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2.7.8Inquiry Process

Tissue Fluid — IB Biology HL Revision Notes & Topical Questions

5 min read 4 parts Lesson 80 of 160

📚 IB Biology HL Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Part 1 of 4Formation

Tissue fluid is the medium through which cells exchange materials with blood.

1
At the arteriole end of a capillary bed, blood pressure is relatively high, because the heart has just pushed blood into narrow vessels.
2
This hydrostatic pressure forces plasma through gaps between the endothelial cells, a process called ultrafiltration.
3
Red blood cells and large plasma proteins are too big to pass and remain in the capillary.
4
The fluid that escapes surrounds the body cells and is called tissue fluid.
5
Tissue fluid contains water, glucose, amino acids, oxygen, ions and hormones, but much less protein than plasma.

Part 2 of 4Exchange and Return

Delivery
  • Delivery Oxygen, glucose and amino acids diffuse from tissue fluid into cells, down their concentration gradients.
Waste removal
  • Waste removal Carbon dioxide and urea diffuse from the cells into tissue fluid, then into the blood.
Venous end
  • Venous end Hydrostatic pressure falls along the capillary,
    • while the water potential of plasma stays low because of proteins,
    • so water returns by osmosis.
Lymphatic system
  • Lymphatic system About a tenth of the fluid does not return directly and drains into lymph vessels that eventually empty into the veins near the heart.
End of capillaryHydrostatic (kPa)Plasma protein effect (kPa)Net movement
Arteriole end4.03.3 inwardFluid leaves (+0.7 kPa)
Venule end1.53.3 inwardFluid returns (−1.8 kPa)

Part 3 of 4Clinical Link

Clinical Link
Oedema
  • Oedema Swelling occurs if too much fluid collects in tissues, for example when blood pressure is high or plasma protein is low.
Plasma proteins
  • Plasma proteins Proteins lower the water potential of plasma, drawing water back into the capillary by osmosis.
Lymph nodes
  • Lymph nodes Nodes along lymph vessels filter the fluid and contain white blood cells that respond to infection.
Illustrative values
  • Illustrative values The pressure figures in the table are example values chosen to show the pattern and are not measurements.

Part 4 of 4Exam Checklist & Tips

2.7.8 – Key Points for the Exam

  • Tissue fluid Fluid derived from plasma that surrounds body cells and exchanges materials with them.
  • Ultrafiltration Filtration under pressure through small gaps, which excludes large molecules.
  • Hydrostatic pressure The pressure exerted by a fluid, here the blood pressure inside capillaries.
  • Oedema Abnormal build-up of tissue fluid.
  • Lymph Tissue fluid that has drained into the lymphatic vessels.

Common Mistakes

  • Stating that tissue fluid contains red blood cells; it does not.
  • Saying that tissue fluid is the same as blood plasma; it has much less protein.
  • Forgetting that osmosis, caused by plasma proteins, returns most of the fluid.
  • Describing the lymphatic system as part of the blood circulation; it is a separate drainage system.

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