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Chapter 22.docx - Chapter 22 Lymphatic System and Immunity...

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Chapter 22: Lymphatic System and Immunity Introduction to Lymphatic System o Pathogen: disease-causing organism o Lymphatic system: cells, tissues & organs responsible for defending the body o Immunity: ability to resist infection & disease o Immune system: include all cells & tissues involved in producing immunity Function of the Lymphatic System o 1) Lymph: Fluid similar to plasma but has lower conc. of suspended proteins. o 2) Lymphatic vessels (lymphatics): Carry lymph from peripheral tissues veins o 3) Lymphoid tissues & lymphoid organs o 4) Lymphoid Cells: Lymphocytes, phagocytes, & other immune system cells Function of the Lymphatic System: produce, maintain & distribute lymphocytes o Lymphocytes are produced: In lymphoid tissues (e.g., tonsils), lymphoid organs (e.g., spleen, thymus), & in red bone marrow o Lymphocyte distribution: Detect problems & travel to site of injury or infection o Lymphocyte Circulation: From blood to IF through capillaries Lymphatic vessels carry lymph from peripheral tissues to veins Lymphatic Vessels: o Are vessels that carry lymph and begins with smallest vessels o 1) Lymphatic capillaries (terminal lymphatics) o 2) Lymphatic collecting vessels o 3) Lymphatic trunks o 4) Lymphatic ducts & then end in venous system; towards the heart 1) Lymphatic Capillaries o Differ from blood capillaries in four ways Closed at one end rather than forming continuous tubes Have larger lumen diameters Have thinner walls Flat or irregular outline in sectional view Have overlap that acts as a 1-way valve: allowing fluids, solutes, viruses & bacteria to enter preventing return to intercellular space Does not have a basement membrane Has anchoring filaments Can drain fluid unless there is too much pressure o Lacteals: intestinal capillaries that transport lipids absorbed by digestive tract 2) Large Lymphatic collecting Vessels o Have tributaries and 3 layers
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o superficial lymphatics (located in subcutaneous layer deep to skin) & deep lymphatics (accompany deep arteries & veins supplying skeletal muscles & organs) these two converge to form lymphatic trunks 3) Lymphatic trunks o R/L lumbar, subclavian, jugular & bronchomediastinal trunks o Intestinal trunk 4) Lymphatic ducts o Right lymphatic duct: small; Begins: right jugular, subclavian & bronchomediastinal trunks Receives: right side of body superior to diaphragm in right subclavian. o Thoracic duct: large; Begins: inferior to diaphragm from the left side at vertebra L2 Receives lymph from: inferior parts of abdomen, pelvis, lower limbs, right & left lumbar trunks, intestinal trunk, left bronchomediastinal, left subclavian, & left jugular trunk. Cisterna Chyli: base of thoracic duct, expanded saclike chamber Lymph nodes: along collecting vessels where lymph is filtered. Cancerous cells can get trapped here & replicate.
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