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From Wikipedia, the free encyclopedia

Vein
Venous system en.svg
The main veins in the human body
Vein (retouched).svg
Structure of a vein, which consists of three main layers. The outer layer is connective tissue, called tunica adventitia or tunica externa; a middle layer of smooth muscle called the tunica media, and the inner layer lined with endothelial cells called the tunica intima.
Details
SystemCirculatory system
Identifiers
Latinvena
MeSHD014680
TAA12.0.00.030
A12.3.00.001
FMA50723
Anatomical terminology

Veins are blood vessels that carry blood towards 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.

YouTube Encyclopedic

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Transcription

No doubt about it, your heart is a champion. It electrifies itself, it maintains your blood pressure, it keeps your blood moving, and it’s got like a nice shape you can put some chocolates inside of and give to people you like. But the circulatory system is much, much more than just that pump. Because the heart also needs a network to actually send all that blood through, right? Cue the blood vessels. Although it’s easy to think of them as a glorified plumbing system for your body, that’s not a very good analogy. These aren’t just passive tubes made merely to carry liquid around, like the pipes behind your walls at your home. Blood vessels are actually active, dynamic organs, capable of contracting and expanding as they deliver oxygen and nutrients to cells throughout the body; carry away waste products; and do their part in maintaining that all important blood pressure. You already know about the three major types of blood vessels: the arteries that carry blood away from the heart, the veins that bring it back, and the little capillaries that act as the transfer station between the two. But you’ve also got arterioles -- which are like mini-arteries that branch out into those capillaries -- and venules, the smallest vein components that suck blood back out of the capillaries and merge into the larger veins that head home to the heart. And it’s quite an incredible journey, really. If all your blood vessels could be strung together in a single line, they’d stretch out for 100,000 kilometers! That’s like...if you...and then...carry the two -- that’s like two and a half times around the Earth. And together this extensive network forms a closed system that begins and ends in the heart. That means that all of the five or so liters of blood in your body are contained within it at all times, unless you’re bleeding, which I hope you’re not. If you prick a finger and watch a drop of blood pop up, you know that you’ve nicked a blood vessel, and that blood is leaking out of its closed system. Likewise, if you slam your shin against a corner of the coffee table on your way to the bathroom, and an hour later you see a big nasty bruise forming, then you know you’ve damaged your blood vessels again, because bruising is internal bleeding, usually into loose connective tissue. And, if you’re embarrassed about the piercing shriek that you let out when you bumped your leg, and you start to blush. Well, that’s your blood vessels, too, expanding just to say hello. Blood vessels are another great example of how anatomy and physiology go together like peanut butter and jelly. How they look and what they do go hand in hand. Most of your blood vessels share a similar structure consisting of three layers of tissue surrounding the open space, or lumen, that actually holds the blood. Anatomists call these layers “tunics,” and the innermost section is the tunica intima -- which should be pretty easy to remember because, you know, it has like intimate contact with the lumen. It’s like your circulatory underpants. The cool thing about this layer is that it contains the endothelium, which you may remember is made up of simple squamous epithelium tissue and is continuous with the lining of the heart. These cells form a slick surface that helps the blood move without friction. Surrounding the tunica intima is the middle layer, the tunica media, made of smooth muscle cells and sheets of the protein elastin. That smooth muscle tissue is regulated in part by the nerve fibers of the autonomic nervous system, which can decrease the diameter of the lumen by contracting this middle layer during vasoconstriction, or expand it by relaxing during vasodilation. That right there should tell you that the tunica media plays a key role in blood flow and blood pressure, because the smaller the diameter of the blood vessel, the harder it is for blood to move through it -- kinda like trying to drink milk through a cocktail straw versus a soda straw. And finally, the outermost layer of your blood vessels is the tunica externa. It’s like an overcoat, if that coat were made mostly of loosely woven collagen-fiber. Actually, if your coat happens to be made of leather, it is made of collagen. And like a coat, this outer layer is what protects and reinforces the whole blood vessel. Now the ratio of the thicknesses of three layers varies between blood vessels of different types -- because, guess what?! Yes, form follows function! Let’s take a look. Say you’re gearing up for a big tournament of thumb wrestling, or what has been called the “miniature golf of martial arts.” How does blood move through your systemic circulatory loop, to get from your heart to your champion right thumb-flexing muscle, the flexor pollicis brevis, and back again? Well, you will remember from our lessons on the heart that blood leaves the left ventricle through the aorta -- the biggest and toughest artery in your body, roughly the diameter of a garden hose. The aorta and its major branches are elastic arteries -- they contain more elastin than any other blood vessel type, so they can absorb the large pressure fluctuations as blood leaves the heart. What’s more, that elasticity actually dampens that pressure so that big surges don’t reach the smaller vessels, where they could cause damage. This is really where that whole pipe analogy falls apart. These arteries are really more like a balloons -- they’re pressure reservoirs, able to