3 Fluids in Biological Systems Free Online FlashCards

What drives fluid through a pathway?

A pressure difference drives fluid flow; pressure alone does not determine flow.

How does tube radius affect ideal laminar resistance?

For ideal laminar flow in a cylindrical tube, $R=\frac{8\eta L}{\pi r^4}$: resistance rises with viscosity and length, and falls sharply as radius increases.

How do resistances combine in series?

For pathways in series, total resistance is the sum of their individual resistances.

What does conservation of volume require at a flow branch?

At a branch, incoming flow equals the sum of outgoing flows: $Q_{\mathrm{in}}=\sum Q_{\mathrm{out}}$.

How do arterioles regulate blood flow to organs?

Arteriolar smooth muscle changes vessel radius, altering resistance and helping regulate blood flow to organs.

What pressure change draws air into the lungs during inhalation?

During inhalation, chest expansion lowers pressure in the lungs relative to atmospheric pressure, drawing air inward.

What does lung compliance measure?

Compliance is the change in lung volume divided by the change in pressure: $C=\frac{\Delta V}{\Delta P}$. It describes ease of expansion.

How do hydrostatic and oncotic forces affect capillary filtration?

Hydrostatic pressure tends to push fluid away from the higher-pressure compartment, while plasma proteins create oncotic force that opposes filtration from blood.

How are flow rate, pressure drop, and resistance related?

Flow rate is pressure drop divided by resistance: $Q=\frac{\Delta P}{R}$.

What happens to ideal tube flow if its radius doubles?

Doubling the radius increases ideal flow sixteenfold at the same pressure difference, because flow is proportional to $r^4$.

What happens to total resistance when pathways are added in parallel?

Parallel pathways lower total resistance below that of any single branch; adding branches can increase total flow.

Why is average blood speed relatively low in capillaries?

The many capillaries create a large total cross-sectional area, so average blood speed is relatively low and exchange has more time to occur.