veins and reduces some of the symptoms but does not stop the disease.
249298
All arteries carry oxygenated blood and all veins carry unoxygenated blood except for in the pulmonary circuit, where the pulmonary arteries carry unoxygenated blood from the heart to the lungs, and the pulmonary veins carry oxygenated blood from the lungs back to the heart.
655140
The mitral valve is also known as the bicuspid valve and is found between the ventricles on the left side of the heart.\n\nMitral Valve Prolapse occurs when abnormalities in the mitral valve leaflets, chordae tendinae, or papillary muscles allow prolapse of the mitral valve leaflets backward into the LA during ventricular systole.\n\n• Abnormal mitral valve mechanism which results in billowing of one or both mitral leaflets into the left atrium towards the end of systole.\no  also known as Barlow’s syndrome, as well as “floppy”  \n   or “billowing” mitral valve.\no  the leaflets become enlarged or thickened, and the \n   chordae tendinae become elongated. these changes allow \n   the valve leaflets to billow upward into the LA during \n   ventricular systole.\no  on auscultation, a mid-systolic click is heard\n\nMitral valve prolapse symptoms\n• Most patients: None\n• Chest pain\n• Palpitations\n• Easy fatigability\n• Arrhythmias\n• TIA\n• MR\no mitral valve prolapse pt’s have artherosclerotic problems\n\n\nabove is a little more info compliments of my Medical Surgical notes
45424
In Vericosity a vein is elongated, dilated and tortuous.  sites: Superficial veins of the lower limbs,Veins at the lower end of the gut immediately down the Pharynx (oesophagus) ,In anal canal (piles), and in the spermatic cord (  inside Scrotum) The varicose veins at the gut and the anal canal will bleed.
695395
The volume of blood flowing through the arteries is about the same as that flowing through the veins. It must be since it is a closed circulatory system. \nThe difference is in the internal diameter (lumen) of the vessels. The arteries have smaller lumen and more muscular structure, the veins have less muscle, are of less defined, larger lumen shape. Therefore blood flows slower in the veins, faster in the arteries, but the volume of blood is the same.
233892
I know that Nautilus shells don't have a heart, instead their valves in their arteries and veins that push their blood throughout their system
589435
It is indeed the tricuspid valve. It is one of the Atrioventricular valves named so because of the location between the Atria of the heart and the ventricles. The tricuspid valve is the valve between the right atria and the right ventricle. Its job is to prevent blood flow from the right ventricle back into the right atrium, when the right ventricle is contracting. In your case there is some blood making its way backwards into the right atrium, this is not normal. It means that your valve has some degree of incompetence, Likely you have a murmur. If it is not large your doctor may just decide to leave it alone, if it gets worse or it is large now then the only fix is to have a valve replacement. The good news is that the current valve technology is excellent.
914046
the veins sticking out in normal areas means your veins are healthy and promoting good ciculation, but if theyre sticking out on your head,face,neck it could mean you have either a blockage such as an embolus or cholestorol build up, or your stress and blood pressure level is abnormally high, if so get this check immediately
1044130
It has to do with the fact that the blood coming from veins in order to get to the heart, it has to fight gravity; this is done with the help of valves –i.e. the leg valves http://sln.fi.edu/biosci/vessels/veins.html  .Therefore, the blood coming from them [veins] do not flow as easy as the one coming from the arteries –which flows out from the aorta to the rest of the body with the full force provided by the strong pumping action of the heart. That’s why there is no need to use a vacuum for arterial blood collection.
204353
I thought I answered this question already\n\nThe above two are wrong, because this has nothing to do with physics.... Pressure is higher in the arms because the arms are closer to the heart and lungs. Pressure is highest closer to the heart because the heart pumps the blood.\n\nAlso, there is the factor that oxygen is in the blood. Blood is oxygenated at the lungs. Blood has the highest pressure when it is fully oxygenated, closer to the lungs and in arteries. It has less pressure in capellaries and least in veins. It has less pressure further aweay from the heart and lungs in conclusion.
894662
Well break the words down. Capillaries are closer to the surface of the skin, that is where gases exchange and where waste is disposed of. Veins are a little deeper and have more pressure on them, they are returning blood back to the heart.\nSee you have arteries, veins, and capillaries.\nThe arteries are the pipes going out of the heart, they have the most pressure on them. Because they have to deliver all the blood with the o2 in it to the capillaries all over your body. After the gas exchange at the capillary level, it then turns in to your veins, that return to the heart.