Arterial Blood Flow and Peripheral Resistance Quiz

Factors Affecting Blood Flow

• Several factors affect resistance to blood flow in arteries, including vessel diameter, blood viscosity, and flow velocity.

Reynold's Number

• The equation for Reynold's number (Re) is: Re = ρUL/μ, where ρ is fluid density, U is mean fluid velocity, L is characteristic length, and μ is fluid viscosity.
• Reynold's number predicts whether flow is laminar or turbulent.

Laminar and Turbulent Flow

• When flow is turbulent, resistance increases.
• Characteristics of laminar flow include smooth, continuous flow with little mixing, and a parabolic velocity profile.

Poiseuille's Law

• Poiseuille's law describes the relationship between pressure, flow rate, and resistance in laminar flow: ΔP = 8QL/πr^4, where ΔP is pressure difference, Q is flow rate, L is length, and r is radius.

Critical Reynold's Number

• The critical value of Reynold's number (Re) is around 2000, above which flow is likely to be turbulent.

Flow and Viscosity

• Flow affects viscosity, with high-flow rates reducing viscosity (non-Newtonian fluids) and low-flow rates increasing it.

LaPlace's Law

• LaPlace's Law states that the tension (T) in a vessel wall is proportional to the distending pressure (P) and the radius (R) of the vessel: T = PR.

Vessel Tension

• Smaller vessels require lower tension to oppose blood pressure.

Regulation of Blood Flow

• Arterioles are responsible for regulating blood flow.
• Mechanisms of regulation include myogenic, metabolic, and neurohumoral mechanisms.
• Autoregulation is responsible for the acute regulation of local blood flow.

Blood Flow Characteristics

• Capillaries are characterized by their thin walls, high surface area, and slow flow velocity.
• The slowest velocity of blood flow occurs in capillaries.

Specialised Flows

• Specialised flows in the body include coronary, cerebral, and placental flows.
• Lymphatic flow is NOT a specialized flow in the body.