1. Lesson objectives To describe the structure of the lymphatic system
To explain how the lymphatic system works
To identify the main lymph nodes of the body

2. Structure of Lymphatic System
Lymphatic capillaries
Lymphatic vessels
Lymph nodes
Lymphatic ducts

3. Lymphatic capillaries
Structure: fine, blunt-ended permeable tubes, composed of a single layer of thin cells

4. Lymphatic vessels
Structure: thin-walled, collapsible vessels similar to veins but carrying lymph not blood

5. Lymph nodes
Structure: each node is made of lymphatic tissue, surrounded by a wall of tough, white fibrous tissue

6. Right lymphatic duct
Empties into right subclavian vein to rejoin circulatory system
Function: receives all drained lymph from right side of head, chest and neck and from right arm

7. Thoracic duct
Empties into subclavian vein to rejoin circulatory system
Function: collects and drains lymph from left side of head, the neck, both lower limbs, left side of trunk and left arm

8. What is the lymphatic system?
Lymphatic system is a secondary circulation, helping blood circulation carry out its functions
Blood travels to and from the tissues delivering nutrients and removing waste
Whole blood never leaves capillaries but leucocytes, oxygen, food and water can

9. What is the lymphatic system?
Once outside the capillaries they are carried by a derivative of blood plasma called tissue/interstitial fluid
This fluid circulates throughout the tissues, delivering food, oxygen and water to cells and collecting carbon dioxide
When it has finished its work not all of it can pass through capillary walls because the pressure is too high

10. What is the lymphatic system?
Fluid that is left is picked up by the lymphatic capillaries
These have larger pores in their walls than blood capillaries and the pressure inside is lower
Excess tissue fluid and substances made of large molecules etc. drain away into them
The fluid – called lymph – is filtered by lymph nodes then collected by the lymphatic ducts before entering right/left subclavian veins and returning to the bloodstream

11. Connection between blood and lymph

12. Simplified lymph circuit

13. Structure: plasma, lymphocytes, proteins and waste products
Lymph – Structure
Structure: plasma, lymphocytes, proteins and waste products

14. Functions of Lymphatic System
Transports fat
Controls swelling
Fights infection

15. Effect of Lymphatic System on Skin and Muscles
Removes waste and toxins from skin and muscles so they can work more efficiently

16. Movement of lymph
Contraction of skeletal muscles collapses vessels and because valves are present, lymph is directed towards the upper part of body
There is a slight oncoming pressure from tissue fluids
Movement of lymph towards thorax during inspiration
Negative suction pressure helps pull lymph upwards

17. Structure of lymph node

18. Functions of lymph nodes
Filter lymph, remove and destroy harmful micro-organisms, tumour cells, damaged or dead tissue cells; filtering system prevents toxic materials from reaching bloodstream and causing septicaemia
Produce new lymphocytes and antibodies
Lymphatic tissue cells within node may become activated to form antibodies against a particular infection

19. Main lymphatic ducts

20. Lymphatic nodes – head and neck
Superficial parotid nodes – in front of ears
Mastoid nodes – behind ears
Submandibular – beneath mandible
Occipital nodes – base of skull
Deep cervical nodes – deep within neck
Superficial cervical nodes – side of neck

21. Lymphatic nodes – body Axillary nodes – armpit
Supratrochlear nodes – elbow crease
Iliac nodes – abdomen
Inguinal nodes – groin
Popliteal nodes – knee

22. Lies on upper left-hand side of abdomen
Spleen
Lies on upper left-hand side of abdomen

23. Spleen – Functions 1. Forms new lymphocytes
2. Destroys thrombocytes and erythrocytes
3. Helps fight infection

24. Tonsils

25. Tonsils Lymphoid tissue that plays role in immune function
Tonsils help to fight infection

26. Main Lymphatic Nodes