Blood is a complex fluid with unique properties. While primarily considered a non-Newtonian fluid, it also exhibits characteristics of a viscoelastic fluid.
Understanding Blood's Fluid Properties
Blood isn't simply a liquid; it's a suspension of various cells within a liquid matrix. This gives it properties that differ from simple liquids like water.
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Non-Newtonian: As noted in the Wikipedia article on Hemorheology (https://en.wikipedia.org/wiki/Hemorheology), blood's viscosity changes depending on the shear rate (how quickly it's flowing). At high shear rates (like in large blood vessels), it flows more easily; at low shear rates (small vessels), it's more viscous. This is unlike Newtonian fluids (like water) where viscosity remains constant regardless of flow rate. This characteristic is further supported by information from https://pmc.ncbi.nlm.nih.gov/articles/PMC3614720/ which mentions that while initially considered Newtonian, blood's viscoelasticity is now recognized.
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Viscoelastic: Blood demonstrates both viscous and elastic properties. The viscous part comes from the plasma's viscosity (as described in the provided text snippet), while the elastic component is due to the red blood cells' deformability.
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Composition: The MedlinePlus article (https://medlineplus.gov/blood.html) and a Quora answer (https://www.quora.com/What-type-of-fluid-is-blood) highlight that blood consists of a liquid component (plasma—water, salts, and proteins) and a solid component (blood cells). This complex composition contributes to its unique fluid behavior.
Blood in Different Contexts
Several sources mention blood in various contexts, confirming its classification as a fluid:
- Wound drainage: Serous drainage, or blood serum, is a type of fluid exudate from wounds (https://my.clevelandclinic.org/health/symptoms/25033-serous-drainage).
- Disease diagnosis: Blood and other body fluids are used for diagnostic testing (https://pubmed.ncbi.nlm.nih.gov/2896300/, https://pubmed.ncbi.nlm.nih.gov/36128749/).
- Fluid buildup: Pleural effusion involves fluid, including blood, building up in the lungs (https://cancer.ca/en/treatments/side-effects/fluid-buildup-on-the-lung-pleural-effusion).
