Test how an unchanged organ responds to a shared supply constraint

1. Define the structure and boundary

Tissue identification describes a component, but organ function depends on how components are connected. A supply pathway, exchange surface and downstream demand can jointly constrain performance. Two organs connected to a shared supply do not behave like two isolated containers with independently fixed inputs. A local change can alter another organ’s boundary conditions without changing that organ’s tissue structure.

2. Connect anatomical evidence and mechanism

The original circuit uses a maintained pressure difference of 12, a shared upstream resistance Rs, then parallel organ branches A and B. Branch B resistance is fixed at 4. Parallel branches share their pressure difference, not their flow. Their equivalent resistance is Rp=4 RA/(4+RA); total flow is 12/(Rs+Rp), branch pressure is total flow times Rp, and each branch flow divides that pressure by its own resistance.

Lowering A resistance can raise total flow while lowering the pressure available to both branches, because the larger total flow causes a larger shared upstream drop. Branch B flow can therefore fall even though its resistance is unchanged. This is a causal boundary example, not a prediction for a particular body: actual circulation is pulsatile and actively regulated, and tissue responses can change the supplied resistances.

Use the module’s evidence types together. A real micrograph supports selected structural features; a compartment ledger constrains material redistribution; a feedback trace constrains a controller; and a network model constrains coupled flows. None substitutes for the others. Preserve an original explanation, identify which observations could reject it and distinguish guided image/model practice from supervised anatomical practicals or independently reviewed learner reasoning.

3. Audit an original worked comparison

With Rs=2 and RA=2, Rp=4/3, total flow=3.6 and branch pressure=4.8. A flow is 2.4 and B flow 1.2. Lowering RA to 1 gives Rp=0.8, total flow=30/7, pressure=24/7 and B flow=6/7: B flow falls although its resistance remains 4.

4. Predict and investigate

Predict first: Can an organ with unchanged resistance receive less flow when a neighboring branch becomes easier to perfuse?

Hold shared resistance at 2 and compare A resistance 2 versus 1. Check flow conservation and both pressure drops. State what independent measurement would distinguish a changed B resistance from a changed shared supply pressure.

5. Transfer to a changed case

Apply the mechanism to a changed boundary

At Rs=1 and RA=4, calculate equivalent branch resistance, total flow and each organ flow.

Retain the first response, units, uncertainty and any prior feedback exposure in the notebook before comparing this public explanation.

Compare a worked response

Equal branches give Rp=2; total flow=12/3=4, branch pressure=8 and each branch flow=2. The shared drop is 4 and total pressure drop remains 12.

6. Retain an evidence-based defense

Use the Anatomy and Physiology course workspace to preserve original reasoning, actual image observations with uncertainty, model settings and a reviewer-supplied new transfer. Public feedback is guided practice, not independent mastery or clinical assessment. No examination, personal health data, specimen collection or physiological challenge is requested.

Supporting anatomical mechanism, checked 30 October 2026. Numerical packets and diagrams are original teaching models; actual tissue images have separate attribution, download and CC0 provenance records.