Lymphatic Lymphatic SystemSystem

Chapter 12Chapter 12

IntroductionIntroduction ComponentsComponents

LymphLymph is the fluid is the fluid

Vessels – Vessels – lymphaticslymphatics

Structures & organsStructures & organs FunctionsFunctions

Return tissue fluid to the bloodstreamReturn tissue fluid to the bloodstream

Transport fats from the digestive tract to the Transport fats from the digestive tract to the bloodstreambloodstream

Surveillance & defenseSurveillance & defense

The Lymphatic SystemThe Lymphatic System

LymphaticsLymphatics Originate as lymph capillariesOriginate as lymph capillaries Capillaries unite to form larger vesselsCapillaries unite to form larger vessels

Resemble veins in structureResemble veins in structure

Connect to lymph nodes at various intervalsConnect to lymph nodes at various intervals Lymphatics ultimately deliver lymph into 2 Lymphatics ultimately deliver lymph into 2

main channelsmain channelsEmpty into large veins just before they join the Empty into large veins just before they join the superior vena cavasuperior vena cava

Lymph CapillariesLymph Capillaries

Lymphatic VesselsLymphatic Vessels

Main Channels of LymphaticsMain Channels of Lymphatics

Major Lymphatic Vessels of the Major Lymphatic Vessels of the TrunkTrunk

Lymph TissueLymph Tissue 3 types3 types

Diffuse lymphatic tissueDiffuse lymphatic tissue

Lymphatic nodulesLymphatic nodules Some are found singlySome are found singly Some are found in clusters in specific areasSome are found in clusters in specific areas

Eg. Tonsils; appendixEg. Tonsils; appendix

Lymphatic organsLymphatic organs

Lymph NodulesLymph Nodules

Lymph NodesLymph Nodes Oval structures located along lymphaticsOval structures located along lymphatics Enclosed by a fibrous capsuleEnclosed by a fibrous capsule Divided into compartmentsDivided into compartments

SinusesSinuses Produce lymphocytesProduce lymphocytes Lymph enters nodes through afferent Lymph enters nodes through afferent

lymphatics, flows through sinuses, exits lymphatics, flows through sinuses, exits through efferent lymphaticthrough efferent lymphatic

Lymph NodeLymph Node

TonsilsTonsils Multiple groups of large lymphatic nodulesMultiple groups of large lymphatic nodules Location – mucous membrane of the oral and Location – mucous membrane of the oral and

pharyngeal cavitiespharyngeal cavities Palatine tonsils Palatine tonsils

Posterior-lateral walls of the oropharynxPosterior-lateral walls of the oropharynx Pharyngeal tonsilPharyngeal tonsil

Posterior wall of nasopharynxPosterior wall of nasopharynx Lingual tonsilsLingual tonsils

Base of tongueBase of tongue

TonsilsTonsils

SpleenSpleen Largest lymphatic organLargest lymphatic organ Located between the stomach & diaphragmLocated between the stomach & diaphragm Structure is similar to a nodeStructure is similar to a node

Capsule presentCapsule presentButBut no afferent vessels or sinuses no afferent vessels or sinuses

ContainsContainsLymphatic tissueLymphatic tissueRed blood cellsRed blood cellsLymphocytes (plasma cells)Lymphocytes (plasma cells)Other leucocytesOther leucocytes

FunctionsFunctionsFilters bloodFilters bloodStores bloodStores blood

SpleenSpleen

Thymus GlandThymus Gland Location – behind the sternumLocation – behind the sternum The capsule divides it into 2 lobesThe capsule divides it into 2 lobes DevelopmentDevelopment

Infant – conspicuousInfant – conspicuous

Puberty – maximum sizePuberty – maximum size

Maturity – decreases in sizeMaturity – decreases in size FunctionFunction

Differentiation and maturation of T cellsDifferentiation and maturation of T cells

Thymus GlandThymus Gland

Function of the Lymphatic Function of the Lymphatic SystemSystem

Defense against harmful organisms Defense against harmful organisms and chemicalsand chemicals Nonspecific resistanceNonspecific resistance

InheritedInheritedWide variety of body reactions against a Wide variety of body reactions against a wide range of pathogenswide range of pathogens

Specific resistanceSpecific resistance Resistance to a specific disease-causing Resistance to a specific disease-causing

microorganismmicroorganism

Nonspecific ResistanceNonspecific Resistance SkinSkin

11stst line of defense line of defense Mechanical and chemical factors that fight diseaseMechanical and chemical factors that fight disease

TearsTears SalivaSaliva Flow of urineFlow of urine Gastric juiceGastric juice

Nonspecific Resistance Nonspecific Resistance (cont’d)(cont’d)

Interferon (IFN)Interferon (IFN)Produced by body cells infected with virusesProduced by body cells infected with viruses

Then released by the infected cellsThen released by the infected cells Inhibits viral replication in neighboring cellsInhibits viral replication in neighboring cells

Decreases disease-producing power of many Decreases disease-producing power of many virusesviruses

PhagocytosisPhagocytosis Inflammation Inflammation Fever Fever

Specific Resistance = ImmunitySpecific Resistance = Immunity

Involves the production of a specific cell or Involves the production of a specific cell or molecule (antibody) to destroy a specific molecule (antibody) to destroy a specific disease-causing organism or its toxin disease-causing organism or its toxin (antigen).(antigen).

