BMS1031 Wk1L1 Flashcards

Introduction to Fluid Physics

• Bodies consist of about 55-60% water.

• Heart pumps 8,000 liters of blood daily.

• Importance of fluid flow in physiology and medicine.

Fluid Circulation in the Body

• Blood circulation involves deoxygenated blood being pumped from the heart to lungs for reoxygenation, returning to the heart to flow to capillaries in tissues.

• The cycle repeats as deoxygenated blood returns to the heart.

Learning Outcomes

• Understand fundamental fluid concepts (density, pressure).

• Learn about pressure properties: Pascal's principle, hydrostatic pressure, and fluid pressure measurement.

Basic Concepts of Fluid Dynamics

• Pressure Difference Drives Fluid Flow:

  • Flow occurs from high pressure areas to low pressure areas.

  • No flow without pressure drop; resistance affects flow rate.

  • Relationship: Flow rate (Q) = Pressure Difference / Resistance.

Flow and Electric Circuits Analogy

• Fluid flow compared to electrical circuits:

  • Pump generates pressure difference (like a battery creates voltage).

  • Fluid flow through resistive elements compared to current through resistors (Ohm's Law analogy).

Definitions of Fluid

• Fluids include liquids and gases that can change shape to fit their container.

• Density: Mass per unit volume (ρ = mass/volume).

  • SI unit: kilograms per cubic meter (kg/m³).

Pressure in Fluids

• Pressure defined as force (F) applied over area (A):

  • P = F / A

  • SI unit: Pascal (Pa), where 1 Pa = 1 N/m².

• Example: Small force applied over a small area can generate significant pressure.

Hydrostatic Pressure

• Hydrostatic pressure involves pressure in a stationary fluid.

• Pressure increases with depth due to weight of overlying fluid:

  • Hydrostatic Pressure (P) = ρgh, where ρ = density, g = gravity (9.8 m/s²), h = height of fluid.

• Example: At 2m deep in water, pressure is approximately 19,600 Pa.

Pascal’s Principle

• States that if an external pressure is applied to a confined fluid, the pressure increases uniformly throughout.

• Shows how pressure is the same at every point within a stationary fluid.

Measuring Pressure

• Atmospheric Pressure: Pressure of the atmosphere at sea level (~101.3 kPa).

• Gauge Pressure: Difference between the pressure of a system and atmospheric pressure.

  • Commonly used in blood pressure and tire gauges.

Manometer for Pressure Measurement

• Open tube manometer: A device measuring pressure differences via a fluid column height change due to pressure imbalances.

• Uses mercury due to its density, often reported in millimeters of mercury (mmHg).

Blood Pressure Measurement

• Sphygmomanometer: Device to measure blood pressure.

  • Measures systolic (pressure during heartbeat) and diastolic (pressure between beats).

  • Blood pressure expressed in mmHg (e.g., 120/80).

Summary of Fluid Properties in Physiology

• Importance of understanding fluid dynamics, density, and pressure for understanding cardiovascular health and functioning.

• Next lectures will delve deeper into fluid flow and its implications in physiology.