expand and recoil with every heartbeat. If they were rigid like pipes, they’d eventually leak or burst after being battered by so many waves of pressure. So that blood leaves your aorta, and since it’s headed to your thumb, it travels along the elastic subclavian artery, which gives way to a series of muscular arteries -- in this case, the brachial artery in your upper arm, and the radial artery in the lower arm. Muscular arteries distribute blood to specific body parts, and account for most of your named arteries. They’re less elastic and more muscular. These arteries invest in additional smooth muscle tissue, and proportionally, have the thickest tunica media of any blood vessel. This allows them to contract or relax through vasoconstriction and vasodilation, which we’ve talked about a lot in terms of the nervous system’s stress response. These arteries keep tapering down until they turn into the nearly microscopic arterioles that feed into the smallest of your blood vessels, your tiny, extremely thin-walled capillaries which serve as a sort of exchange or bridge between your arterial and venous systems. They may be little, but your capillaries are where the big, important exchange of materials actually happens. Capillary walls are made of just a single layer of epithelial tissue, which form only the tunic intima, so they’re able to deliver the oxygen and other nutrients in your blood to their cellular destinations through diffusion. The capillaries are also where those cells can dump their carbon dioxide and other waste back into the blood and send it away, through the veins to the lungs and kidneys. But I will come back to that in a second. Unlike arteries and veins, capillaries don’t operate on their own, but rather form interweaving groups called capillary beds. Besides exchanging nutrients and gases, your capillary beds also help regulate blood pressure, and play a role in thermoregulation. Say you’re in the room where you’re, like, practicing thumb calisthenics -- which probably isn’t a thing -- but the room is a little chilly, so the blood feeding your dermis loses a lot of heat to that cold air. Well, smooth muscle forms tiny sphincters -- yeah, you’ve got sphincters everywhere -- around the vessels that lead to each of your capillary beds. When they tighten up, they force blood to bypass some of those capillaries, which means less blood is exposed to the cold, and you lose less heat. If it’s really cold, the smooth muscles around your larger arterioles and muscular arteries -- like that radial artery in your lower arm -- will also squeeze, slowing blood flow to your whole hand. Which is no way to win at thumb wrestling. But it’s one reason why your fingers get all stiff and numb in the cold -- they’re not getting as much warm blood, because your blood vessels are trying to conserve heat. Conversely, if your thumb is working really hard and producing heat from all that exertion, those capillary sphincters relax and open wide, flooding the capillary bed with blood to help disperse heat -- which is part of the reason that you might get red-faced when you’re hot or exercising hard. So anyway, now your thumb muscles have just feasted on a batch of oxygen and glucose served up on a fresh bed of capillary, and they’re ready to take out the trash. The cells send their CO2 and other junk out to the venal end of the capillary exchange where the capillaries unite into venules, and then merge into veins that head back to the heart. Remember that the pressure in these vessels has to be dropping, since fluids always flow from higher to lower pressure. But since the pressure is so low in your veins -- it’s like one 12th of the pressure in your arteries -- there isn’t much pressure gradient left to push the blood back to your heart. So veins require some extra adaptations to keep the blood moving in the right direction. That’s why some of them -- especially veins in the arms and legs that have to work against gravity -- have venous valves that help keep the blood from flowing backward. If those valves leak, or a vein experiences too much pressure, the backflow of blood can stretch and twist the vein, leaving you with varicose veins, or if this happens in another part of the body, hemorrhoids. But, anyway, we’ve gotten pretty far from your thumb at this point. We’ve got a loop to finish here! From the capillaries and venules in your thumb, that low-pressure blood flows from the radial vein to the brachial vein to the subclavian vein, where it dumps into the superior vena cava and settles for a second in the right atria, before dropping into the right ventricle. From there it’s sent to the lungs, where it gets oxygenated, and then comes back into into the left atria, before sliding down into the left ventricle, where it builds up pressure again, and spurts back out into your aorta. It takes about a minute for all the blood in your body to complete that circuit, which means, even if you’re mostly at rest, your hardworking circulatory system moves about 7,500 liters of blood through your heart every day. Just in the time that you’ve been sitting there listening to me, probably about 52 liters has coursed through. So yes. Much like the Internet, your blood vessels are more than just “a series of tubes.” During the time that you’ve been circulating all that blood, you learned about the basic three-layer structure of your blood vessels; how those structures differ slightly in different types of vessels; and you followed the flow of blood from your heart to capillaries in your right thumb, and all the way back to your heart again. If you like Crash Course and you want to help us keep making videos like this, you can go to patreon.com/crashcourse. Also, a big thank you to Matthew Pierce for co-sponsoring this episode of Crash Course Anatomy and Physiology. This episode of Crash Course was filmed in the Doctor Cheryl C. Kinney Crash Course Studio. It was written by Kathleen Yale, edited by Blake de Pastino, and our consultant is Dr. Brandon Jackson. It was directed by Nicholas Jenkins; the editor and script supervisor is Nicole Sweeney; our sound designer is Michael Aranda, and the Graphics team is Thought Cafe.

