 | Vein: Encyclopedia - Vein
Vein
For the geological use, see vein (geology).
In biology, a vein is a blood vessel which returns blood from the microvasculature to the heart. Veins form part of the circulatory system. The vessels carrying blood away from the heart are known as arteries.
Vein - Biological Vein
Veins have one-way valves to prevent backflow caused by gravity.
In systemic circulation de-oxygenated blood from the capillary blood vessels is taken by veins to the right part of the heart. Differently, in the pulmonary circulation oxygenated blood from the lungs is taken to the left part of the heart by pulmonary veins. Another special case is portal circulation where the portal vein transports blood rich in products of digestion from the intestines to the liver.
Names of important veins:
- Pulmonary veins
- Portal vein
- Superior vena cava
- Inferior vena cava
- Femoral vein
- Great saphenous vein
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).
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.
The precise location of veins is much more variable from person to person than that of arteries.
Deep vein, Deep vein thrombosis, Superficial vein, Varicose vein
See also
- Deep vein
- Deep vein thrombosis
- Superficial vein
- Varicose vein
Heart - Aorta - Arteries - Arterioles - Capillaries - Venules - Veins - Venae cavae - Pulmonary arteries - Lungs - Pulmonary veins - Blood
Categories: Anatomy | Cardiovascular system | Veins
Other related archivesAnatomy, Aorta, Arteries, Arterioles, Blood, Capillaries, Cardiovascular system, Deep vein, Deep vein thrombosis, Femoral vein, Great saphenous vein, Heart, Inferior vena cava, Lungs, Portal vein, Pulmonary veins, Pulmonary arteries, Pulmonary veins, Superficial vein, Superior vena cava, Varicose vein, Veins, Venae cavae, Venules, arm, arteries, biology, blood, blood vessel, capillary, catheter, circulatory system, electrolytes, hand, heart, intestines, leg, liver, lungs, oxygenated, portal circulation, portal vein, pulmonary circulation, pulmonary veins, syringe, systemic circulation, vein (geology), venipuncture
 Adapted from the Wikipedia article "Vein", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki |
