Revision Notes

9.5 The Lymphatic System

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Lymph Fluid

  • The walls of the capillaries are so thin that water, dissolved solutes and dissolved gases easily leak out of them / pass through the walls from the plasma into the tissue fluid surrounding the cells
  • Cells exchange materials (such as water, oxygen, glucose, carbon dioxide, mineral ions) across their cell membranes with the tissue fluid surrounding them by diffusion, osmosis or active transport
  • More fluid leaks out of the capillaries than is returned to them, and this excess of leaked fluid surrounding the capillaries then passes into the lymphatic system, becoming lymph fluid


How lymph forms, IGCSE & GCSE Biology revision notesHow lymph forms

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Lymph Vessels & Nodes

  • The lymphatic system is formed from a series of tubes which flow from tissues back to the heart
  • It connects with the blood system near to the heart, where lymph fluid is returned to the blood plasma
  • Lymph nodes are small clusters of lymphatic tissue found throughout the lymphatic system, especially in the neck and armpits
  • Large numbers of lymphocytes are found in lymph nodes
  • Tissues associated with the lymphatic system, such as bone marrow, produce these lymphocytes
  • Lymphocytes play an important role in defending the body against infection

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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