Lymphatic System and Body Defenses

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Lymphatic System and Body Defenses

• Chapter 12

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Lymphatic System

• 2 parts
• Lymphatic vessels
• Transport back to blood, fluid escaped from CV
• Lymphoid tissues and organs
• House phagocytes and lymphocytes

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Lymphatic Vessels

• As blood circulates, hydrostatic and osmotic
  pressure force fluid out of arterial ends at
  capillary bed and in at venous ends
• Fluid that remains up to 3L a day leaked plasma
  proteins must be returned to blood for vascular
  system to function
• Edema impairs cells ability to exchange
• Drainage system picks up lymph and returns to
  blood

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Lymphatics

• One way system -gt heart
• Blind ended lymph capillaries between tissue
  cells and blood capillaries in loose connective
  tissue, absorbed leaked fluid

Figure 12.2
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Lymphatic Capillaries

• Very permeable
• Endothelial cells loosely overlap forming
  minivalves
• Collagen fibers anchor to CT
• Open when interstitial fluid pressure greater,
  fluid enters lymphatics
• Close when pressure in lymphatic capillary,
  forces lymph along capillary
• Anything can enter!!
• Whats the problem?
• Detours!

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Lymph Transportation
Figure 12.1

• From lymph capillaries to lymphatic collecting
  ducts to venous system by right lymphatic duct or
  thoracic duct
• Thin walled, larger have valves
• Low pressure, pumpless system, transportation
  same as veins smooth muscle in larger
  lymphatics contract rhythmically to move

Figure 12.3
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Lymph Nodes What are they?

• Protection remove foreign material, produce
  lymphocytes (immunity)
• Lymph travels toward heart filtered by 1000s of
  nodes
• Large clusters found in axillary, inguinal,
  cervical regions
• Macrophages and lymphocytes
• Swollen glands

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Lymph Nodes - Structure

• Most kidney shaped
• Fibrous capsule, trabeculae extend inward
  dividing
• Internal structure of reticular CT
• Outer Cortex, follicles with dark staining
  center called germinal centers
• Inner Medulla, macrophages

Figure 12.4
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Follicles of the lymph node

• Follicles contain collections of lymphocytes
• Germinal centers enlarge when B cells
  (lymphocyte) generating daughter cells plasma
  cells
• T cells are other lymphocyte

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Travel Through Lymph Node

• Lymph enters convex side through afferent vessels
• Sinuses
• Exits hilum via efferent vessels
• of efferent lt of afferent, drainage slow,
  time for macrophages and lymphocytes to work
• Can get clogged tender or not?

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Other Lymph Organs - Spleen

• Blood rich, filters blood of bacteria, viruses
  and debris
• Site for lymphocyte proliferation and
  surveillance
• Destroys worn-out RBC, returns break down to
  liver iron
• Stores platelets and blood reservoir (liver)
  hemorrhaging
• Fetus hematopoietic site, Adults only
  lymphocytes produced

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Other Lymph Organs - Thymus Gland

• Over heart
• Peak function in youth
• Hormone Thymosin -gt programming of T cell
  lymphocytes

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Other Lymph Organs - Tonsils

• Ring pharynx
• Trap and remove bacteria and foreign pathogens
  entering throat
• Can become congested with bacteria, red, swollen,
  sore
• Part of MALT

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Other Lymph Organs Peyers Patches

• Wall of small intestine
• Macrophages
• Capture and destroy bacteria before able to
  penetrate intestinal wall
• Part of MALT mucosa-associated lymphatic tissue
• Protect upper resp. and digest. from foreign
  matter always entering

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Body Defenses
Figure 12.6

• Two systems Innate and Adaptive Defense Systems
• Innate nonspecific, responds immediately,
  reduces workload of adaptive
• Adaptive specific, attack against particular
  invader, must be primed, slower but precise
• Immunity highly specific resistance to disease

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Innate Body Defenses

• Refers to barriers that cover body, cells and
  chemicals that act on initial front to protect
  from pathogens
• Nonspecific doesnt distinguish between
  bacteria, virus, fungus, etc.

