Lecture 8 - Law of Laplace

Question 1

What does the law of Laplace relate?

Answer 1

The law of Laplace relates transmural pressure, Pt, with wall stress, σ, for a wall of thickness h.

Question 2

What is transmural pressure?

Answer 2

For a circular cylinder transmural pressure acts to push two halves apart. Wall stress acts to keep them together.

Question 3

Laplace equation in a circular cylinder and in a sphere?

Answer 3

sigma(cylinder) = Pt *Ri / h

sigma(sphere) = Pt *Ri / 2h

Question 4

How does the body adapt to hypertension in vessels?

Answer 4

Cardiac muscle cells develop thicker cardiac walls leading to concentric hypertrophy

The thicker wall but similar lumen causes wall stress to return to presumably normal levels despite higher pressures in systole.