Lymphatic System

Lymphatic SystemImmune SystemOverview of the Lymphatic System:cells, tissues, and organs responsible for defending the body against both environmental hazards (pathogens) and internal threats (cancer)Pathogens: viruses, bacteria, fungi, and parasites capable of not only surviving but thriving inside our bodiesImmune response: cells of the immune system that provide a specific response as a defense against pathogenImmunity: Ability to resist infection and disease through the activation of specific defenses.

Organization of the Lymphatic SystemLymph: plasma-like fluid

Lymphatic vessels: begin intissues and end in connectionsto veins

Lymphoid tissues and organs

Lymphocytes and other cells

Interesting facts

The body has between 501 and 700 lymph nodes (the number of nodes varies from individual to individual).About half of the nodes are in the middle of your body (stomach or abdominal cavity).The lymph nodes near your armpits and groin have about 100 nodes.

Functions of the Lymphatic System

Produce, maintain and distribute lymphocytesProduced inside the lymphoid tissues and organsTonsils, spleen, thymus, red bone marrow, appendix

Provide defense against infections and environmental hazardsMust be able to detect problemsMust be able to reach the infection or injury siteCirculate in the blood

Lymphatic Vessels

Lymphatic vessels carry lymph from the tissues to the venous (veins) system.Vessels have valves to allow entrance into the vessels for fluids, proteins, viruses and bacteria but prevents them from flowing back into the intracellular spacesLymphatic capillaries are the smallest of these vesselsPresent in almost every tissue and organ in the body

Lymphatic Vessels

Occur in association with blood vessels but are smaller and more numerousMajor lymph collecting vesselsSuperficial lymphatics: located in the deep subcutaneous layer of the skin and in the lining of the digestive, respiratory, urinary, and reproductive tractsDeep lymphatics: larger, accompany deep arteries and veins in the limbs and trunkDeep and superficial come together to form larger vessels called trunksThese empty into two large collecting vessels

Lymphatic Vessels

Thoracic ductbegins below the diaphragmcollects lymph from the left side of the head, neck, thorax and inferior portion of the bodyempties it into the left subclavian vein to reenter into venous circulationRight lymphatic ductformed from the merging of major blood vessel trunks on the right side of the bodyempties into the right subclavian vein.

LymphodemaBlockage of lymphatic drainage from the limbs Fluid accumulates in the limb and gradually becomes swollenCan be permanent if the condition persistsDangerous if an infection develops in that areaWhy?

Lymphocytes Lymph cells3 classesEach has its own biochemical and functional characteristicsT cells (thymus-dependant)B cells (bone marrow-derived)NK cells (natural killer)pit bulls of the lymphatic system

T cells: 80% of lymphocytes

Cytotoxic T cells

Helper T cells

Suppressor T cells

Inflammatory T cellsAttack foreign cells or body cells infected with a virus

Stimulate the activation and function of both T cells and B cells

Inhibit the activation and function of both T cells and B cells

Stimulate regional inflammation and local defenses in injured tissueOther lymphocytesB cellsNK cells10-15 % of lymphocytesCan differentiate into plasma cellsResponsible for producing antibodiesThese bind to specific chemical targets called antigensAntigens are typically pathogens, parts of pathogensSome lipids, polysaccharides and nucleic acids can stimulate antigen body production

5-10 % of lymphocytesAlso known as large granular lymphocytesAttack foreign cells, normal cells infected with viruses, and cancer cells (often Dr.s measure #s of these to measure if cancer cells are growing or declining)Continuous policing is called immunological surveillance

Life span and circulation of lymphocytesThey are not evenly distributed throughout the bloodT cells move around the body quicklyB cells are much slowerMajority of lymphocytes have long life spans (4 years +)Some may live up to 20 yearsYou maintain your lymphocyte populations by making new lymphocytes in bone marrow and lymphiod tissue

Lymphocyte Production

Lymphopoiesis (lymphocyte production) involves bone marrow, thymus, and peripheral lymphoid tissues.Lymphocytes originate from stem cells

Division of stem cells in the bone marrow that produce immature B and NK cells, as they mature they begin to circulate in the blood stream.Second division of stem cells migrates to the thymusIn the thymus these cells produce various kinds of T cells, when they mature they enter the blood stream.