Contents

Structure

Veins are present throughout the body as tubes that carry blood back to the heart. Veins are classified in a number of ways, including superficial vs. deep, pulmonary vs. systemic, and large vs. small.

  • Superficial veins are those closer to the surface of the body, and have no corresponding arteries.
  • Deep veins are deeper in the body and have corresponding arteries.
  • Perforator veins drain from the superficial to the deep veins.[1] These are usually referred to in the lower limbs and feet.
  • Communicating veins are veins that directly connect superficial veins to deep veins.
  • Pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the heart.
  • Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

Most veins are equipped with valves to prevent blood flowing in the reverse direction.

Veins are translucent, so the color a vein appears from an organism's exterior is determined in large part by the color of venous blood, which is usually dark red as a result of its low oxygen content. Veins appear blue because the subcutaneous fat absorbs low-frequency light, permitting only the highly energetic blue wavelengths to penetrate through to the dark vein and reflect back to the viewer. The colour of a vein can be affected by the characteristics of a person's skin, how much oxygen is being carried in the blood, and how big and deep the vessels are.[2] When a vein is drained of blood and removed from an organism, it appears grey-white.[citation needed]

Venous system

The largest veins in the human body are the venae cavae. These are two large veins which enter the right atrium of the heart from above and below. The superior vena cava carries blood from the arms and head to the right atrium of the heart, while the inferior vena cava carries blood from the legs and abdomen to the heart. The inferior vena cava is retroperitoneal and runs to the right and roughly parallel to the abdominal aorta along the spine. Large veins feed into these two veins, and smaller veins into these. Together this forms the venous system.

Whilst the main veins hold a relatively constant position, the position of veins person to person can display quite a lot of variation.[citation needed]

The pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The superior and inferior venae cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively.

The 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.

The peripheral veins carry blood from the limbs and hands and feet.

Microanatomy

Microscopically, veins have a thick outer layer made of connective tissue, called the tunica externa or tunica adventitia. During procedures requiring venous access such as venipuncture, one may notice a subtle "pop" as the needle penetrates this layer. The middle layer of bands of smooth muscle are called tunica media and are, in general, much thinner than those of arteries, as veins do not function primarily in a contractile manner and are not subject to the high pressures of systole, as arteries are. The interior is lined with endothelial cells called tunica intima. The precise location of veins varies much more from person to person than that of arteries.[3]

Function

Veins serve to return blood from organs to the heart. Veins are also called "capacitance vessels" because most of the blood volume (60%) is contained within veins. 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. After taking up cellular waste and carbon dioxide in capillaries, blood is channeled through vessels that converge with one another to form venules, which continue to converge and form the larger veins. 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 through the pulmonary arteries to the 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.

The return of blood to the heart is assisted by the action of the muscle pump, and by the thoracic pump action of breathing during respiration. Standing or sitting for a prolonged period of time can cause low venous return from venous pooling (vascular) shock. Fainting can occur but usually baroreceptors within the aortic sinuses initiate a baroreflex such that angiotensin II and norepinephrine stimulate vasoconstriction and heart rate increases to return blood flow. Neurogenic and hypovolaemic shock can also cause fainting. In these cases, the smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain and causing unconsciousness. Jet pilots wear pressurized suits to help maintain their venous return and blood pressure.

