In the circulatory system, a vein is a blood vessel that carries blood back toward the heart (as opposed to artery, a blood vessel carrying blood away from the heart). This is an article about the rock music band "Circulatory System" The blood vessels are part of the Circulatory system and function to transport Blood throughout the body Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic Arteries are Blood vessels that carry blood away from the Heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood. The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. The umbilical vein is a Blood vessel present during fetal development that carries Oxygenated Blood from the Placenta to the growing Fetus

Contents 1 Anatomy 1.1 Venous tone 2 Function 3 Medical interest 4 Common diseases 5 Deep vein thrombosis 6 Phlebology 7 Notable veins and vein systems 8 Colour 9 Types of veins 10 See also 11 References 12 External links 12.1 Scientific publications

Anatomy

Veins function to return deoxygenated blood to the heart, and are essentially tubes that collapse when their lumens are not filled with blood. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic A lumen (Lat lūmen, an opening or light (pl lumina is the inside space or lining of a tubular structure such as an artery or intestine The thick, outer-most layer of a vein is made of collagen, wrapped in bands of smooth muscle while the interior is lined with endothelial cells called intima. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the 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. Gravitation is a natural Phenomenon by which objects with Mass attract one another The precise location of veins is much more variable from person to person than that of arteries. Arteries are Blood vessels that carry blood away from the Heart. ^[1]

Venous tone

Main article: Vasovagal syncope

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 venous tone of the smooth muscles, minimizing the cross-sectional area (and hence volume) of the individual veins and therefore total venous system. The helical bands of smooth muscles which wrap around veins help maintain blood flow to the right atrium. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder In cases of vasovagal syncope, the smooth muscles relax and the veins of the extremities below the heart fill up with blood, failing to return sufficient volume to maintain cardiac output and blood flow to the brain. Cardiac output (Q is the volume of blood being pumped by the Heart, in particular by a ventricle in a minute The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain

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. Systemic circulation is the portion of the Cardiovascular system which carries Oxygenated Blood away from the heart to the Body, and returns The left ventricle is one of four chambers (two atria and two ventricles in the Human Heart. Arteries are Blood vessels that carry blood away from the Heart. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 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. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The right atrium (in older texts termed the "right auricle" is one of four chambers (two atria and two ventricles in the Human The right ventricle is one of four chambers (two atria and two ventricles in the Human Heart. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive 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. Pulmonary circulation is the portion of the Cardiovascular system which carries Oxygen -depleted Blood away from the heart to the Lungs, and The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. The left atrium is one of the four chambers in the Human 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. The skeletal-muscle pump is a collection of Skeletal muscles that aid the Heart in the circulation of Blood. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories 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 return blood to the heart. Neurogenic and hypovolaemic shock can also cause fainting. Neurogenic shock is shock caused by the sudden loss of the Autonomic nervous system signals to the Smooth muscle in vessel walls 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.

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 systemic circulation still carries some oxygen, though it is considerably less than that carried by the systemic arteries or pulmonary veins.

In a functional analogy, the term "venous" in economics refers to recycling industries, in contrast to "arterial" or production industries. Economics is the social science that studies the production distribution, and consumption of goods and services. Recycling involves processing used materials into new products in order to prevent the waste of potentially useful materials reduce the consumption of fresh raw materials reduce

Medical interest

Veins are used medically as points of access to the blood stream, permitting the withdrawal of blood specimens (venipuncture) for testing purposes, and intravenous delivery of fluid, electrolytes, nutrition, and medications through injection with a syringe, or by inserting a catheter. In medicine venipuncture or venepuncture (also known as phlebotomy, venesection, blood draw, drawing blood or taking blood Intravenous therapy or IV therapy is the giving of Liquid substances directly into a Vein. An electrolyte is any substance containing free Ions that behaves as an electrically conductive medium A syringe is a simple piston Pump consisting of a plunger that fits tightly in a tube In Medicine a catheter is a tube that can be inserted into a body cavity duct or vessel 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; blood drained from a working muscle will contain significantly less oxygen and glucose than blood drained from the liver. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. The liver is a vital organ in the human body and is present in Vertebrates and some other animals However the more blood from different veins mixes as it returns to the heart, the more homogeneous it becomes.

