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Encyclopedia > Vein

In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The vessels that carry blood away from the heart are known as arteries. The study of veins and diseases of the veins is known as phlebology and is a poorly defined discipline that is being developed through a variety of interdisciplinary scientists rather than having a specific set of specialists. Diagram of the human circulatory system. ... The arterial system The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... The heart and lungs, from an older edition of Grays Anatomy. ... Section of an artery For other uses, see Artery (disambiguation). ...

Cross section of a vein showing a valve which prevents backflow
Cross section of a vein showing a valve which prevents backflow

Contents

Diagram of a cross section of a vein with valves. ...

Function

Veins serve to return blood from organs to the heart. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries, entering the veins filled with cellular waste and carbon dioxide. The de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is then pumped to the pulmonary arteries and eventually lungs. In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation. Systemic circulation is the portion of the cardiovascular system which carries oxygenated blood away from the heart, to the body, and returns oxygen-depleted blood back to the heart. ... In the heart, a ventricle is a chamber which collects blood from an atrium (another heart chamber) and pumps it out of the heart. ... Section of an artery For other uses, see Artery (disambiguation). ... The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... This page is about the muscular organ, the Heart. ... The right ventricle is one of four chambers (two atria and two ventricles) in the human heart. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. ... The pulmonary veins carry oxygen rich blood from the lungs to the left atrium of the heart. ... This page is about the muscular organ, the Heart. ...


The return of blood to the heart is assisted by the action of the skeletal-muscle pump which helps maintain the extremely low blood pressure of the venous system. Skeletal-muscle pump is the pumping effect of skeletal muscle on venous blood flow. ... A sphygmomanometer, a device used for measuring blood pressure. ...


Anatomy

Most veins have one-way valves called venous valves to prevent backflow caused by gravity. They also have a thick collagen outer layer, which helps maintain blood pressure and stop blood pooling. The hollow internal cavity in which the blood flows is called the lumen. Veins are surrounded by helical bands of smooth muscles which help maintain blood flow to the right atrium. The total capacity of the veins is more than sufficient to hold the entire blood volume of the body; this capacity is reduced through the constriction of smooth muscles, minimizing the cross-sectional area (and hence volume) of the individual veins and therefore total venous system. Tropocollagen triple helix. ... A sphygmomanometer, a device used for measuring blood pressure. ... artery anatomy, showing lumen The lumen is the interior of a vessel within the body, such as the small central space in an artery or vein, or any of their relating vessels through which blood flows. ... Cultured Smooth muscle of the aorta. ...


Fainting can be caused by failure of the skeletal-muscular pump. Long periods of standing can result in blood pooling in the legs, with blood pressure too low to ascend to the heart. Neurogenic and Hypovolaemic shock can also cause fainting. In these cases the smooth muscles surrounding the veins become slack and fill with blood, absorbing a large portion of the total blood volume, keeping blood away from the brain and causing unconsciousness. The term Faint redirects here. ... Neurogenic shock is shock caused by hiv aids the sudden loss of the sympathetic nervous system signals to the smooth muscle in vessel walls. ... Shock is a serious medical condition where the tissue perfusion is insufficient to meet the required supply of oxygen and nutrients. ...


Common diseases

Common diseases of the veins include varicose veins (treated through radio-frequency ablation, lasers and vein stripping) and deep vein thrombosis. Vein gymnastics in the barefoot park Dornstetten, Germany. ... Somnoplasty is comprised of the Latin root somnus meaning sleep, and the Greek word plastia meaning molding or formation. ... A LASER (acronym for Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam. ... Vein stripping is a surgical procedure done under general anaesthetic to remove varicose veins. ... Deep-vein thrombosis, also known as deep-venous thrombosis or DVT, is the formation of a blood clot (thrombus) in a deep vein. ...


Notable veins and vein systems

The pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The superior and inferior vena cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively. The pulmonary veins carry oxygen rich blood from the lungs to the left atrium of the heart. ... Superior vena cava - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... This article may be too technical for most readers to understand. ...


A portal venous system is a series of veins or venules that directly connect two capillary beds. Examples of such systems include the hepatic portal vein and hypophyseal portal system. In human anatomy, the portal venous system is the system of veins that drain into the portal vein. ... This article or section does not cite its references or sources. ... The portal vein is a major vein in the human body draining blood from the digestive system and its associated glands. ... The hypophyseal portal system is the system of blood vessels that links the hypothalamus and the anterior pituitary. ...


