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Within Analogies

How Plumbing Comparisons Misrepresent Blood Circulation

Using pipes as an analogy for blood flow can mislead learners about vessel flexibility and pressure dynamics.

On this page

  • Common pipe blood misconceptions
  • Structural limits of the analogy
  • Alternative teaching strategies
Preview for How Plumbing Comparisons Misrepresent Blood Circulation

Introduction

One of the most common ways biology teachers introduce blood flow and pressure is by comparing the circulatory system to household plumbing — pipes carrying water under pressure from a tap or pump. At first glance this seems helpful: both involve fluid moving through connected conduits under pressure. But research in education and cognitive science shows that analogies like this can unintentionally create persistent misconceptions about how blood actually moves through the body. These misunderstandings arise because key features of plumbing don’t map neatly onto the dynamics of flexible, pulsatile blood vessels, and learners often extend the pipe metaphor beyond its explanatory limits. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008

Plumbing Analogy illustration 1

Common Pipe‑Blood Misconceptions

When students hear that “blood flows like water in pipes,” several simplistic inferences can take hold:

  • Rigid conduit assumption: In plumbing, pipes are rigid. Learners may implicitly assume blood vessels behave the same way, overlooking the fact that arteries and veins expand and recoil as part of normal circulation. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008
  • Pressure misconception: Household water systems usually maintain a fairly stable pressure. In contrast, blood pressure varies with each heartbeat and along the vascular network. Learners may misattribute constant pressure analogues to a system that is inherently pulsatile and dynamic. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008
  • Oversimplified resistance view: Plumbing analogies tend to emphasise simple frictional resistance due to pipe diameter narrowing. While vessel radius does affect flow, vascular compliance and inertia — properties absent in rigid pipes — also contribute importantly to overall impedance in the circulatory system. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008

Cognitive researchers describe these as indirectly misleading properties: aspects of the source domain (rigid pipes) that carry over incorrectly into the target domain (circulation) because learners fail to differentiate which features align and which don’t. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008

How blood pressure works - Wilfred Manzano

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Structural Limits of the Analogy

Analogy works when structure mapping — the shared relationships between source and target — is strong. But the plumbing‑circulation comparison breaks down in several key mechanisms:

  • Material flexibility: Unlike household pipes, blood vessels are elastic and regulated by smooth muscle tone. Their ability to stretch and recoil underlies fundamental circulatory functions such as maintaining pressure during diastole, something a rigid pipe analogy fails to capture. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008
  • Pulsatility: Water drawn from a tap flows with a relatively constant head; arterial blood flow is driven by the heart’s rhythmic pumping, with rapid acceleration and deceleration of blood that affect pressure and flow relations. This pulsatility introduces additional components of vascular impedance — compliant and inertial reactance — that have no simple counterpart in household plumbing. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008
  • Dynamic regulation: Blood vessels actively change diameter via smooth muscle contraction in response to metabolic and neural signals. A tap doesn’t self‑regulate in this way, so students may miss how physiological feedback shapes flow distribution in the body. [journals.physiology.org]journals.physiology.orgAnalogies in science and science teachingAnalogies are often used in science, but students may not appreciate their significance, and so…

Because the analogy’s base domain (plumbing) lacks these dynamic features, learners can omit or distort critical aspects of circulatory physics when they overapply the metaphor. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008

Plumbing Analogy illustration 2

Alternative Teaching Strategies

Given the limitations of the plumbing metaphor, educators and researchers recommend alternatives that preserve intuitive appeal while highlighting differences:

