Vein

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Veins are one of the five different types of [[blood vessels|blood vessels]] that make up the circulatory system. ([[Arteries|Arteries]], [[Arterioles|Arterioles]], [[Venules|Venules]] and [[Capillaries|Capillaries]] being the others)  
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Veins are one of the five different types of [[Blood vessels|blood vessels]] that make up the circulatory system. ([[Arteries|Arteries]], [[Arterioles|Arterioles]], [[Venules|Venules]] and [[Capillaries|Capillaries]] being the others)  
  
The majority of veins carry [[deoxygenated blood|deoxygenated blood]] to the [[heart|heart]] apart from the [[pulmonary vein|pulmonary vein]] that carries oxygenated blood to the [[heart|heart]]. The walls of veins are made of three layers:  
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The majority of veins carry [[Deoxygenated blood|deoxygenated blood]] to the [[Heart|heart]] apart from the [[Pulmonary vein|pulmonary vein]] that carries oxygenated blood to the [[Heart|heart]]. The walls of veins are made of three layers:  
  
#The ''tunica intima ''consisting of a layer of flat [[endothelial cells|endothelial cells]] overlaying a thin layer of connective tissue.  
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#The ''tunica intima ''consisting of a layer of flat [[Endothelial cells|endothelial cells]] overlaying a thin layer of connective tissue.  
#The ''tunica media '' consisting of circular layer of [[Smooth_muscle|smooth muscle]] containing [[elastin|elastin]] and [[collagen|collagen]]. This provides mechanical strength for the vein.  
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#The ''tunica media '' consisting of circular layer of [[Smooth muscle|smooth muscle]] containing [[Elastin|elastin]] and [[Collagen|collagen]]. This provides mechanical strength for the vein.  
 
#The ''tunica adventitia ''consisting of a layer of elastic and collagenous fibres fixed along the length of the vessel.<strike></strike> <ref>Pocock G.,Richards C.(2006) Human Physiology: The Basis of Medicine, 3rd Edition, Oxford University Press. Chapter 15 - Pg 264</ref>
 
#The ''tunica adventitia ''consisting of a layer of elastic and collagenous fibres fixed along the length of the vessel.<strike></strike> <ref>Pocock G.,Richards C.(2006) Human Physiology: The Basis of Medicine, 3rd Edition, Oxford University Press. Chapter 15 - Pg 264</ref>
  
The blood pressure in veins in very low, compared to the blood pressure in arteries and therefore veins have valves which stop the backflow of blood. Skeletal muscles also help deoxygenated blood in the vein to get back into the heart by squeezing the vein when they contract. Finally, veins branch into venules which join the capillaries in the body.<br>  
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The blood pressure in veins in very low, compared to the blood pressure in arteries and therefore veins have valves which stop the backflow of blood. Skeletal muscles also help deoxygenated blood in the vein to get back into the heart by squeezing the vein when they contract. Finally, veins branch into venules which join the capillaries in the body.<br>
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[[Image:Vein_med.jpg|411x254px]]
  
 
=== References:  ===
 
=== References:  ===
  
 
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Revision as of 00:18, 6 December 2017

Veins are one of the five different types of blood vessels that make up the circulatory system. (Arteries, Arterioles, Venules and Capillaries being the others)

The majority of veins carry deoxygenated blood to the heart apart from the pulmonary vein that carries oxygenated blood to the heart. The walls of veins are made of three layers:

  1. The tunica intima consisting of a layer of flat endothelial cells overlaying a thin layer of connective tissue.
  2. The tunica media  consisting of circular layer of smooth muscle containing elastin and collagen. This provides mechanical strength for the vein.
  3. The tunica adventitia consisting of a layer of elastic and collagenous fibres fixed along the length of the vessel. [1]

The blood pressure in veins in very low, compared to the blood pressure in arteries and therefore veins have valves which stop the backflow of blood. Skeletal muscles also help deoxygenated blood in the vein to get back into the heart by squeezing the vein when they contract. Finally, veins branch into venules which join the capillaries in the body.


Vein med.jpg

References:

  1. Pocock G.,Richards C.(2006) Human Physiology: The Basis of Medicine, 3rd Edition, Oxford University Press. Chapter 15 - Pg 264
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