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Innate Body Defenses Surface Membrane Barriers

• First Line of Defense
• Skin and mucous membranes
• Intact, keratinized epidermis physical barrier
• Mucous membranes line cavities open to
  exterior, physical barriers and secretions
• Acidic pH of skin secretions (pH3-5) inhibits
  bacterial growth, vaginal secretions acidic
• Stomach mucosa secretes HCl and protein-digesting
  enzymes
• Saliva and lacrimal fluid contain lysozyme
• Sticky mucous traps organisms in digestive and
  respiratory tracts
• Structural elements mucous coated cilia,
  respiratory

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Innate Body Defenses Internal Cells and Chemical

• Second line of Defense
• Phagocytes and NK cells destructive
• Inflammatory Response
• Chemical Substances that kill bacteria and help
  repair tissue
• Fever

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Phagocytes

• Macrophage or neutrophil engulfs foreign particle
• Flowing cytoplasmic extensions bind and pull
  inside, enclose in vacuole
• Vacuole fused with lysosome, digested

Figure 12.7
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Natural Killer Cells

• Police blood and lymph
• T cell lymphocyte, unique
• Can lyse and kill cancer and viral infected cells
  before adaptive arm enlisted
• Not specific, recognize any target by recognizing
  certain sugar on surface and lack of self
  molecules
• NOT phagocytic release lytic chemical called
  perforin

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Inflammatory Response
Increase blood flow to area
Chemotaxis
Plasma leakage from blood
Figure 12.8
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What is the purpose of inflammation?

• Prevents spread of pathogen
• Phagocytosis of pathogen
• Clotting proteins, wall off area, contain and
  repair
• Disposes of cell debris and pathogens
• Neutrophils via diapedesis, enter tissue drawn by
  positive chemotaxis
• Engulf dead damaged cells
• Monocytes -gt macrophages follow neutrophils
• May see third line of defense if contained
• Sets stage for repair
• Heat increase cellular metabolism, speeds
  defenses and repair

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Antimicrobial Proteins - Complement

• 20 plasma proteins circulate in blood inactive
• Bind sugars or proteins on foreign cells surface
  (Ab)
• One result is MAC membrane attack complex
• Amplify inflammation response chemicals
• Vasodilators
• Chemotaxis chemicals
• Foreign cells sticky (opsonization)

Figure 12.10
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Antimicrobial Proteins - Interferon

• Viral infected cells release small proteins
  called interferons
• Diffuse to nearby cells and bind to membrane
  receptors
• Stimulates synthesis of proteins that interfere
  with ability of viruses to multiply within the
  cell

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Fever

• Temp regulated by hypothalamus
• Pyrogen chemicals secreted by WBC and macrophages
  exposed to pathogens trigger increase in temp
• Mild to moderate benefit body
• Bacteria need Zn and Fe to replicate, during
  fever spleen and liver take up
• Increases metabolic rate of tissue cells, repair

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Adaptive Body Defenses

• Very specific immune response
• Requires initial exposure to prime immune
  cells, more vigorous response second time
• Third Line of Defense
• Protects from many pathogens
• Protects from damaged, mutated self cells
• Failure leads to diseases such as
• Cancer
• RA
• AIDS

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Adaptive Body Defenses

• It is antigen specific acts/recognizes specific
  invaders
• It is systemic immunity not restricted to
  initial site of infection
• It has memory recognizes and mounts stronger
  attacks after initial introduction
• Depends on cells ability to recognize foreign Ag
  and communicate with each other to mount
  effective response
• 2 components
• Humoral Immunity Antibody
• Cell Mediated Immunity Cellular

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Antigens

• Ag any substance that is capable of mobilizing
  our immune system and provoking an immune
  response
• Mostly nonself
• Proteins, nucleic acids, carbohydrates, lipids
• Proteins strongest Ag
• Something is antigenic because surface bears
  these molecules
• Self cells also have these molecules
• During maturation, lymphocytes are exposed to
  self molecules and dont recognize as foreign
• Highly antigenic to others though organ
  donation, grafts!

