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. The precise location of veins is much more variable from person to person than that of arteries. Veins often display a lot of anatomical variation compared with arteries within a species and between species.
Read more about this topic: Vein
Famous quotes containing the word anatomy:
“Man is a shrewd inventor, and is ever taking the hint of a new machine from his own structure, adapting some secret of his own anatomy in iron, wood, and leather, to some required function in the work of the world.”
—Ralph Waldo Emerson (1803–1882)
“I love to see, when leaves depart,
The clear anatomy arrive,”
—Roy Campbell (1902–1957)
“But a man must keep an eye on his servants, if he would not have them rule him. Man is a shrewd inventor, and is ever taking the hint of a new machine from his own structure, adapting some secret of his own anatomy in iron, wood, and leather, to some required function in the work of the world. But it is found that the machine unmans the user. What he gains in making cloth, he loses in general power.”
—Ralph Waldo Emerson (1803–1882)