Relation To Wall Tension
Regardless of site, blood pressure is related to the wall tension of the vessel according to the Young–Laplace equation (assuming that the thickness of the vessel wall is very small as compared to the diameter of the lumen):
where
- P is the blood pressure
- t is the wall thickness
- r is the inside radius of the cylinder.
- is the cylinder stress or "hoop stress".
For the thin-walled assumption to be valid the vessel must have a wall thickness of no more than about one-tenth (often cited as one twentieth) of its radius.
The cylinder stress, in turn, is the average force exerted circumferentially (perpendicular both to the axis and to the radius of the object) in the cylinder wall, and can be described as:
where:
- F is the force exerted circumferentially on an area of the cylinder wall that has the following two lengths as sides:
- t is the radial thickness of the cylinder
- l is the axial length of the cylinder
Read more about this topic: Blood Pressure
Famous quotes containing the words relation to, relation, wall and/or tension:
“Hesitation increases in relation to risk in equal proportion to age.”
—Ernest Hemingway (1899–1961)
“Our sympathy is cold to the relation of distant misery.”
—Edward Gibbon (1737–1794)
“A man whose mind feels that it is captive would prefer to blind himself to the fact. But if he hates falsehood, he will not do so; and in that case he will have to suffer a lot. He will beat his head against the wall until he faints. He will come to again and look with terror at the wall, until one day he begins afresh to beat his head against it; and once again he will faint. And so on endlessly and without hope. One day he will wake up on the other side of the wall.”
—Simone Weil (1909–1943)
“The prevalence of suicide, without doubt, is a test of height in civilization; it means that the population is winding up its nervous and intellectual system to the utmost point of tension and that sometimes it snaps.”
—Havelock Ellis (1859–1939)