  • Explicitly outline limitations: When introducing any analogy, teachers should mark where the comparison breaks down. For circulatory analogies, this means pointing out vessel elasticity and pulsatile pressure as contrasts to rigid pipes. [journals.physiology.org]journals.physiology.orgAnalogies in science and science teachingAnalogies are often used in science, but students may not appreciate their significance, and so…
  • Use multiple analogies: Research on conceptual learning suggests that presenting several analogical comparisons — each capturing different relational features — helps learners build a more complete, nuanced model and reduces the risk of entrenched misconceptions from a single source analogy. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008
  • Structured comparisons: Pair the familiar domain with clear mapping exercises that show which features correspond and which do not. This supports cognitive structure mapping and encourages learners to attend to deeper relationships rather than surface similarities. [Wikipedia]WikipediaStructure-mapping theoryStructure-mapping theory
  • Dynamic simulations and models: Where possible, interactive models that demonstrate pulsatile flow and vessel compliance can provide concrete experiences that contrast with static pipe behaviour, helping students reconcile metaphor with physiological reality. [journals.physiology.org]journals.physiology.orgAnalogies in science and science teachingAnalogies are often used in science, but students may not appreciate their significance, and so…

By combining analogies with clear conceptual boundaries and multiple representational resources, teachers can preserve the pedagogical benefits of analogy while reducing the risk of ingrained misconceptions. [journals.physiology.org]journals.physiology.orgAnalogies in science and science teachingAnalogies are often used in science, but students may not appreciate their significance, and so…

Blood Pressure, Blood Flow, Resistance and Their Relationship|| Hemodynamics

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The Heart, Part 1 - Under Pressure: Crash Course Anatomy & Physiology #25

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Evidence From Educational Research

Studies in science education emphasise that analogies are a double‑edged sword: they can aid initial understanding but also embed incorrect ideas when learners don’t recognise limits. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008 Evidence shows that students often latch onto the most salient features of the analogy while overlooking nuanced aspects of the target domain, a pattern that is particularly clear in the rigid‑pipe analogy for blood flow. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008 Pedagogical interventions that integrate multiple analogies or bridging analogies (metaphors that progressively converge on the scientific concept) have been found more effective at mitigating such misconceptions. [repository.lboro.ac.uk]repository.lboro.ac.ukOvercoming misconceptions: using bridging analogies to…by A Nelmes · Cited by 1 — This research looks at the use of bridging analogies…

In summary, while plumbing metaphors make aspects of blood circulation familiar, their structural differences from vascular physiology can foster persistent misconceptions about flow, pressure dynamics, and vessel behaviour. Thoughtful teaching that situates analogies within a broader set of explanatory tools helps learners construct more accurate mental models. [ResearchGate]researchgate.netResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp…Published: March 28, 2008

Plumbing Analogy illustration 3

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Endnotes

  1. Source: researchgate.net
    Link: https://www.researchgate.net/profile/Rand-Spiro/publication/49176526_Multiple_analogies_for_complex_concepts_antidotes_for_analogy-induced_misconception_in_advanced_knowledge_acquisition/links/543290bb0cf225bddcc7bb24/Multiple-analogies-for-complex-concepts-antidotes-for-analogy-induced-misconception-in-advanced-knowledge-acquisition.pdf
    Source snippet

    ResearchGateMultiple analogies for complex conceptsMarch 28, 2008 — EXAMPLE: A common analogy used to teach opposition to blood flow (imp...

    Published: March 28, 2008

  2. Source: journals.physiology.org
    Link: https://journals.physiology.org/doi/full/10.1152/advan.00022.2010?doi=10.1152%2Fadvan.00022.2010

  3. Source: Wikipedia
    Title: Structure-mapping theory
    Link: https://en.wikipedia.org/wiki/Structure-mapping_theory

  4. Source: repository.lboro.ac.uk
    Link: https://repository.lboro.ac.uk/articles/thesis/Overcoming_misconceptions_using_bridging_analogies_to_cue_scientific_ideas/9357515
    Source snippet

    Overcoming misconceptions: using bridging analogies to...by A Nelmes · Cited by 1 — This research looks at the use of bridging analogies...

