BSC 2086 1st Edition Lecture 14 Outline of Last Lecture I. Pressure and ReabsorptionII. Cardiovascular RegulationIII. Cardiovascular Response to Exercise and HemorrhagingIV. Other Cardiovascular AdaptationsV. Pulmonary and Systemic PatternsVI. Effects of Aging Outline of Current Lecture I. Introduction to Lymphatic SystemII. Major Structures III. LymphocytesIV. Lymphoid System Components V. Lymphatic System and Body Defenses Current LectureI. Introduction to Lymphatic Systema. Pathogens: microscopic organisms that are able to cause disease, each attacking in a specific wayi. Include viruses, bacteria, fungi and parasitesb. Immunity: ability to resist infection and diseasei. All types of cells and body tissues are involved in immunity, it is not exclusive to the lymphatic systemii. Defenses:1. Nonspecific defenses example is our skin/epidermis which protects our organs and muscles a. Block/attack any potentially infectious organismb. Cant distinguish between attacks, works on everything non-selectively2. Specific defenses a. Include lymphocytes which are part of the immune systemb. Will identify, attack and develop immunity to a certain pathogenc. The lymphatic system protects us against diseased. Cells of the lymphatic system respond to environmental pathogens, toxins and abnormal body cells (ex. Cancers)II. Major Structures a. Organizationi. Lymph plasma-like fluid without the plasma proteinsii. Lymphatic vessels carry lymph to the venous system form the peripheral tissues iii. Lymphoid tissues and lymphoid organsiv. Immune system cells including lymphocytes and phagocytesb. Functions of Systemi. Produce, maintain and distribute lymphocytes 1. Lymphocytes will detect problems and travel into injury or infection sites c. Production of lymphocytesi. Produced in:1. Lymphoid tissues a. Example: Tonsils2. Lymphoid organs a. Example: spleen, thymus3. Red bone marrow d. Circulation i. Lymphocytes 1. Blood interstitial fluid (IF) capillaries2. Returns to venous blood through lymphatic vesselsii. Fluids 1. Blood plasma lymph back to venous system2. Transports hormones, wastes and nutrients iii. Lymphatic vessels carry lymph1. Lymphatic system begins with lymphatic capillaries (smallest vessels)2. Differ from blood capillaries in that they:a. Start as pockets rather than tubesb. Have larger diametersc. Have thinner wallsd. Flat or irregular outline in sectional view iv. Lymphatic capillaries 1. Consist of endothelial cells loosely bound together with overlap2. Overlap acts as a one way valve a. Allows fluids, viruses, bacteria and solutes to enter but prevents return to intercellular spaceb. Edema of tissues causes the overlap to separate, which permits fluid into the lymphatic capillaries v. Lymph flow1. From lymphatic capillaries to the larger lymphatic vessels which have one way valvesa. Lymphatic vessels travel with veins2. Transport lymph to the (right) lymphatic duct and (left) thoracic duct a. Thoracic duct is connected to subclavian vein, therefore it combines with venous return 3. Right lymphatic duct drains upper right thoracic region, head and arm4. Left thoracic duct drains rest of body vi. Lacteals: special lymphatic capillaries1. Found in small intestine2. Transport lipids absorbed from the digestive tract vii. Lymphedema 1. Severe swelling due to the blockage of lymph drainage from a limb2. Interferes with the function of the immune systema. Toxins and pathogens unable to drain will build up in swollen area and can overwhelm local defenses without triggering immune system responseb. Connective tissues can lose elasticity and the swelling will become permanent if the problem is persistent III. Lymphocytesa. Make up about 20-30% of circulating leukocytesi. Most stored, not circulatingb. Types:i. T cells1. Thymus dependent 2. Make up 80% of circulating lymphocytes3. Main types include:a. Cytotoxic T (TC) cells i. Make cell-mediated immunity ii. Attack cells that have been infected by virusesb. Memory T cellsi. Remain in bodyii. “Remember” immunityiii. Made in response to foreign substance exposure c. Helper T (TH) cellsi. Stimulate function of T and B cells d. Suppressor T (TS) cells i. Inhibit function of T and B cells ii. B cells1. Responsible for humoral (blood) immunity2. 10-15% if circulating lymphocytes3. Change (differentiate) into plasma cells which make and secrete antibodies (immunoglobulin proteins)a. Antigens – identify any pathogen or foreign compoundb. Antibodies (immunoglobulins) – the binding of a specific antibody with its specific target antigen starts antibody-mediated immunityi. This is the chain of events that destroy target compound or organism iii. NK cells 1. Aka. Large granular lymphocytes2. 5-10% of circulating lymphocytes3. Responsible for immunological surveillance a. Attack foreign cells, virus-infected cells and cancer cellsc. Distributioni. Different T and B cell populations found in tissues1. B cells rarely found in thymus2. T cells outnumber B cells in bloodii. Wander through tissues, enter the blood vessels or lymphatics for transport iii. Can survive for many years, 80% living up to 4 years and others lasting more than 20 years d. Productioni. Lymphopoiesis involves:1. Bone marrow2. Thymus 3. Peripheral lymphoid tissuesii. Hemocytoblasts found in bone marrow, divide into 2 types of lymphoid stem cellse. Stem Cellsi. Group 11. Develops with the help of stromal cells and remains in bone marrow a. Produce the cytokine interleukin-7 to promote B cell differentiation2. Produce B cells and NK cells ii. Group 21. Migrates to thymus 2. Make T cells in environment isolated by blood-thymus barrier f. T and B cells i. Migrate through the body and defend peripheral tissuesii. Retain their ability to divide:1. Make daughter cells of the same type2. Ability is essential to immune system functionIV. Lymphoid System Components a. Lymphoid tissues connective tissues dominated by lymphocytesi. Mucosa-Associated Lymphoid Tissue (MALT)1. Protects the epithelia of the digestive, reproductive, urinary, and respiratory organ systems2. Includes lymphoid tissues associated with digestive system3. Aggregated lymphoid nodulesa. Peyer’s patchesb. Clustered deep inside intestinal epithelial lining 4. Appendixa. Vermiform Appendixb. Contains mass of fused lymphoid nodules b. Lymphoid nodules areolar tissues filled with lymphocytesi. Germinal center has dividing lymphocytes 1. Located in central zone of the noduleii.
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