Pressure and flow in arteries and veins

Question 1

What is systolic pressure?

Answer 1

The maximum arterial pressure during ventricular systole (contraction).

Question 2

What is diastolic pressure?

Answer 2

The minimum arterial pressure during ventricular diastole (relaxation).

Question 3

What is pulse pressure, and how is it calculated?

Answer 3

Pulse pressure is the difference between systolic and diastolic pressure:
Pulse Pressure = Systolic Pressure – Diastolic Pressure

Question 4

What are the Korotkoff sounds, and how are they used?

Answer 4

Korotkoff sounds are turbulent blood flow sounds heard when measuring blood pressure with a sphygmomanometer:

First sound = Systolic pressure (blood starts flowing through compressed artery).
Last sound disappears = Diastolic pressure (unrestricted laminar flow resumes).

Question 5

How does the aortic pressure wave change as it moves through the vascular tree?

Answer 5

Large arteries: High-pressure, pulsatile flow.

Arterioles: Greatest drop in pressure (high resistance).

Capillaries: Low pressure, no pulsatility (steady flow).

Veins: Lowest pressure, aiding venous return.

Question 6

How does blood velocity change across the vasculature?

Answer 6

Highest in arteries, due to smaller total cross-sectional area.

Lowest in capillaries, due to largest total cross-sectional area (allows nutrient exchange).

Increases in veins, but never reaches arterial velocity.

Question 7

What factors affect pressure and flow in veins?

Answer 7

Gravity – Can slow or aid venous return.

Muscle pump – Skeletal muscle contraction helps push blood toward the heart.

Respiratory pump – Inhalation decreases thoracic pressure, pulling venous blood upward.

Venous valves – Prevent backflow, ensuring unidirectional flow.

Sympathetic stimulation – Increases venous tone, reducing capacitance and aiding return

Question 8

What mechanisms prevent blood clotting in vessels?

Answer 8

Endothelial cells – Produce nitric oxide (NO) and prostacyclin, which inhibit platelet aggregation.

Heparan sulfate – Enhances antithrombin III, inhibiting clotting factors.

Thrombomodulin – Activates protein C, which degrades clotting factors V and VIII.

Fibrinolytic system – Plasmin breaks down fibrin clots.