Innate ImmunityInnate Immunity Inborn immunityInborn immunity Acquired ImmunityAcquired Immunity

Immunity acquired during organisms’ lifetimeImmunity acquired during organisms’ lifetime

Characteristics of the Immune Characteristics of the Immune ResponseResponse

Specificity Specificity Involves the production of a specific cell or antibody to Involves the production of a specific cell or antibody to

destroy a particular antigendestroy a particular antigen

MemoryMemoryAcquired ability to detect and eliminate foreign Acquired ability to detect and eliminate foreign substancessubstances Self vs. non-self recognitionSelf vs. non-self recognition

MHCMHC

Involves antibody-mediated and cell-mediated Involves antibody-mediated and cell-mediated immunityimmunity

Lymphocytes Initiate the Lymphocytes Initiate the Immune ResponseImmune Response

Types of lymphocytesTypes of lymphocytesT cellsT cells

80% of circulating lymphocytes80% of circulating lymphocytes

B cellsB cells 10 – 15% of circulating lymphocytes10 – 15% of circulating lymphocytes

NK cellsNK cells 5 – 10% of circulating lymphocytes5 – 10% of circulating lymphocytes

Derivation and Distribution of Derivation and Distribution of LymphocytesLymphocytes

Distribution and Life Span of Distribution and Life Span of LymphocytesLymphocytes

Ratio of B cells to T cells variesRatio of B cells to T cells varies Depends on the tissue or organ consideredDepends on the tissue or organ considered Lymphocytes continually move throughout the Lymphocytes continually move throughout the

body (wanderers)body (wanderers)

Lymphocytes have relatively long life Lymphocytes have relatively long life spansspans

Lymphocytes and the Immune Lymphocytes and the Immune ResponseResponse

2 components2 components Cell-mediated immunityCell-mediated immunity

Direct attack by T cellsDirect attack by T cells Virus & bacterial infected host cells, fungi, parasites, Virus & bacterial infected host cells, fungi, parasites,

transplanted tissues, tumors, etc.transplanted tissues, tumors, etc.

Antibody-mediated immunityAntibody-mediated immunityAttack by circulating antibodiesAttack by circulating antibodies

Released by plasma cells derived from activated B Released by plasma cells derived from activated B lymphocyteslymphocytes

Lymphocytes and the Lymphocytes and the Immune ResponseImmune Response

What is an antigen?What is an antigen?

Antigen = “Antigen = “antiantibody body gengenerating” molecule erating” molecule any chemical substance that, when introduced into any chemical substance that, when introduced into

the body, causes the body to produce specific the body, causes the body to produce specific antibodies that can react with the antigenantibodies that can react with the antigen

Properties of antigens:Properties of antigens: ForeignForeign proteins or polysaccharides proteins or polysaccharides

Examples:Examples: Cell membranes, flagella, viruses, toxins, enzymes, Cell membranes, flagella, viruses, toxins, enzymes,

pollen, transplanted tissues & organs, markers on red pollen, transplanted tissues & organs, markers on red blood cellsblood cells

Cell-mediated ImmunityCell-mediated Immunity

Characteristics of the Cell Characteristics of the Cell Mediated Immune SystemMediated Immune System

Upon interaction with specific antigens, specific Upon interaction with specific antigens, specific T cells produce T cells produce cytokinescytokines Proteins that activate both B & T cellsProteins that activate both B & T cells

Do not secrete antibodiesDo not secrete antibodies

Found in lymphoid tissue (nodes, blood, spleen) Found in lymphoid tissue (nodes, blood, spleen)

Act primarily on intracellular parasites (viruses, Act primarily on intracellular parasites (viruses, some bacteria), fungi & worms, cancer cells & some bacteria), fungi & worms, cancer cells & transplanted tissuestransplanted tissues

T Cells and ImmunityT Cells and Immunity 1000s of different types of T cells1000s of different types of T cells When an antigen enters the body, only the particular When an antigen enters the body, only the particular

T cell programmed to react with the antigen becomes T cell programmed to react with the antigen becomes activatedactivated

MacrophagesMacrophages phagocytize the antigen phagocytize the antigenMacrophages present it to the T cellMacrophages present it to the T cell

T cells increase in size, divide, differentiateT cells increase in size, divide, differentiateCytotoxic T cellsCytotoxic T cellsHelper T cellsHelper T cellsMemory T cellsMemory T cellsDelayed hypersensitivity T cellsDelayed hypersensitivity T cellsSuppressor T cellsSuppressor T cells

Duality of the Immune System

Cytotoxic T Cells (TCytotoxic T Cells (TCC) )

Migrate to the site of invasionMigrate to the site of invasionAttach to the invading cellAttach to the invading cell

Secrete substances that lyse the infected cell.Secrete substances that lyse the infected cell.

