1. Lymphatic System

2. Functions ► Picks up excess fluids (lymphatic fluid/lymph) from tissues and filters out pathogens ► Returns cleansed fluid back to blood stream ► Able to pick up larger molecules that may not fit into cardiovascular vessels

3. Arrangement ► Lymphatic vessels run throughout the entire body ► They are blind ended vessels that carry fluid only one way ► Lymphatic vessels end at lymphatic capillaries that are deeply embedded in body tissues

4. Lymphatic Capillaries ► Microscopic ► Very porous (more than cardiovascular capillaries) one layer of simple squamous epithelium ► This arrangement allows for larger molecules to be absorbed

5. Holding Chambers ► Two major areas RIGHT LYMPHATIC DUCT RIGHT LYMPHATIC DUCT THORACIC DUCT THORACIC DUCT

6. Right Lymphatic Duct ► Drains lymph from the right upper extremity and right side of head, neck and upper torso

7. Thoracic Duct ► Largest lymphatic vessel ► Drains lymph from remaining three fourts of the body ► Large pouch: cisterna chyli

8. Lacteals ► Specialized larger lymphatic capillaries that are found in the intestinal wall ► Able to pick up fat molecules (extra large molecules)

9. Other parts of lymphatic system ► Lymph nodes ► Thymus gland ► Tonsils ► Spleen

10. Lymph nodes ► Actual filtering stations ► Lymph passest through and nodes trap pathogens ► Nodes may become enlarged when overwhelmed with number of pathogens and white blood cells killing them ► Excess fluid develops; pus ► Also store immature B-cells

11. Structure of a lymph node ► Afferent vessels pick up excess fluid (several) ► Efferent vessel drains lymph node (only one)

12. Location of lymph nodes ► Back of throat ► Neck ► Armpit ► Groin ► Behind knee ► Abdominal wall

13. Tonsils ► Lymph nodes at back of throat ► 3 parts ► Palatine (tonsils ► Pharyngeal (adenoids) ► Lingual ► See page 341

14. Thymus Gland ► Located in mediastinum ► Produces T-cells at an early age ► Makes hormones ► Gets smaller after adolescence ► Replaced by fat ► Process of involution; turns in on itself

15. Spleen ► Largest lymphatic organ ► Located in LUQ ► Fi;ltration of bacteria ► Phagocytes present (large quantities) ► Large rervoir of old RBC’s ► Very rich blood supply ► Removed: splenectomy