Lymphoid Tissues:Connective tissue dominated by lymphocytes

Lymphoid nodule: lymphocytes are densely packedLarge clusters of nodules existTonsils: most people have 5When the pair in the base of the pharynx become infected we get tonsillitisGerminal center: central zone of the nodule where lymphocytes divide

Lymphoid Tissues: dominated by lymphocytes

MALT: Mucosa-Associated Lymphoid TissueCollection of lymphoid tissue linked with the digestive tractPeyers patches are cluster of nodules in the lining of intestines

Lymphoid Organs

Lymph nodes: small lymphoid organ surrounded by connective tissueBean shapedHilus is the indentation of the bean where nerve and blood flow reach the nodeLymph flow: through open passageways with incomplete walls called sinus Then through the outer cortex of the nodeThen continues to the deep cortex and into the core or medulla of the lymph node

Lymph Node Function

Purifies lymph before it reaches the vesselsLike a water filterEarly warning system for the bodyPathogens stimulate macrophage/lymphocyte production in nodesLymph glands at the groin, axilla (armpit), and base of the neck act as guards to protect the trunk for pathogensMinor injury/infection causes swollen glands when lymph nodes respond to injury/infection by increasing production of phagocytes and lymphocytes

Thymus

Pink, grainy organ located behind the sternumProduce T cellsSurrounding blood vessels allow T cells to enter the blood streamReview:Thymus also produces hormones (endocrine system)Thymosin is a hormone that promotes development of lymphocytes

Spleen

Largest collection lymphoid tissueProvides same services for the blood that lymph nodes do for the lymph Remove abnormal blood cells/components by phagocytosis (think of pac-man)Storage of iron recycled from red blood cellsInitiation of immune response by B cells and T cells in response to antigens in the blood

Spleen

Blood circulates through and allows phagocytes in the spleen to engulf damaged or infected cells in the bloodInfection (such as mono) can cause the spleen to become enlargedThe spleen is fragileWhen it is enlarged any blow to the left side of the body can cause it to rupture

Non-specific defenses: prevent the approach, deny entry, or limit the spread of microorganisms or other environmental hazards.Categories1. Physical barriers2. Phagocytes3. Immunological surveillance4. Interferons5. Complement6. Inflammatory response7. Fever

Physical BarriersKeep hazards outside the body (example: hair on your head helps keep mosquitoes off)In order for a pathogen to cause trouble it has to enter the body.Cross the epithelium (skin) through a mucus membrane (mouth, nose, eyes, etc)Accessory structures help with the barrier (eyelashes, hair, glands that secrete oil or chemicals/enzymes)

Phagocytes: engulf pathogens and debris

Microphages (small)Circulate in the blood, leave to travel into tissues to engulf and destroy pathogens/antigensMacrophages (big)Several types, in almost every tissue of the bodyWork byEngulfing particle and destroying it with and enzymeBing or remove particle from fluid and receive help from other cells to destroy itReleasing toxic chemicals to destroy particleFixed macrophages: permanent residents of a tissueFree macrophages: mobile and travel through the body to arrive at injury sites

Phagocytes:

Movement and phagocytosis

Free and fixed macrophages characteristicsBoth can move through capillary wallsBoth may be attracted or repelled by chemicals ins the surrounding fluid (chemotaxis)Both use adhesion (attachment of the phagocyte to its target) and then formation of a vesicle (capsule) that is digested with help of an enzyme

Immunological surveillance: destruction of abnormal cells by NK cells

The immune system usually ignores your bodys own cells unless they have become abnormal in some way (such as mutated cells or cells infected with a virus)mutations-can lead to what?Immunological surveillance:NK cells monitor tissues looking for and destroying abnormal cells in any tissue of the bodyNK cells are highly versatileRespond very rapidly

