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:
“The adolescent does not develop her identity and individuality by moving outside her family. She is not triggered by some magic unconscious dynamic whereby she rejects her family in favour of her peers or of a larger society.... She continues to develop in relation to her parents. Her mother continues to have more influence over her than either her father or her friends.”
—Terri Apter (20th century)
“... a worker was seldom so much annoyed by what he got as by what he got in relation to his fellow workers.”
—Mary Barnett Gilson (1877–?)
“I make myself this time
Of wood or granite or lime
A wall too hard for crime
Either to breach or climb....”
—Robert Frost (1874–1963)
“Many people I know in Los Angeles believe that the Sixties ended abruptly on August 9, 1969, ended at the exact moment when word of the murders on Cielo Drive traveled like brushfire through the community, and in a sense this is true. The tension broke that day. The paranoia was fulfilled.”
—Joan Didion (b. 1935)