1-2 April 2015

Lymphatic System Function The lymphatic system consists of two main parts, each with different functions: 1. Lymphatic vessels collect interstitial fluid and return it to the blood vessels 2. Lymphoid organs house immune cells and help protect the body from disease

Lymphatic Capillaries Lymphatic capillaries collect interstitial fluid and dissolved particles, including proteins, cell debris, and pathogens Surround blood capillaries in loose connective tissue Blind-ended (have a true start) Minivalves ensure fluid only goes in one direction – towards heart. Lymphatic capillaries are MUCH more permeable than blood capillaries. Large particles, including pathogens and cancer cells, cannot directly get into blood capillaries but they easily enter lymphatic capillaries

Lymphatic Vessels Lymphatic capillaries join together to form lymphatic vessels. Lymphatic vessels pass through multiple lymph nodes for cleansing Lymphatic vessels empty into the subclavian veins

What makes lymph flow? Pressure differences provide the force Higher pressure of interstitial fluid than of lymph in capillaries starts flow Respiratory and skeletal muscle pumps help maintain flow in lymph vessels Largest lymph vessels have smooth muscle walls that contract rhythmically to push lymph along Valves ensure that flow is unidirectional Minivalves in capillaries ‘true’ valves in large lymph vessels

Think, Pair, Share Compare and contrast blood vessels and lymphatic vessels in terms of structure and function. 5 min

Lymph Nodes House immune cells (phagocytes and lymphocytes) Filter lymph, breaking down cell debris and destroying pathogens and cancer cells There are thousands of lymph nodes scattered throughout the body. Large clusters of lymph nodes occur in cervical (neck), axillary (arm pit), and inguinal (groin) area.

Lymph Nodes When you are sick, your lymph nodes often swell as they collect and fight pathogens.

Other lymphoid organs House immune cells, but do not filter lymph Tonsils: trap and remove pathogens that enter throat Thymus: produces hormones and develops T- lymphocytes Spleen: filters blood, destroys old erythrocytes Peyer’s patches: destroy pathogens in intestines There are other, small patches of lymph tissue throughout body

Closure What was our objectives, and what did we learn? What was our learner profile trait and how did we demonstrate it? How does what we did today tie to our unit question?

Exit Ticket Questions 1 - 6: A = Lymph vessel only, B = Blood vessel only, C = both, D = neither 1. Fluid moves due to heart pump 2. Fluid moves due to respiratory pump 3. Contain valves 4. Make a full loop 5. Contains oxygen and nutrients 6. Permeable to large molecules and small cells

Exit Ticket 7. What functions to cleanse blood and destroy old RBCs? 8. What functions to cleanse lymph? 9. What functions to destroy pathogens in the intestines? 10. What serves as a site for lymphocyte maturation? Extra Credit (3 pts): What are the three regions with clusters of lymph nodes?