Immunological surveillance:

Cancer cells membranes contain proteins called tumor-specific antigensNK cells recognize them as abnormal and destroy themHowever, some cancer cells go undetected through immunological escape:Escape destruction by: avoiding detection, covering their antigens somehow, or killing NK cellsOnce escaping detection, cells can multiply and spread

Interferons: chemical messengers that coordinate defenses against virusesInterferons are small proteins released by lymphocytes, macrophages, and tissues infected with a virusTrigger the production of antiviral proteins which interfere with viral replication inside the cellsStimulate the activities of macrophages and NK cells

Complement: chemical messengers that coordinate defenses against viruses11 special complement proteins: complement the actions of antibodiesComplement Activation: Classical Pathway (rapid and effective)One complement protein binds to an antibody molecule already attached to its antigenIt then acts as an enzyme starting a series of reactions with other complement proteinsComplement: Alternative Pathway (slower and less effective)Occurs when there is no antibody moleculeSeveral complement proteins interact in the plasma to defend against bacteria, parasites, and virus infected cellsComplement: chemical messengers that coordinate defenses against virusesEffects of Complement ActivationStimulation of InflammationEnhance the release of histamine to accelerate inflammationAttraction of Phagocytes: to increase destruction of pathogensEnhancement of Phagocytosis: complement proteins make target cells easier to engulfDestruction of Target Cell Membranes: so they are easier to destroyInflammatory response: local response to injury of infection at the tissue level (limits spread of injury, combats infection)5 Signs of inflammation: SwellingRednessHeatPainLoss of functionEffectsInjury is temporarily repaired and pathogens are kept outSpread of pathogens away for the injury is slowedDefenses are mobilized to overcome pathogens and allow for permanent repairs

Inflammatory response:

Tissue response to injury (in a nut shell)Mast cells release histamine in to the blood stream to start the inflammatory responseIncreases cell permeability and increases blood flow by vasodilation (widening of the vessels)Clot forms around the injured areaComplement activation breaks down bacterial cell walls and attracts phagocytesSpecial defenses are activatedMacrophages engulf debris (dead cells, dirt etc) and pathogensFibroblast are stimulated to repair damaged tissueOver time the clot is broken down and the tissue is repaired to normalTissue death (necrosis) or infection occurs if the immunological response fails Pus is accumulation fluid with dead cells and necrotic tissueAbscess is accumulation of pus in an enclosed areaInflammation (itis)

Fever: elevation of body temperature that accelerates tissue metabolism and defensesMaintenance of a body temperature of greater than 99 degrees FA response to a variety of stimuli including pathogensWithin limits it can be beneficialInhibits some viruses and bacteriaIncreases cell metabolism (for each degree increase metabolic rate increases by 10%)Cells move faster, reactions are quickerLeads to faster defenses and repair

An Antigen

An antigen is any substance that causes your immune system to produce antibodies against it. Substance may be from the environment or formed within the body. The immune system will kill or neutralize any antigen that is recognized as a foreign and potentially harmful invader. The term originally came from antibody generator and was a molecule that binds specifically to an antibody

Specific DefensesCell mediated immunity: defends against abnormal cells and pathogens in the bodyResponsibility of T cellsT cells cannot respond to antigens in solutionAntibody mediated immunity: defends against antigens and pathogens in body fluidsResponsibility of B cellsCannot cross cell membranes

Forms of Immunity

Innate: genetically determinedPresent at birthNo relationship to exposure to antigenAcquired: not present at birthafter being exposed to a specific antigenActive: develops after exposure to an antigen as a consequence of the immune responseNaturally acquired active immunity: begins after birth, constantly changes as you are exposed to new antigens Induced active immunity: stimulation of antibodies under controlled situations: vaccinationForms of Immunity

Passive immunity: produced by the transfer of antibodies from another sourceNaturally acquired: when a child is protected by a mothers antibodies in utero and in breast milkInduced: antibodies are administer to fight infection or prevent disease (like when you receive antibodies after exposure to bacteria)