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Cells of Adaptive DefenseLymphocytes

• T cells and B cells
• Originate in red bone marrow
• When released identical, differentiation depends
  on site of immunocompetent

Figure 12.11
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T cells

• Immunocompetent in thymus
• Maturation takes 2-3 days, directed by thymosin
• Divide rapidly
• Only those recognize foreign Ag survive
• Those recognize self-antigens destroyed
• Self tolerance part of education of lymphocytes

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B cells

• Immunocompetent in bone marrow
• Divide rapidly
• Only those recognize foreign Ag survive
• Those recognize self-antigens destroyed
• Self tolerance part of education of lymphocytes

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Immunocompetent Lymphocytes

• Immunocompetent lymphocyte only able to recognize
  1 Ag
• All receptors on lymphocyte surface recognize
  same Ag
• Become immunocompetent before meeting antigen
• Genes dictate receptors on lymphocyte surface not
  antigens
• Many types of lymphocytes will never be needed.
• Migrate to lymph nodes and spleen, meet Ag,
  complete maturation process
• Circulate through body (especially T cells)

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Macrophages

• Monocyte formed in bone marrow
• Big eaters in innate defense
• Antigen presenters to lymphocytes
• Secrete cytokines (proteins)
• Activated T cells release chemicals cause
  macrophages to become killer macrophages
• Remain fixed in lymphoid tissue

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Humoral (Ab-mediated) Immune Response

• Immunocompetent, but immature B cell Ag binds
  receptors on surface, activates, clonal selection
• Clonal Selection growth and division of B cell
  producing many copies of cells exactly the same,
  Ag-specific receptors
• Clone generation - 1 humoral response

Figure 12.12
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Humoral Immune Response

• Most clones become plasma cells
• Lag period
• 2000 Ab/sec
• Production lasts 4-5 days
• Ab levels peak at 10 days post contact, decline
• Some Memory Cells
• Immunological memory
• 2 humoral response
• Produced much faster (2Hrs), more effective
• Peak 2-3 days, levels remain high weeks to months

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Primary vs. Secondary Response
Figure 12.13
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Active vs. Passive Humoral Immunity

• Active Immunity production of Ab against Ag
• Naturally acquired during infection, develop
  signs or symptoms of infection
• Artificially acquired vaccines
• Spare from symptoms of disease
• Weakened Ag
• Both prime the immune system for next exposure

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Active vs. Passive Humoral Immunity

• Passive Immunity
• Ab from serum of an immune human or animal donor
• When?
• B cells not challenged by Ag, no memory
• Naturally mother to baby in breast milk
• Artificially Immune serum or gamma globulin
  (hepatitis)
• Antivenom snake bites
• Antitoxin botulism, rabies, tetanus
• Both of these will kill someone before active
  immunity

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Active vs. Passive Humoral Immunity
Figure 12.14
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Antibodies or Immunoglobulins (Igs)

• Soluble proteins secreted by B cells and plasma
  cell offspring in response to Ag
• 5 classes
• Basic structure
• 4 polypeptide chains
• Linked by disulfide bonds
• 2 light, 2 heavy chains
• Variable region Ag binding site
• Constant region determines class, roles in
  body, cells and chemicals can bind

Figure 12.15
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Antibody Classes
Table 12.2
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Antibody Functions

• Compliment fixation main Ab ammunition against
  cellular Ag, bacteria or mismatched blood cells,
  triggers lysis
• Neutralization Ab bind exotoxins or viruses,
  block harmful effects
• Agglutination more than one binding site, Ag-Ab
  complexes of cellular Ag, mismatched blood, blood
  typing
• Precipitation Ag-Ab complexes of soluble
  antigenic material
• Agglutination and precipitation easier to catch

Figure 12.16
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Cell-Mediated Immune Response

• Immunocompetent T cells activated by exposure to
  Ag
• Must be presented Ag by antigen presenting cell
  like macrophage
• 2 components to presentation
• Antigen
• Self protein on surface of cell

Figure 12.17
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Types of T cells Cytotoxic T cells

• Kill virus infected, cancer, foreign graft cells
• Bind to foreign cell
• Release toxic chemicals
• Granzymes
• Perforins

Figure 12.18
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Types of T cells Helper T cells

• Directors
• Interact with Ag bound B cells, stimulate faster
  division, Ab production
• Cytokine release
• Stimulate Cytotoxic T cells, B cells
• Attracting WBCs Neutrophils
• Enhance phagocytic activity of macrophages

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Types of T cells Regulatory T cellsand Memory
Cells

• Regulatory T cells
• Suppress activity of T cells and B cells
• Memory T cells
• Immunological memory

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Table 12.3 (1 of 2)
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Table 12.3 (2 of 2)
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Figure 12.19
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The End