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Chapter 20

lymphatic System

and Immunity

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IntroductionIntroduction Network of vessels - Transport body Network of vessels - Transport body

fluidsfluids Lymphatic vesselsLymphatic vessels

Collect excess fluidCollect excess fluid Carry excess fluid from spaces Carry excess fluid from spaces

between cellsbetween cells Special vessels called lacteals – Special vessels called lacteals –

transport fats to circulatory systemtransport fats to circulatory system Organs of lymphatic system – defend Organs of lymphatic system – defend

against disease.against disease.

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Lymphatic systemLymphatic system

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Lymphatic pathwaysLymphatic pathways Start as lymphatic capillaries – merge Start as lymphatic capillaries – merge

to form larger vessels.to form larger vessels. Empty into circulatory system.Empty into circulatory system. Tiny closed ended tubes that extend into Tiny closed ended tubes that extend into

interstitial spacesinterstitial spaces Receive tissue fluid through thin wallsReceive tissue fluid through thin walls

Once fluid is inside, called Lymph.Once fluid is inside, called Lymph. Vessels – thinner than veins, but have 3 Vessels – thinner than veins, but have 3

layers and valveslayers and valves Larger vessels pass through lymph nodes Larger vessels pass through lymph nodes

and merge to form trunks.and merge to form trunks. Trunks and ductsTrunks and ducts

Drain lymph from bodyDrain lymph from body Named for regions they drainNamed for regions they drain Join thoracic duct or right lymphatic Join thoracic duct or right lymphatic

duct.duct. Dump into subclavian veinsDump into subclavian veins

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Tissue fluid and Tissue fluid and Formation of LymphFormation of Lymph

Tissue fluid becomes lymph when Tissue fluid becomes lymph when it enters lymphatic capillaryit enters lymphatic capillary

Lymph formation depends on Lymph formation depends on tissue fluid formationtissue fluid formation

Tissue fluid formationTissue fluid formation Tissue fluid – water + dissolved Tissue fluid – water + dissolved

substancessubstances During filtration, some fluid is forced During filtration, some fluid is forced

into lymphatic capillariesinto lymphatic capillaries

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Lymph MovementLymph Movement

Skeletal muscle contraction, Skeletal muscle contraction, breathingt etc force lymph breathingt etc force lymph through vesselsthrough vessels

Edema – condition that Edema – condition that interferes with lymph flowinterferes with lymph flow Surgery may result in removal of Surgery may result in removal of

lymphatic vesselslymphatic vessels

Lymph nodesLymph nodes Contains lymphocytes and Contains lymphocytes and

macrophagesmacrophages Located along lymphatic Located along lymphatic

pathwayspathways Structure – bean shapedStructure – bean shaped

Hilum – indented area where Hilum – indented area where blood vessels enterblood vessels enter

Connecive tissue coveringConnecive tissue covering Occur in chains along lymph Occur in chains along lymph

vesselsvessels Function – filter lymph, Function – filter lymph,

remove bacteria and cellular remove bacteria and cellular debrisdebris

Centers of lymphocyte Centers of lymphocyte productionproduction

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Lymph Node LocationsLymph Node Locations

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Lymph nodeLymph node

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ThymusThymus Soft, bi-lobed organ behind Soft, bi-lobed organ behind

sternumsternum Shrinks during lifetimeShrinks during lifetime Surrounded by Connective Surrounded by Connective

tissue capsuletissue capsule Lobules contain lymphocytesLobules contain lymphocytes

Some mature into T Some mature into T lymphocytes which provide lymphocytes which provide immunityimmunity

Secretes thymosin-hormone Secretes thymosin-hormone that influences t lymphocyte that influences t lymphocyte maturationmaturation

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SpleenSpleen Located in upper left Located in upper left

abdominal cavityabdominal cavity Largest lymphatic organLargest lymphatic organ Looks like lymph node, Looks like lymph node,

but contains bloodbut contains blood Contains white and red Contains white and red

pulppulp Filters blood and removes Filters blood and removes

damaged blood cells and damaged blood cells and bacteriabacteria

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Flu attackFlu attack

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Body Defenses against Body Defenses against InfectionInfection

Pathogens – disease causing Pathogens – disease causing agents – produce infectionsagents – produce infections

2 Lines of defense2 Lines of defense Non specific – guards against Non specific – guards against

any pathogenany pathogen Specific (immunity) – mounts Specific (immunity) – mounts

response against very specific response against very specific targettargetCarried out by lymphocytes that Carried out by lymphocytes that

recognize invaderrecognize invader

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Non SpecificNon Specific Species Resistance – resistant to diseases that affect Species Resistance – resistant to diseases that affect

other species – unique chemical other species – unique chemical environment/temperatureenvironment/temperature

Mechanical barriers – unbroken skin/mucous Mechanical barriers – unbroken skin/mucous membranes prevent entrymembranes prevent entry First line of defenseFirst line of defense