The arteries are perceived as carrying oxygenated blood to the tissues, while veins carry deoxygenated blood back to the heart. This is true of the systemic circulation, by far the larger of the two circuits of blood in the body, which transports oxygen from the heart to the tissues of the body. However, in pulmonary circulation, the arteries carry deoxygenated blood from the heart to the lungs, and veins return blood from the lungs to the heart. The difference between veins and arteries is their direction of flow (out of the heart by arteries, returning to the heart for veins), not their oxygen content. In addition, deoxygenated blood that is carried from the tissues back to the heart for reoxygenation in the systemic circulation still carries some oxygen, though it is considerably less than that carried by the systemic arteries or pulmonary 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.

Cardiac veins

The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins. These include the great cardiac vein, the middle cardiac vein, the small cardiac vein, the smallest cardiac veins, and the anterior cardiac veins. Coronary veins carry blood with a poor level of oxygen, from the myocardium to the right atrium. Most of the blood of the coronary veins returns through the coronary sinus. The anatomy of the veins of the heart is very variable, but generally it is formed by the following veins: heart veins that go into the coronary sinus: the great cardiac vein, the middle cardiac vein, the small cardiac vein, the posterior vein of the left ventricle, and the vein of Marshall. Heart veins that go directly to the right atrium: the anterior cardiac veins, the smallest cardiac veins (Thebesian veins).[4]

Clinical significance

Diseases

Venous insufficiency

Venous insufficiency is the most common disorder of the venous system, and is usually manifested as spider veins or varicose veins. Several varieties of treatments are used, depending on the patient's particular type and pattern of veins and on the physician's preferences. Treatment can include Endovenous Thermal Ablation using radiofrequency or laser energy, vein stripping, ambulatory phlebectomy, foam sclerotherapy, lasers, or compression.

Postphlebitic syndrome is venous insufficiency that develops following deep vein thrombosis.[5]

Deep vein thrombosis

Deep vein thrombosis is a condition in which a blood clot forms in a deep vein. This is usually the veins of the legs, although it can also occur in the veins of the arms. Immobility, active cancer, obesity, traumatic damage and congenital disorders that make clots more likely are all risk factors for deep vein thrombosis. It can cause the affected limb to swell, and cause pain and an overlying skin rash. In the worst case, a deep vein thrombosis can extend, or a part of a clot can break off and land in the lungs, called pulmonary embolism.

The decision to treat deep vein thrombosis depends on its size, a person's symptoms, and their risk factors. It generally involves anticoagulation to prevents clots or to reduce the size of the clot.

Portal hypertension

The portal veins are found within the abdomen and carry blood through to the liver. Portal hypertension is associated with cirrhosis or disease of the liver, or other conditions such as an obstructing clot (Budd Chiari syndrome) or compression from tumours or tuberculosis lesions. When the pressure increases in the portal veins, a collateral circulation develops, causing visible veins such as oesophageal varices.

Other

Thrombophlebitis is an inflammatory condition of the veins related to blood clots.

Imaging

Video of venous valve in action
Video of venous valve in action

Ultrasound, particularly duplex ultrasound, is a common way that veins can be seen.

Veins of clinical significance

The Batson Venous plexus, or simply Batson's Plexus, runs through the inner vertebral column connecting the thoracic and pelvic veins. These veins get their notoriety from the fact that they are valveless, which is believed to be the reason for metastasis of certain cancers.

The great saphenous vein is the most important superficial vein of the lower limb. First described by the Persian physician Avicenna, this vein derives its name from the word safina, meaning "hidden". This vein is "hidden" in its own fascial compartment in the thigh and exits the fascia only near the knee. Incompetence of this vein is an important cause of varicose veins of lower limbs.

The Thebesian veins within the myocardium of the heart are valveless veins that drain directly into the chambers of the heart. The coronary veins all empty into the coronary sinus which empties into the right atrium.

The dural venous sinuses within the dura mater surrounding the brain receive blood from the brain and also are a point of entry of cerebrospinal fluid from arachnoid villi absorption. Blood eventually enters the internal jugular vein.

Phlebology

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

Phlebology is the medical specialty devoted to the diagnosis and treatment of venous disorders. A medical specialist in phlebology is termed a phlebologist. A related image is called a phlebograph.

The American Medical Association added phlebology to their list of self-designated practice specialties in 2005. In 2007 the American Board of Phlebology (ABPh), subsequently known as the American Board of Venous & Lymphatic Medicine (ABVLM), was established to improve the standards of phlebologists and the quality of their patient care by establishing a certification examination, as well as requiring maintenance of certification. Although As of 2017 not a Member Board of the American Board of Medical Specialties (ABMS), the American Board of Venous & Lymphatic Medicine uses a certification exam based on ABMS standards.