If an intravenous catheter has to be inserted, for most purposes this is done into a peripheral vein near the surface of the skin in the hand or arm, or less desirably, the leg. The hands ( med / lat: manus pl manūs are the two intricate prehensile multi- Fingered body parts normally located at the end of each arm of a In Anatomy, an arm is one of the Upper limbs of an animal The term arm can also be used for analogous structures such as one of the paired upper limbs In common usage the human leg is the lower limb of the Body, extending from the Hip to the Ankle, and including the Thigh, the 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. The superior vena cava is a large yet short Vein that carries deoxygenated Blood from the upper half of the body to the Heart 's Right atrium

Common diseases

The most common vein disorder is venous insufficiency, usually manifested by spider veins or varicose veins. Telangiectasias are small dilated Blood vessels near the surface of the skin or Mucous membranes measuring between 0 Varicose veins are Veins that have become enlarged and twisted A variety of treatments are used depending on the patient's particular type and pattern of veins and on the physician's preferences. Treatment can include radio-frequency ablation, vein stripping, ambulatory phlebectomy, foam sclerotherapy, lasers or compression. Somnoplasty is comprised of the Latin root somnus meaning sleep and the Greek word plastia meaning molding or formation Vein stripping is a surgical procedure done under General anaesthetic to remove Varicose veins. Ambulatory phlebectomy is a treatment for superficial Varicose veins. Sclerotherapy is a procedure used to treat Blood vessels or blood vessel malformations (vascular malformations and also those of the Lymphatic system. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission.

Deep vein thrombosis

Main article: Deep vein thrombosis

Deep vein thrombosis is a condition where a blood clot forms in a deep vein, which can lead to pulmonary embolism and chronic venous insufficiency. In Medicine, deep vein thrombosis (also known as deep-vein thrombosis or deep venous thrombosis and usually abbreviated as DVT) is the formation A thrombus, or blood clot, is the final product of the Blood coagulation step in Hemostasis. Pulmonary embolism (PE is a blockage of the Pulmonary artery or one of its branches usually occurring when a venous Thrombus (blood clot from a vein

Phlebology

Phlebology is the medical discipline that involves the diagnosis and treatment of disorders of venous origin. Diagnostic techniques used include the history and physical examination, venous imaging techniques and laboratory evaluation related to venous thromboembolism. Thrombosis is the formation of a blood Clot ( Thrombus) inside a Blood vessel, obstructing the flow of Blood through the Circulatory The American Medical Association has added phlebology to their list of Self-Designated Practice Specialties. The American College of Phlebology is a professional organization of physicians and health care professionals from a variety of backgrounds. Annual meetings are conducted to facilitate learning and sharing of knowledge regarding venous disease. The equivalent body for countries in the Pacific is the Australasian College of Phlebology, active in Australia and New Zealand.

Notable veins and vein systems

The Greater Saphenous vein (GSV) is the most important superficial vein of the lower limb. First described by the Persian physician Avicenna, Saphenous derives its name from Safina, meaning hidden. This vein is 'hidden' in its own fascial compartment in the thigh and only exits the fascia near the knee. Incompetence of this vein is an important cause of varicose veins of lower limbs.

The pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. The superior and inferior venae cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively. The superior vena cava is a large yet short Vein that carries deoxygenated Blood from the upper half of the body to the Heart 's Right atrium The inferior vena cava (or IVC is the large Vein that carries de-oxygenated Blood from the lower half of the body into the Heart.

A portal venous system is a series of veins or venules that directly connect two capillary beds. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Examples of such systems include the hepatic portal vein and hypophyseal portal system. The hepatic portal vein (often portal vein for short is a Portal vein in the human body that drains blood from the Digestive system and its associated The hypophyseal portal system (or hypothalamo-hypophyseal portal system) is the system of Blood vessels that links the Hypothalamus and the Anterior

Colour

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). Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Veins appear blue because the subcutaneous fat in the skin absorbs lower-frequency light, permitting only the highly energetic blue wavelengths to penetrate through to the dark vein and reflect off. The subcutaneous tissue or subcutis is the layer of Loose connective tissue directly underlying the Dermis. This physical effect can also be seen in the iris of blue eyes (pigmentless iris in the front, dark retina in the back) and is called Rayleigh scattering. The iris consists of Pigmented Fibrovascular tissue known as a stroma. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Rayleigh scattering (named after Lord Rayleigh) is the elastic Scattering of Light or other electromagnetic radiation by particles much smaller

Types of veins

Veins can be classified into:

• portal vein vs. non-portal (most common)
• superficial veins vs. Superficial vein is a term used to describe a Vein that is close to the surface of the body deep veins
• pulmonary veins vs. Deep vein is a term used to describe a Vein that is deep in the body The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. systemic veins

List of important named veins

• Jugular veins
• Pulmonary veins
• Portal vein
• Superior vena cava
• Inferior vena cava
• Iliac vein
• Femoral vein
• Popliteal vein
• Great saphenous vein
• Small saphenous vein

Names of important venule systems

• Portal venous system
• Systemic venous system

See also

• Peripheral vein
• Deep vein
• Deep vein thrombosis
• Superficial vein
• Varicose veins
• Pulmonary circulation

References

External links

• Merck Manual article on veins.
• American College of Phlebology
• American Board of Phlebology
• American College of Phlebology Foundation
• In economics: Arterial and venous industries
• Animated Venous Access tutorials

Scientific publications

• Phlebology - international journal of venous diseases
• Phlebology: The Journal of Venous Disease

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