Vascular Function, Capillary Exchange and Oedema
Key concepts on resistance, compliance, Starling forces and oedema formation in the peripheral circulation.
Keyboard Shortcuts
💡 Pro tip: Use keyboard shortcuts for faster studying!
Study Smart Tips for Vascular Function, Capillary Exchange and Oedema
Master these concepts using proven study techniques that actually work:
Active Recall
Test yourself before flipping each card to strengthen memory retention
Spaced Repetition
Review difficult cards more frequently than easy ones
Multiple Sessions
Break study time into shorter, focused sessions
Explain Aloud
Verbalize answers to reinforce understanding
Questions Covered in This Set
10 cards to master
Poiseuille's law for resistance
R = 8ηL / (πr⁴) — resistance is inversely proportional to the fourth power of radius, so halving radius increases resistance 16-fold.
Why are arterioles the main resistance vessels?
They have thick smooth muscle relative to a tiny lumen, so small radius changes cause huge resistance changes (r⁴ effect), controlling tissue perfusion and TPR.
Definition of compliance and typical arterial vs venous values
C = ΔV/ΔP. Arteries ≈ 2 mL/mmHg (low compliance); veins ≈ 100 mL/mmHg (~20–24× more compliant), holding 65–70% of blood volume.
What is the Windkessel effect?
Elastic aorta stores blood in systole and recoils in diastole, converting pulsatile ejection into near-continuous capillary flow. Pulse pressure ≈ stroke volume ÷ arterial compliance.
Why does ageing cause isolated systolic hypertension?
Reduced arterial compliance means the same stroke volume produces a larger pulse pressure: systolic BP rises, diastolic falls.
State the Starling equation
Jv = Kf [(Pc − Pi) − σ(πc − πi)], where Kf is the filtration coefficient and σ the reflection coefficient.
List the four Starling pressures and their directions
Pc (~32→15 mmHg) pushes fluid out; Pi (−2 to 0 mmHg) pulls slightly out; πc (25–28 mmHg, mainly albumin) pulls in; πi (3–8 mmHg) pulls out.
Net filtration at arteriolar vs venular end (muscle capillary)
Arteriolar: (32 + 1 + 5) − 28 = +10 mmHg outward (filtration). Venular: (15 + 1 + 5) − 28 = −7 mmHg (reabsorption).
What does the reflection coefficient σ represent?
How effectively the capillary wall excludes protein: σ ≈ 1 in tight brain capillaries, ~0.5 in leaky hepatic sinusoids.
How do series and parallel resistances combine?
Series: R_total = R₁ + R₂ + … ; Parallel: 1/R_total = Σ1/Rᵢ. Many parallel organ beds lower TPR — muscle vasodilation in exercise drops TPR sharply.