List of important named veins

The pulmonary veins carry oxygen rich blood from the lungs to the left atrium of the heart. ... The portal vein is a major vein in the human body draining blood from the digestive system and its associated glands. ... Superior vena cava - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... This article may be too technical for most readers to understand. ... Grays Fig. ... Great saphenous vein and its tributaries. ...

Names of important venule systems

In human anatomy, the portal venous system is the system of veins that drain into the portal vein. ... It has been suggested that Pulmonary loop be merged into this article or section. ... In human anatomy, the systemic venous system is the veins that drain into the right atrium without passing through two vascular beds (i. ...

Medical interest

Venous valves prevent reverse blood flow.
Venous valves prevent reverse blood flow.

Veins are used medically as points of access to the blood stream, permitting the withdrawal of blood specimens (venipuncture) for testing purposes, and enabling the infusion of fluid, electrolytes, nutrition, and medications. The latter is called intravenous delivery. It can be done by an injection with a syringe, or by inserting a catheter (a flexible tube). In contrast to arterial blood which is uniform throughout the body, the blood removed from veins for testing can vary in its contents depending on the part of the body the vein drains. In example, blood drained from a working muscle will contain significantly less oxygen and glucose than blood drained from the liver. However the more blood from different veins mixes as it returns to the heart, the more homogeneous it becomes. Image File history File links Venous_valve. ... Image File history File links Venous_valve. ... Venipuncture using a vacutainer. ... An electrolyte is a substance containing free ions which behaves as an electrically conductive medium. ... A syringe consists of a plunger fitted to a tube, called the barrel, which has a small opening on one end. ... Catheter disassembled In medicine, a catheter is a tube that can be inserted into a body cavity duct or vessel. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... The liver is an organ in some animals, including mammals (and therefore humans), birds, and reptiles. ...


If an intravenous catheter has to be inserted, for most purposes this is done into a peripheral vein (a vein near the surface of the skin in the hand or arm, or less desirably, the leg.) Some highly concentrated fluids or irritating medications must flow into the large central veins, which are sometimes used when peripheral access cannot be obtained. Catheters can be threaded into the superior vena cava for these uses: if long term use is thought to be needed, a more permanent access point can be inserted surgically. Human right hand The hands (med. ... In anatomy, an arm is one of the upper limbs of a two-legged animal. ... In common usage, a human leg is the lower limb of the body, extending from the hip to the ankle, and including the thigh, the knee, and the cnemis. ... Superior vena cava - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...


The precise location of veins is much more variable from person to person than that of arteries.


Color

The blood carried by veins is dark red due to its high percentage of CO2 as it returns to the heart (in contrast to the high levels of O2 in arterial blood, which is bright red). Veins appear blue because the subcutaneous fat in the skin absorbs lower-frequency light, permitting only the highly energetic blue wavelengths to penetrate and reflect off human skin. Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... The distribution of the bloodvessels in the skin of the sole of the foot. ...


See also

Look up Vein in
Wiktionary, the free dictionary.

Wikipedia does not have an article with this exact name. ... Wiktionary is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... Peripheral Veins are the veins that are the veins leading back towards the heart from the organs below the stomach and also from the muscles in the arms, hands, legs and feet. ... Deep vein is a term used to describe a vein that is deep in the body. ... Deep-vein thrombosis, also known as deep-venous thrombosis or DVT, is the formation of a blood clot (thrombus) in a deep vein. ... This page may meet Wikipedias criteria for speedy deletion. ... Superficial vein is a term used to describe a vein that is close to the surface of the body. ... Varicose veins are veins on the leg which are large, twisted, and ropelike, and can cause pain, swelling, or itching. ...

External Links


  Results from FactBites:
 
Deep Vein Thrombosis (DVT): Venous Disorders: Merck Manual Home Edition (2103 words)
For example, deep vein thrombosis may develop in people who have had a heart attack and lie in hospital beds for several days without sufficiently moving their legs or in people whose legs and lower body are paralyzed (paraplegics).
When deep vein thrombosis blocks blood flow in a large leg vein, the calf swells and may be painful, tender to the touch, and warm.
Sometimes, a filter (umbrella) is placed inside a large vein between the heart and the area affected by deep vein thrombosis, usually the inferior vena cava, which returns blood to the heart from the lower part of the body.
  More results at FactBites »


 

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