Blood Solutions: Understanding Heterogeneous Mixtures
Blood is a heterogeneous mixture (specifically, a suspension of cells in plasma), not a true solution.
Composition
| Component | % Volume | Classification | Key Functions |
|---|
| Plasma | 55% | Colloidal solution (water + proteins) | Transport medium, clotting factors, immunoglobulins, electrolytes |
| Red blood cells (erythrocytes) | ~45% (hematocrit) | Cellular suspension | O₂/CO₂ transport (hemoglobin) |
| White blood cells (leukocytes) | <1% | Cellular suspension | Immune defense |
| Platelets (thrombocytes) | <1% | Cellular fragments | Hemostasis |
Why Heterogeneous?
- Components are not uniformly distributed at microscopic level—cells settle (sedimentation rate).
- Centrifugation separates layers: plasma, buffy coat (WBCs/platelets), RBCs.
- Non‑Newtonian fluid: viscosity changes with shear rate (cell alignment).
Clinical Relevance
- Hematocrit = packed cell volume; reflects RBC mass.
- Buffy coat examination for leukemia, infection.
- Plasma vs. serum: Plasma = unclotted (fibrinogen present); serum = clotted (fibrinogen removed).
- Transfusion medicine: Component therapy (PRBCs, FFP, platelets, cryo) leverages heterogeneity.
Blood's heterogeneous nature enables its multifunctional roles: transport, defense, hemostasis, and homeostasis.
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