This lecture covers Womersley's theory for pulsatile flow, focusing on the use of harmonics to describe arterial pulses, the solution for pressure gradients, the definition of the Womersley parameter, and the relationship between flow and pressure gradient. It also discusses the physical meaning of the Womersley parameter in the context of Navier-Stokes equations and the viscous layer thickness. The presentation concludes with insights into pulsatile flow profiles and measurements.