  5. Source: teachmephysiology.com
    Title: Blood Flow in Vessels
    Link: https://teachmephysiology.com/cardiovascular-system/circulation/blood-flow-in-vessels/picture-1-5/
    Source snippet

    Circulation - TeachMePhysiologyBLOOD FLOW IN VESSELS Written by Georgie Banks and Kaitlyn Whitelaw BLOOD FLOW IN VESSELS - PODCAST VERSIO...

Additional References

  1. Source: nature.com
    Title: A novel tube law analysis under anisotropic external load | Scientific Reports
    Link: https://www.nature.com/articles/s41598-024-82476-7
    Source snippet

    December 17, 2024 — A novel tube law analysis under anisotropic external load Download PDF Download PDF * Article * Open access *...

    Published: December 17, 2024

  2. Source: macstandl.com
    Link: https://macstandl.com/analogies-and-multiple-explanations/
    Source snippet

    Analogies and Multiple ExplanationsResources, ideas and prompts for discussion related to Explanation. Making complex ideas easier to und...

  3. Source: en12.zlibrary.to
    Link: https://en12.zlibrary.to/dl/multiple-analogies-for-complex-concepts-antidotes-for-analogy-induced-misconception-in
    Source snippet

    PDFSeptember 1, 1988 — Since the analogy-based misconceptions involve very technical subject matter, our characterizations will stress th...

    Published: September 1, 1988

  4. Source: uakron.edu
    Link: https://www.uakron.edu/polymer/agpa-k12outreach/best-teaching-practices/using-analogies
    Source snippet

    using analogiesUsing analogies assists in concept development. This is particularly true when students have alternative conceptions about...

  5. Source: my.chartered.college
    Link: https://my.chartered.college/impact_article/misconceptions-p-prims-and-bridging-analogies-in-physics-teaching/
    Source snippet

    chartered.collegeMisconceptions, p-prims and bridging analogies in Physics...by G Jones — The 'misconceptions' we are talking about are...

  6. Source: studyres.com
    Title: Multiple analogies for complex concepts: antidotes for analogysource
    Link: https://studyres.com/doc/13513537/multiple-analogies-for-complex-concepts—antidotes-for-a
    Source snippet

    EXAMPLE: A common analogy used to teach opposition to blood flow (impedance) uses rigid pipe systems such as household plumbing as the so...

  7. Source: sciencedirect.com
    Title: Hemodynamics of vascular ‘waterfall’: is the analogy justified?
    Link: https://www.sciencedirect.com/science/article/abs/pii/003456879290060A
    Source snippet

    ScienceDirectRESPIRATION PHYSIOLOGY Volume 87, Issue 2, February 1992, Pages 205-217 Respiration Physiolo… HEMODYNAMICS OF VASCULAR ‘WATE...

    Published: February 1992

  8. Source: sciencedirect.com
    Title: Hemodynamics of vascular ‘waterfall’: is the analogy justified?
    Link: https://www.sciencedirect.com/science/article/pii/003456879290060A
    Source snippet

    ScienceDirectRESPIRATION PHYSIOLOGY Volume 87, Issue 2, February 1992, Pages 205-217 Respiration Physiolo… HEMODYNAMICS OF VASCULAR ‘WATE...

    Published: February 1992

  9. Source: boldscience.org
    Title: How can analogies promote learning?
    Link: https://boldscience.org/how-can-analogies-promote-learning/
    Source snippet

    BOLD11 Aug 2022 — Analogies can increase comprehension and reduce misconceptions. They may be particularly helpful for learning about con...

  10. Source: research.cuhk.edu.hk
    Title: cuhk.edu.hk Teachers’ misconceptions of the circulatory system
    Link: https://research.cuhk.edu.hk/en/publications/teachers-misconceptions-of-the-circulatory-system-2/
    Source snippet

    cuhk.edu.hkTeachers' misconceptions of the circulatory system - The Chinese University of Hong KongTEACHERS' MISCONCEPTIONS OF THE CIRCUL...

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