Regulation of Blood Flow and Pressure

Key Concepts

• Hydrostatic Pressure: All fluids exert hydrostatic pressure.
• Blood Pressure: The hydrostatic force that blood exerts against vessel walls, propelling blood through the vascular system.

Blood Flow Pathway

1. Aorta: Carries blood away from the left ventricle.
2. Arteries: Branch from the aorta.
3. Arterioles: Smaller branches of arteries.
4. Capillaries: Networks fed by arterioles.
5. Venules: Merge from capillaries.
6. Veins: Merge into vena cava.
7. Vena Cava: Superior and inferior vena cava return blood to the right atrium.

Blood Pressure Fluctuations

• Arteries: Blood pressure ranges from 110 mmHg (systolic) to 75 mmHg (diastolic).
• Arterioles to Veins: Pressure decreases to 0 mmHg.

Mechanisms Promoting Venous Return

1. Skeletal Muscle Contractions: Push blood when veins' valves are closed.
2. Respiratory Inspiration: Creates pressure gradient aiding blood return.

Variables Influencing Blood Pressure

• Stroke Volume: Blood volume ejected per heart contraction.
• Heart Rate: Beats per minute.
• Cardiac Output: Stroke volume x heart rate.
• Peripheral Resistance: Opposes blood pressure.

Peripheral Resistance Factors

• Total Cross-sectional Area: Cumulative area of all vessels.
• Luminal Diameter: Size of vessel opening.

Blood Flow Velocity

• Aorta and Arteries: Highest velocity.
• Capillaries: Lowest velocity, optimized for exchange.
• Veins and Vena Cava: Lower velocity than initial arteries.

Adjusting Peripheral Resistance

• Vasoconstriction: Reduces diameter, increases resistance.
• Vasodilation: Increases diameter, decreases resistance.

Clinical Correlation: Sphygmomanometer

• Measures blood pressure using:
  • Inflatable Cuff: Closes artery.
  • Stethoscope Detection: Identifies systolic and diastolic pressure.
• Blood Pressure Measurement: Recorded as systolic over diastolic pressure.

This concludes the overview of blood flow and pressure regulation.