# Explain how the lymphatic system contributes to the maintenance of fluid balance in body tissues.

> IB DP Biology Higher Level (2023 syllabus) — B3.2 Transport · Explain · 4 marks

## Mark scheme (4 marks)

1. Fluid (tissue fluid / interstitial fluid) leaks out of capillaries due to hydrostatic pressure exceeding osmotic pressure at the arteriolar end
2. Not all of the fluid that leaves capillaries is reabsorbed back into the blood at the venular end (approximately 10% remains in tissues)
3. Excess interstitial fluid enters blind-ended lymph capillaries, forming lymph
4. Lymph is eventually returned to the blood (via the thoracic duct / subclavian veins), preventing oedema

## Key terms

- [lymphatic system](https://www.gradenine.co.uk/glossary/lymphatic-system)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-lymphatic-system-contributes-766c03c0) · Published by Druglandscape Ltd.