1. Lymphatic System Questions List the organs and structures of the lymphatic system? What are the two functions of the lymphatic system? Why does there need to be a system that collects interstitial fluid and deliver that fluid into blood vessels? What is the function of a lymph node? What is lymphatic tissue? How is lymphatic tissue different than a lymph node? What is the function of the thymus gland? What is the function of white pulp and red pulp in the spleen?

2. Lymphatic system

3. Lymph System Two Basic Functions of Lymph System 1.To return excess interstitial fluid to blood flow –Also transports absorbed lipids from GI tract 2.Monitor body for pathogens and other harmful substances (often by filtering lymph) i.e., immune function/initiation of immune response

4. Lymphatic System Synopsis: The lymphatic system consists of a series vessels that collect and transport fluid. It also contains structures involved with immune response During the process of transporting fluid the lymphatic system screens for harmful substances/pathogens and can initiate an immune response Some organs of the lymph system are involved with development of white blood cells and the removal of old red blood cells

5. Lymphatic Vessels/Conductive Structures Lymph nodes Lymphatic tissue/lymph nodules (e.g., MALT, tonsils) Spleen Thymus Major Structures of the Lymphatic System

6. Filtration, Interstitial Fluid, and Lymph The fluid within blood vessels is plasma. 1.Within capillaries the process of filtration results in a net (i.e., overall) loss of fluid from blood vessels. 2.This fluid exits capillaries and enters the spaces between cells –The fluid is now called interstitial fluid 3.As interstitial fluid builds up/accumulates its pressure increases and it is “pushed” into lymphatic vessels 4.Once the fluid enters a lymphatic vessel it is called lymph. 5.Lymph is transported through the body and lymph vessels combine lymph with blood so you do not lose blood volume due to filtration in step 1 above

7. Fig. 13.37 Net loss of fluid (3.6L/day) from capillaries results in fluid flow: –Plasma  –interstitial space/fluid  –lymph  –plasma “ flushes interstitial fluid enhancing immune system function Keeps interstitial fluid and plasma in “communication” Increases distribution of materials especially insoluble lipids that have difficulty crossing capillary walls

8. Summary: Fluid lost from capillaries washes over cells and enters the lymphatic system where is it passed through lymph nodes before being recombined with blood.

9. How lymph moves Lymph is propelled through lymphatic vessels through a combination of: –Muscle pump: like venous blood, contraction of skeletal muscles compresses lymph vessels and pushed lymph through vessels –Contraction of smooth muscle within lymphatic vessels walls –Compression of lymphatic vessels by pulsile blood flow of adjacent arteries Lymphatic vessels have valves (like veins) to ensure lymph travels in one direction (toward its reunification with blood)

10. Detection of pathogens by lymph nodes Lymph is passed through lymph nodes which are “filters” containing white blood cells that can detect and remove pathogens and initiate an immune response.

11. Figure 24.10 Lymph Nodes: Up to 1” in size, they are surrounded by a dense connective tissue capsule and contain macrophages and lymphocytes that can detect pathogens and initiate immune response if necessary

12. The Lymph System includes Lymphatic Tissue that also had a pathogen detection and immune function Lymphatic Tissues include: Tonsils Lymph nodules in the intestines White pulp in spleen Lymphatic tissue is simply a structure rich with lymphocytes and macrophages that detect pathogens and initiate an immune response. They are like lymph nodes that are not surrounded by a capsule and are not connected to lymphatic vessels

14. Additional Lymph System Organs include: Spleen Thymus Gland

15. Spleen Within the spleen there are two types of material/tissue 1. Red Pulp (main function) –Removal of old RBC’s by macrophages 2. White pulp –lymphatic in function as in lymphatic tissue Spleen

16. Thymus Gland T-Lymphocytes finish there development in the thymus gland Large and active while young By age 40 most of it has been replaced by adipose and CT

17. Additional Lymph Items There is a large amount of variation among individuals in how the lymph ducts/trunks connect to the veins of the thoracic region Blockage of vessels results in fluid build up and swelling/edema Swollen lymph nodes are due to increased number of lymphocytes in nodes responding to infections Metastasized cancer cells are often caught in lymph nodes so lymph nodes are often biopsied in cancer assessments

18. Elephantiasis due to filarial worm infection: (serious) edema as the result of blocked lymph flow