Secrete interferonSecrete interferon

A TA TCC Cell Lyses an Infected Cell Cell Lyses an Infected Cell

Helper T Cells (THelper T Cells (THH Cells) Cells)Assist in the regulation and coordination of he Assist in the regulation and coordination of he immune responseimmune responseSteps of regulationSteps of regulation 1. Processing1. Processing

Macrophage phagocytizes antigen, presents it on its surfaceMacrophage phagocytizes antigen, presents it on its surface 2. Recognition2. Recognition

Appropriate TAppropriate THH cell binds to the macrophage cell binds to the macrophage 3. Stimulation3. Stimulation

Macrophage stimulates TMacrophage stimulates TH H cell to form a clone of Tcell to form a clone of THH cells cells

Cloned cells produce cytokinesCloned cells produce cytokines Stimulate B cells and TStimulate B cells and TCC cells cells

4. Response4. ResponseTTCC cells kill infected cells, B cells produce antibodies cells kill infected cells, B cells produce antibodies

The Role of Helper T Cells as The Role of Helper T Cells as Mediators of Immune ResponsesMediators of Immune Responses

Memory T CellsMemory T Cells Recognize original invading Recognize original invading

organism if the pathogen invades organism if the pathogen invades laterlater

Swifter reaction than during the 1Swifter reaction than during the 1stst invasioninvasion

Pathogen is usually destroyed before Pathogen is usually destroyed before any symptoms appearany symptoms appear

Other T CellsOther T Cells Delayed hypersensitivity T cells (TDelayed hypersensitivity T cells (TDD))

Key factor in allergy responses and transplant Key factor in allergy responses and transplant tissue rejectiontissue rejection

Suppressor T cells (TSuppressor T cells (TSS))

Turn off the immune responseTurn off the immune response

Additional Cell ComponentsAdditional Cell Components

MacrophagesMacrophages Present antigen to TPresent antigen to THH cells, eliminate viral & cells, eliminate viral &

bacterial infected cells, attack cancer cells, bacterial infected cells, attack cancer cells, activated by antigen and cytokines from Tactivated by antigen and cytokines from THH cellscells

Natural Killer CellsNatural Killer Cells Attack and lyse foreign cells, normal cells Attack and lyse foreign cells, normal cells

infected with viruses, and cancer cells infected with viruses, and cancer cells Non-specific in actionNon-specific in action

Antibody-Mediated Antibody-Mediated ImmunityImmunity

B CellsB Cells 1000s of different kinds of B cells1000s of different kinds of B cells

Each type responds to a specific antigenEach type responds to a specific antigen When an antigen enters the bloodWhen an antigen enters the blood

B cells are activatedB cells are activated Become plasma cellsBecome plasma cells Circulate in blood and lymph to reach site of Circulate in blood and lymph to reach site of

invasioninvasion

B cells become memory B cellsB cells become memory B cells Respond more rapidly and forcefully should a Respond more rapidly and forcefully should a

22ndnd invasion occur invasion occur

What does an antigen do?What does an antigen do?

Antigen with its antigenic determinant stimulates Antigen with its antigenic determinant stimulates the formation of specific antibodies the formation of specific antibodies

The antigenic determinant, a portion of the The antigenic determinant, a portion of the antigen, reacts with an antibody to form an antigen, reacts with an antibody to form an antigen-antibody complexantigen-antibody complex

The formation of the antigen-antibody complex The formation of the antigen-antibody complex ultimately leads to inactivation and removal of ultimately leads to inactivation and removal of the antigenthe antigen

Antigenic Determinants on an Antigenic Determinants on an AntigenAntigen

What is an antibody?What is an antibody?

Large ProteinsLarge Proteins

Basic subunit has minimum of two binding sites Basic subunit has minimum of two binding sites at which it combines with antigensat which it combines with antigens Also known as “immunoglobulins”Also known as “immunoglobulins”

Antibody ConfigurationAntibody Configuration

2 Methods of Antibody 2 Methods of Antibody ProductionProduction

T cell independent productionT cell independent production B cells differentiate without the interaction of B cells differentiate without the interaction of

TTHH cells cells

T cell dependent productionT cell dependent production B cells differentiate with the interaction of TB cells differentiate with the interaction of THH

cellscells

T cell Independent AntigensT cell Independent Antigens

T cell Dependent Antigens & T cell Dependent Antigens & Antibody ProductionAntibody Production

Outcome of Antibody Outcome of Antibody Production by B cellsProduction by B cells

Disorders of the Immune Disorders of the Immune SystemSystem

AllergyAllergyPerson is overly reactive to an antigenPerson is overly reactive to an antigen

Autoimmune diseasesAutoimmune diseasesBody has difficulty in discriminating between its own antigens Body has difficulty in discriminating between its own antigens and foreign antigensand foreign antigens

Severe Combined Immunodeficiency (SCID) Severe Combined Immunodeficiency (SCID) Both T cells and B cells are absent or inactiveBoth T cells and B cells are absent or inactive

Acquired Immune Deficiency Syndrome (AIDS)Acquired Immune Deficiency Syndrome (AIDS) Human immunodeficiency virus (HIV)Human immunodeficiency virus (HIV)

Primarily attacks helper T cellsPrimarily attacks helper T cells