How do capillary walls, being 1 endothelial cell thick, sustain 25-30% of the hydrostatic pressure in the lumen of the aorta (~25-30 mmHg in the beginning)?
- Law of Laplace: T = Pr
- T = the vessel wall tension, aka the force needed to expand the vessel, r = cylinder radius, & P = luminal pressure
- at a constant P, increasing radius causes an increase in the wall tension, leading to rupture of the cylinder
- *a capillary can sustain relatively high pressure because its radius is so small (radius is so small that the wall tension isn't that large even though there's a significant amount of pressure)