Blood is flowing through a circuit with an inflow pressure of 100 mm Hg and an outflow pressure of 10 mm Hg. Each of the parallel circuits (R1, R2, R3, R4 and R5) has a resistance of 5 mm Hg/mL/min. What is the blood flow across this circuit?
**Core Concept**
The question tests the understanding of the resistance and flow relationship in a vascular circuit, specifically in a parallel circuit configuration. The total resistance of parallel circuits is determined by the reciprocal of the sum of the individual resistances.
**Why the Correct Answer is Right**
To find the total resistance of the parallel circuit, we calculate the reciprocal of the sum of the individual resistances. Since each of the parallel circuits (R1, R2, R3, R4, and R5) has a resistance of 5 mm Hg/mL/min, the total resistance (Rt) is calculated as:
1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5
= 1/5 + 1/5 + 1/5 + 1/5 + 1/5
= 1/1 (or 1) mm Hg/mL/min
Therefore, the total resistance of the circuit is 1 mm Hg/mL/min.
Using the formula for flow in a circuit (Q = ΔP/R), where ΔP is the pressure difference and R is the total resistance, we can calculate the blood flow across the circuit:
Q = ΔP/R
= (100 - 10) mm Hg / 1 mm Hg/mL/min
= 90 mm Hg/mL/min
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the parallel circuit configuration.
**Option B:** This option is incorrect because it uses the formula for series circuits instead of parallel circuits.
**Option C:** This option is incorrect because it does not provide the correct calculation for the total resistance of the parallel circuit.
**Clinical Pearl / High-Yield Fact**
In a parallel circuit, the total resistance is determined by the reciprocal of the sum of the individual resistances. This concept is crucial in understanding the hemodynamics of multiple vascular beds and calculating blood flow in complex circulatory systems.
**Correct Answer:**
90 mm Hg/mL/min