The Lymphatic Systemlymphocytesessential to immune responsebind antigensmostly occur in lymphoid tissues (not in circulation)occur as B, T, and NK typesNOT phagocyticT cellsApprox. 80% of circulating lymphocytesCytotoxic T Cellsattack foreign cells or body cells infected by virusesHelper T CellsSimulate activation & function of both T cells and B cellsSuppressor T CellsInhibit activation & function of both T cells and B cellsMemory T CellsRespond to a previously encountered antigenB CellsApprox. 10-15% of circulating lymphocytesDifferentiate into plasma cells when stimulatedPlasma cells = produce & secrete antibodiesNatural Killer CellsApprox. 5-10% of circulating lymphocytesLymphatic capillaries (smallest vessels)Lack a basement membraneLarger diameter than blood capillariesHave irregular profiles/outlineEndothelial cells overlap (to act as a one-way valve)Allow free entry of virusesStart as pockets, whereas blood capillaries are continuous tubesLymphoid organs:Spleen, thymus, lymph nodesThoracic ductReceives lymph drained from entire body EXCEPT:Right arm / upper right thoracic region**this area receives lymph from right lymphatic duct insteadBOTH lymphatic and blood capillaries:Are composed of endotheliumNonspecific defenses (block/attack ANY potential infectious organism):Interferons, histamines, neutrophilsNOT immunoglobulinsNatural Killer (NK) cells (type of lymphocyte):Engage in immunological surveillanceKill cancer cellsHunt for tumor cellsComplement pathway:Group of proteins that work together, binding to antibodies and forming large holes in target cellsNatural Killer Cell sequence:1. Recognition & adhesion2. Realignment of Golgi apparatus3. Secretion of perforin4. Lysis of abnormal cellInnate Defensesphagocytes = engulf pathogens and cellular debrisinterferons = coordination of defenses against viral infectionsInflammatory response includes:Increased capillary permeabilityActivation of phagocytesClotting reaction walls off regionIncreased blood flow around injury siteProperties of the immune response:Triggered by an antigenMay be antibody-mediatedDoes not need to be acquiredMay be cell-mediatedEndogenous pyrogensReleased by activated macrophagesCause fever (hypothalamus raises body temp)Forms of Immunityimmunity that results from vaccination against influenza is classified as induced activeAutoimmune illness results from a failure of what aspect of immunity?ToleranceImmune system ignores “normal” antigens (self-antigens)The lymphocytes that enter tissues and directly attack antigens are:Cytotoxic T cellsSpecifically identify & directly kill disease cellsClass I MHCDisplays antigens found in the cytoplasm of cellsFound in membranes of all nucleated cellsWhich class of T lymphocyte is killed by the AIDS virus?Helper TSteps in antigen presentation include:Phagocytic antigen-presenting cells engulf pathogensAntigen fragments appear on the antigen-presenting cell’s surfaceAntigens are digestedClass II MHC proteinsFound only on antigen-presenting cellsPresent exogenous antigens (antigens that originated from outside the cell/phagocytized extracellular pathogens)Class I MHC proteinsRecognized by CD8 cells (destined to become a T cell)Which types of cells display protein fragments produced by the cancer within them?All nucleated cellsNucleated body cells bring pieces of endogenous proteins to the surface to display on the MHC proteinWhich major class of lymphocytes become cytotoxic T cells?CD8 cellsSteps in humoral immune defense:The antigen-specific helper T cells bind to sensitized B cellsHelper T cells secrete cytokinesThe antigen binds specifically to B cell surface**T cells DO NOT secrete immunoglobulins – these are instead derived from plasma cells which come from B cellsB CellsSensitized by exposure to antigenActivated by helper T cellsCapable of divisionWhich class of immunoglobulins sensitizes cells to allergens?IgEClasses of immunoglobulins (Ig) include:G, D, E, M, AAntigen binds to:Variable segment of each arm of an antibody moleculeThe class of antibody that produced first in the fetus at about 4 months of development is:IgMChanges in the immune system that accompany aging:Fewer helper T cellsFewer cytotoxic T cellsT cells less responsive to antigensThymic hormone production reducedImmune surveillance against tumor cells declinesBlood passes from the left ventricle to the right atrium through the following (in the order listed): 1. Elastic artery2. Muscular artery3. Arteriole4. Capillary5. Venule6. VeinArteries have endothelium that appears pleated/rippledChemical & gaseous exchange only takes place across capillary wallsthe pattern of blood flow through a capillary bed is influenced by sympathetic innervation onlycapillaries function as parts of a capillary plexusTunica Externa:Outer layer of blood vesselConnective tissue sheathContains collagen fibers w/ scattered bands of elastic fibers in arteriesThicker than tunica media & contains elastic fribers & smooth muscle cells in veinsConnective tissue fibers blend into adjacent tissues stablilization & anchoring of blood vesselTunica Media:Middle layer of blood vesselConcentric sheets of smooth muscle tissue within loose connective tissueBounded to tunica intima & externa by collagen fibersUsually the thickest layer in a small arteryExternal elastic membrane – separates tunica media from surrounding tunica externaSmooth muscle cells encircle endothelium that lines the lumen of blood vesselSmooth muscle contracts diameter of vessel decreasesSmooth muscle relaxes diameter of vessel increasesTunica Intima (Interna):Inner layer of blood vesselEndothelial lining & surrounding layer of connective tissue w/ some elastic fibersArteries outer margin contains thick layer of elastif fibers called internal elastic membraneMean arterial pressure (MAP) = diastolic pressure + pulse pressure/3(Pulse pressure = difference btwn systolic & diastolic)fenestrated capillaries are found in the choroid plexus & kidneysThe most important determinant in vascular resistance is friction between the blood and the vessel wallsAmount of friction depends on vessel length & diameterThe two major factors affecting blood flow rates: pressure & resistanceArteries vs. Veinswhen not opposed by blood pressure, arterial walls contractthe endothelial lining of an artery cannot contractarteries, when stretched, are more resilient than veinsin general, the walls of arteries are thicker than the walls of veinsThe greatest
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