Vein

related topics
{disease, patient, cell}
{@card@, make, design}
{acid, form, water}
{math, energy, light}
{line, north, south}
{rate, high, increase}

In the circulatory system, veins (from the Latin vena) 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. Veins differ from arteries in structure and function; for example, arteries are more muscular than veins, veins contain valves, and arteries carry blood away from the heart.

Contents

Anatomy

In general, veins function to return deoxygenated blood to the heart, and are essentially tubes that collapse when their lumens are not filled with blood. The thick outermost layer of a vein is made of connective tissue, called tunica adventitia or tunica externa. Deeper are bands of smooth muscle called tunica media, which are, in general, thin, as veins do not function primarily in a contractile manner. The interior is lined with endothelial cells called tunica intima. 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. These are infoldings of the tunica intima. The precise location of veins is much more variable from person to person than that of arteries.[1]

Notable veins and vein systems

The greater 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.

Full article ▸

related documents
Porphyria
Ischaemic heart disease
Dementia
Diarrhea
Varicose veins
Monoamine oxidase inhibitor
Headache
Dopamine
Atropine
Dehydroepiandrosterone
Experimental cancer treatment
Infectious mononucleosis
Duesberg hypothesis
Psychopharmacology
Metabolic syndrome
Pelvic inflammatory disease
Temporomandibular joint disorder
Rett syndrome
Bilateral cingulotomy
Anthrax
Pseudoephedrine
Retinol
Tears
Phenylketonuria
Ophthalmology
Charcot-Marie-Tooth disease
Stimulant
Smallpox vaccine
Radiation therapy
Cerebrospinal fluid