The American Vein and Lymphatic Society (AVLS), formerly the American College of Phlebology (ACP) one of the largest medical societies in the world for physicians and allied health professionals working in the field of phlebology, has 2000 members. The AVLS encourages education and training to improve the standards of medical practitioners and the quality of patient care.

The American Venous Forum (AVF) is a medical society for physicians and allied health professionals dedicated to improving the care of patients with venous and lymphatic disease. The majority of its members manage the entire spectrum of venous and lymphatic diseases – from varicose veins to congenital abnormalities to deep vein thrombosis to chronic venous diseases. Founded in 1987, the AVF encourages research, clinical innovation, hands-on education, data collection and patient outreach.

History

Human anatomical chart of blood vessels, with heart, lungs, liver and kidneys included. Other organs are numbered and arranged around it. Before cutting out the figures on this page, Vesalius suggests that readers glue the page onto parchment and gives instructions on how to assemble the pieces and paste the multilayered figure onto a base "muscle man" illustration. "Epitome", fol.14a. HMD Collection, WZ 240 V575dhZ 1543.
Human anatomical chart of blood vessels, with heart, lungs, liver and kidneys included. Other organs are numbered and arranged around it. Before cutting out the figures on this page, Vesalius suggests that readers glue the page onto parchment and gives instructions on how to assemble the pieces and paste the multilayered figure onto a base "muscle man" illustration. "Epitome", fol.14a. HMD Collection, WZ 240 V575dhZ 1543.

The earliest known writings on the circulatory system are found in the Ebers Papyrus (16th century BCE), an ancient Egyptian medical papyrus containing over 700 prescriptions and remedies, both physical and spiritual. In the papyrus, it acknowledges the connection of the heart to the arteries. The Egyptians thought air came in through the mouth and into the lungs and heart. From the heart, the air travelled to every member through the arteries. Although this concept of the circulatory system is only partially correct, it represents one of the earliest accounts of scientific thought.

In the 6th century BCE, the knowledge of circulation of vital fluids through the body was known to the Ayurvedic physician Sushruta in ancient India.[6] He also seems to have possessed knowledge of the arteries, described as 'channels' by Dwivedi & Dwivedi (2007).[6] The valves of the heart were discovered by a physician of the Hippocratean school around the 4th century BCE. However their function was not properly understood then. Because blood pools in the veins after death, arteries look empty. Ancient anatomists assumed they were filled with air and that they were for transport of air.

The Greek physician, Herophilus, distinguished veins from arteries but thought that the pulse was a property of arteries themselves. Greek anatomist Erasistratus observed that arteries that were cut during life bleed. He ascribed the fact to the phenomenon that air escaping from an artery is replaced with blood that entered by very small vessels between veins and arteries. Thus he apparently postulated capillaries but with reversed flow of blood.[7]

In 2nd century AD Rome, the Greek physician Galen knew that blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions. Growth and energy were derived from venous blood created in the liver from chyle, while arterial blood gave vitality by containing pneuma (air) and originated in the heart. Blood flowed from both creating organs to all parts of the body where it was consumed and there was no return of blood to the heart or liver. The heart did not pump blood around, the heart's motion sucked blood in during diastole and the blood moved by the pulsation of the arteries themselves.

Galen believed that the arterial blood was created by venous blood passing from the left ventricle to the right by passing through 'pores' in the interventricular septum, air passed from the lungs via the pulmonary artery to the left side of the heart. As the arterial blood was created 'sooty' vapors were created and passed to the lungs also via the pulmonary artery to be exhaled.

In 1025, The Canon of Medicine by the Persian physician, Avicenna, "erroneously accepted the Greek notion regarding the existence of a hole in the ventricular septum by which the blood traveled between the ventricles." While also refining Galen's erroneous theory of the pulse, Avicenna provided the first correct explanation of pulsation: "Every beat of the pulse comprises two movements and two pauses. Thus, expansion : pause : contraction : pause. [...] The pulse is a movement in the heart and arteries ... which takes the form of alternate expansion and contraction."[8]

In 1242, the Arabian physician, Ibn al-Nafis, became the first person to accurately describe the process of pulmonary circulation,[9] for which he has been described as the Arab Father of Circulation.[10] Ibn al-Nafis stated in his Commentary on Anatomy in Avicenna's Canon:

"...the blood from the right chamber of the heart must arrive at the left chamber but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people thought or invisible pores as Galen thought. The blood from the right chamber must flow through the vena arteriosa (pulmonary artery) to the lungs, spread through its substances, be mingled there with air, pass through the arteria venosa (pulmonary vein) to reach the left chamber of the heart and there form the vital spirit..."

In addition, Ibn al-Nafis had an insight into what would become a larger theory of the capillary circulation. He stated that "there must be small communications or pores (manafidh in Arabic) between the pulmonary artery and vein," a prediction that preceded the discovery of the capillary system by more than 400 years.[11] Ibn al-Nafis' theory, however, was confined to blood transit in the lungs and did not extend to the entire body.

Michael Servetus was the first European to describe the function of pulmonary circulation, although his achievement was not widely recognized at the time, for a few reasons. He firstly described it in the "Manuscript of Paris"[12][13] (near 1546), but this work was never published. And later he published this description, but in a theological treatise, Christianismi Restitutio, not in a book on medicine. Only three copies of the book survived but these remained hidden for decades, the rest were burned shortly after its publication in 1553 because of persecution of Servetus by religious authorities.

Better known discovery of pulmonary circulation was by Vesalius's successor at Padua, Realdo Colombo, in 1559.

Image of veins from William Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus
Image of veins from William Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus

Finally, William Harvey, a pupil of Hieronymus Fabricius (who had earlier described the valves of the veins without recognizing their function), performed a sequence of experiments, and published Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus in 1628, which "demonstrated that there had to be a direct connection between the venous and arterial systems throughout the body, and not just the lungs. Most importantly, he argued that the beat of the heart produced a continuous circulation of blood through minute connections at the extremities of the body. This is a conceptual leap that was quite different from Ibn al-Nafis' refinement of the anatomy and bloodflow in the heart and lungs."[14] This work, with its essentially correct exposition, slowly convinced the medical world. However, Harvey was not able to identify the capillary system connecting arteries and veins; these were later discovered by Marcello Malpighi in 1661.

In 1956, André Frédéric Cournand, Werner Forssmann and Dickinson W. Richards were awarded the Nobel Prize in Medicine "for their discoveries concerning heart catheterization and pathological changes in the circulatory system."[15] In his Nobel lecture, Forssmann credits Harvey as birthing cardiology with the publication of his book in 1628.[16]

In the 1970s, Diana McSherry developed computer-based systems to create images of the circulatory system and heart without the need for surgery.[17]

See also

References

  1. ^ Albert, consultants Daniel (2012). Dorland's illustrated medical dictionary (32nd ed.). Philadelphia, PA: Saunders/Elsevier. p. 2042. ISBN 978-1-4160-6257-8.
  2. ^ Kienle, Alwin; Lilge, Lothar; Vitkin, I. Alex; Patterson, Michael S.; Wilson, Brian C.; Hibst, Raimund; Steiner, Rudolf (1 March 1996). "Why do veins appear blue? A new look at an old question". Applied Optics. 35 (7): 1151. doi:10.1364/AO.35.001151. PMID 21085227.
  3. ^ Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Alexandra Senckowski; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey: Prentice Hall. ISBN 978-0-13-981176-0.
  4. ^ Adams, Matt; Morgan, Matt A.; et al. "Coronary veins". Radiopaedia.org.
  5. ^ Kahn SR (August 2006). "The post-thrombotic syndrome: progress and pitfalls". British Journal of Haematology. 134 (4): 357–65. doi:10.1111/j.1365-2141.2006.06200.x. PMID 16822286.
  6. ^ a b Dwivedi, Girish & Dwivedi, Shridhar (2007). "History of Medicine: Sushruta – the Clinician – Teacher par Excellence" Archived October 10, 2008, at the Wayback Machine, Indian J Chest Dis Allied Sci Vol.49 pp.243-4, National Informatics Centre (Government of India).
  7. ^ Anatomy – History of anatomy. Scienceclarified.com. Retrieved 2013-09-15.
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Further reading

  • Shoja, M. M.; Tubbs, R. S.; Loukas, M.; Khalili, M.; Alakbarli, F.; Cohen-Gadol, A. A. (2009). "Vasovagal syncope in the Canon of Avicenna: The first mention of carotid artery hypersensitivity". International Journal of Cardiology. 134 (3): 297–301. doi:10.1016/j.ijcard.2009.02.035. PMID 19332359.

External links

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