Properties of Immunity

Specificity: defense activated by a specific antigen-targets that antigen and nothing else.Shape/size of the antigen determines what lymphocyte responds.Versatility: your immune system encounters tens of thousands of antigens in you lifetime, there is no way to know which it will encounter. The diversity of lymphocytes allows the body to be versatile in its defenses. When a specific lymphocyte is activated by and antigen it begins to divide and make clones.Properties of Immunity

Memory: exists because when lymphocytes divide one group is allowed to destroy the antigen, and one group remains inactivated so it can be used if you come into contact with the same antigen again.

Tolerance: happens when an antigen does not stimulate an immune response, such as in a constant exposure to an antigenThe Creepy Virus

A virus particle attaches to a host cell.The particle releases its genetic instructions into the host cell.The injected genetic material recruits the host cell's enzymes.The enzymes make parts for more new virus particles.The new particles assemble the parts into new viruses.The new particles break free from the host cell. (which usually dies)Each virus inside it goes on to find new hosts--repeat

Primary Responses to Antigen Exposure

Primary response: initial response to an antigenBecause the presence of an antigen activates B cells that then have to differentiate into plasma, the primary response takes time to developAs plasma cells differentiate the concentration slowly rises and does not peak until about 2 weeks after exposure to the antigenOften this is slow response allows the initial exposure to the antigen to cause an infection

Secondary Responses to Antigen Exposure

Secondary response: extensive and prolonged immune response when an antigen is introduced more than once.Response is heightened because there is an increased number of memory cells ready to destroy the antigenB cells do not have to take time to differentiate into plasma because that has already been done with the first exposure, so response is much quickerThis response often prevents exposure of the antigen a second time from causing an infection

Immune Disorders: because of the complexity of the immune response, there is opportunity for things to go wrong

Autoimmune disorders

The immune system normally ignores (self-antigens) antigens found in the body normallyAutoantibodies are B cells that activate against self antigensRheumatoid arthritis occurs when autoantibodies attack connective tissue in the jointsDiabetes can be caused by autoantibodies attaching cells in the pancreas that control insulin

Immune Disorders Cont:

Immunodeficiency disease

Result from:Problems in the development of the lymphoid organs/tissuesViral infections such as HIV that suppresses immune functionTreatment of exposure to immunosuppressive agentsSevere combined immunodeficiency disease (SCID): persons born SCID fail to produce cell or antibody mediated immunity.even mild infections can be fatalOften have to be isolated (bubble boy)Immunosuppressive drugs: used to prevent patients from rejecting transplantsCan destroy stem cells and lymphocytes and lead to complete immunological failureAllergies

Inappropriate or excessive immune responses to antigensCan damage other cells in the process of destroying antigensCan trigger massive inflammation-Mast cells release histamine that starts the inflammatory processAllergens: antigens that trigger allergic reactionsAntihistamine: drug that blocks the action of histamine

Rapid and especially severe response to an antigenFirst response is typically mild or unnoticeableSecond response: histamine and heparin from mast cells are released to produce massive inflammationT cells and macrophages are drawn to the area and further the responseIt may be isolated in a tissue, if it enters the blood stream it can be lethal

Anaphylactic Shock

Immediate Hypersensitivity

Anaphylaxis: circulating antigens affect mast cell throughout the bodyMassive swellingContraction of muscles along the respiratory tract Vasodilatation can lead to collapse or anaphylactic shockAntihistamines can prevent some of these symptoms if administered quickly

Integration with other systems

Gets help from:

Helps out:

CNS innervates the lymph system and spleenCirculatory system helps distribute lymphocytesSkeletal system produces lymphocytes in red marrowEndocrine system hormones help stimulate lymphocyte productionIntegumentary system is a physical barrier and home to mast cellsEvery system by surveying all tissues and destroying any potentially harmful invadersHelps with fluid circulation throughout the body