Chemical barriers – high acidity or caustic Chemical barriers – high acidity or caustic environment provided by gastric juice, or lysozyme environment provided by gastric juice, or lysozyme in tears.in tears. Interferons – antiviral – produced by infected cells to Interferons – antiviral – produced by infected cells to

protect othersprotect others Fever – interferes with favorable conditions that Fever – interferes with favorable conditions that

promote bacterial growthpromote bacterial growth Iron is reduced, fewer nutrientsIron is reduced, fewer nutrients Phagocytic cells increase vigor of attackPhagocytic cells increase vigor of attack

Inflammation – redness, swelling, heat, painInflammation – redness, swelling, heat, pain Increase of blood volume, dilation of blood vessels, Increase of blood volume, dilation of blood vessels,

invasion of white blood cells, fibroblast sac productioninvasion of white blood cells, fibroblast sac production Phagocytosis by macrophage remove invadersPhagocytosis by macrophage remove invaders

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MacrophageMacrophage

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Specific (immunity) Specific (immunity)

22ndnd line of defense line of defense Attack against specific Attack against specific

recognized foreign moleculerecognized foreign molecule AntigensAntigens

Self inventory taken before Self inventory taken before birthbirth

Antigens - non self - produce Antigens - non self - produce immune responseimmune response

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AntigensAntigens Self inventory before birthSelf inventory before birth Body responds to non-self substancesBody responds to non-self substances Antigens elicit immune responseAntigens elicit immune response

Lymphocyte originsLymphocyte origins

Fetal development – red bone Fetal development – red bone marrow releases lymphocytesmarrow releases lymphocytes Most become t cells, remainder become Most become t cells, remainder become

b cellsb cells B and t cells stay in lymphatic organs.B and t cells stay in lymphatic organs.

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Lymphocyte FunctionsLymphocyte Functions

T cellsT cells Cell-mediated immunity - Attack foreign cells Cell-mediated immunity - Attack foreign cells

such as bacteriasuch as bacteria Attack foreign particles by cell to cell contactAttack foreign particles by cell to cell contact

Secrete cytokinesSecrete cytokines Enhance cellular response to antigensEnhance cellular response to antigens

Secrete toxins that kill target cells or inhibit Secrete toxins that kill target cells or inhibit growthgrowth

B cellsB cells Become plasma cells which produce antibodies Become plasma cells which produce antibodies

- antibody mediated immunity- antibody mediated immunity

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T cells and cellular T cells and cellular immune responseimmune response

Requires presence of antigen-presenting Requires presence of antigen-presenting cell that has already encountered antigen.cell that has already encountered antigen.

Encounters macrophage displaying Encounters macrophage displaying antigen. If antigen fits helper t cells antigen. If antigen fits helper t cells antigen receptor, it is activatedantigen receptor, it is activated

Cytotoxic t cells - eliminate tumor and Cytotoxic t cells - eliminate tumor and virus infected cells by releasing perforinvirus infected cells by releasing perforin

Memory t cells - future response to Memory t cells - future response to antigenantigen

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Killer cellsKiller cells

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B cells and Humoral B cells and Humoral Immune responseImmune response

B cell activatedB cell activated Produces cloneProduces clone Normally requires presence of helper Normally requires presence of helper

t cellst cells T cell releases cytokines that activate T cell releases cytokines that activate

it so it can form a cloneit so it can form a clone Plasma cells produce and secrete Plasma cells produce and secrete

antibodiesantibodies

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Macrophages, b-cellsMacrophages, b-cells

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Types of antibodiesTypes of antibodies Antibodies - immunoglobulinAntibodies - immunoglobulin

IgGIgG Defends again bacteria, viruses and toxinsDefends again bacteria, viruses and toxins

IgA IgA in exocrine gland secretionsin exocrine gland secretions

IgMIgM In plasma - activates complement In plasma - activates complement Reacts with blood cells in transfusionsReacts with blood cells in transfusions

IgDIgD B cell activationB cell activation

IgEIgE Promotes allergic reactionsPromotes allergic reactions

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Classification of Classification of immunityimmunity

Natural active - occurs after Natural active - occurs after exposure to pathogenexposure to pathogen

Artificially acquired active – through Artificially acquired active – through vaccinesvaccines

Artificially acquired passive – Artificially acquired passive – injection of antibioticsinjection of antibiotics

Naturally acquired passive – Naturally acquired passive – antibodies passed to fetusantibodies passed to fetus

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Allergic reactionsAllergic reactions

Excessive immune responses - may Excessive immune responses - may lead to tissue damagelead to tissue damage

Delayed reaction - repeated exposureDelayed reaction - repeated exposure Immediate reaction - inheritedImmediate reaction - inherited Histamine Anaphylactic shockHistamine Anaphylactic shock

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Transplantation and Transplantation and tissue rejectiontissue rejection

Immune system reacts with foreign Immune system reacts with foreign antigensantigens

Tissue rejectionTissue rejection Donor match reduce change of Donor match reduce change of

rejectionrejection

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AutoimmunityAutoimmunity

Antibodies produced against own Antibodies produced against own antigensantigens

Autoimmune disorders – may result Autoimmune disorders – may result from virus, t cell development, from virus, t cell development, reaction to nonself antigen that bears reaction to nonself antigen that bears close resemblance to self antigen.close resemblance to self antigen.