1. Lymphatic System
Dr. Rob Anderson

2. Lymphatic System – General Function
The lymphatic system collects interstitial fluid from tissues and puts this fluid back into the blood
Along with fluids, pathogens and other substances drain into the lymph ducts
White blood cells also reside in the ducts to neutralize pathogens and other foreign materials

3. Components of the Lymphatic System
Lymphatic Vessels – carries and disperses lymph throughout the body as it leaves/ reenters the blood
Lymph (fluid) – essentially blood plasma that has left the blood vessels and become interstitial fluid.
Lymph Nodes – a “battleground” for germs leaving tissues and white blood cells

4. Fluid Dispersion
The fluid that collects in lymph vessels is from interstitial fluid (plasma) leaking out of blood vessels into tissues
The amount of this fluid needs to be balanced, otherwise edema can occur
How do the lymph vessels collect fluid rapidly enough to distribute fluid evenly throughout the body under all conditions?

5. Lymphatic Capillaries
Permeate all tissue (capillary) beds in loose connective tissue (e.g. areolar tissue)
Endothelial cells making up lymph vessels are very loosely connected and attached to surrounding tissue
Loose connections (minivalves) allow fluid to rush in
Collagen connections open minivalves when tissue is under high fluid pressure
What would cause high fluid pressure in tissue beds?

6. Minivalves Open during periods of: Inflammation Infection Hypertension
Large openings allow entry for large proteins and pathogens associated with infections

7. Lymph Circulation (Micro)

8. Lymph Circulation (Body)
Lymph vessels merge into 2 major ducts
Right duct – collects lymph from right side of thorax, right arm and right side of head
Throracic duct – collects lymph from rest of body
All lymph rejoins the blood via these ducts at the right and left jugular veins

9. Lymph Movement
How does lymph move through vessels with no heart to pump it?
Muscular pump
Gravity
What if the flow of lymph gets blocked?

10. Lymphatic Filariasis

11. Lymphoid Cells Immune cells are housed in the lymph tissues
B – Lymphocytes – make antibodies
T – Lymphocytes – directly kill invading organisms or infected cells
Dendritic Cells – phagocytize cells
These cells are often housed in lymph nodes
Lymph carries cell debris, germs and antigens to these cells to “educate” the immune system in what antibodies/B cells to produce

12. Lymph Nodes Act as lymph “filters”
Lymph and infection debris (cell fragments, germs, etc.) are destroyed here by white blood cells
During an infection, lymph nodes can swell as they fill with these substances
NOT swollen GLANDS!

13. Bubonic Plague
Yersinia pestis – bacterial infection carried by rate and rat fleas that killed hundreds of millions of people throughout history
Characterized by “buboes” - hugely swollen lymph nodes in the inguinal, cervical and axillary regions

14. Spleen Located just lateral to greater curvature of the stomach
The spleen synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody-coated blood cells by way of blood and lymph node circulation

15. Tonsils Lymphoid tissues of the upper pharynx
Upper (superficial) tissues made of M cells which capture pathogens and antigens and alert T and B cells deeper in the tissue