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Lymphatic System:Structures & Immune
ResponseHonors Anatomy & Physiology
Wbc engulfs bacteria: http://www.youtube.com/watch?v=JnlULOjUhSQ
Lymph Vessels
Lymphatic vessels – drainage of excess interstitial fluid (lymph) that is returned to blood vessels
Lymphatic capillaries weave between tissue cells and blood capillaries in areolar tissue
Very permeable◦ Lacteals – specialized
capillaries found in villi of intestinal mucosa to help absorb fats
Flows to collectively larger vessels
Lymphatic Vessel Drainage
•Right lymphatic duct• Right arm, side of head
and upper thorax
• Empties into the right subclavian vien
•Thoracic duct• Much larger• Rest of the body
• Empties into junction of left subclavian vein & jugular vein
•About 3L enters blood every 24 hours
What is elephantiasis?
Lymphatic ducts get clogged with parasitic roundworms
Swelling of lower limbs and scrotum due to edema
Lymph Nodes
Filters lymph fluid◦ Macrophages destroy
microorganisms Help activate the immune system
◦ Lymphocytes monitor & attack antigens
100’s of these small organs Bean shaped <1inch long Cortex (outer region)
◦ Dividing B cells◦ Circulating T cells
Medulla (inner region)◦ Plasma cells◦ macrophages
Fewer efferent lymph vessels than afferent vessels
Lymph Organs
Spleen – monitors blood◦ Red pulp -extracts aged & defective blood
cells◦ Stores hemoglobin & platelets (recycled)◦ White Pulp -contains lymphocytes &
macrophagesThymus – T cells become immunocompetent
(specific)◦ Atrophy after puberty (replaced by adipose
tissue)◦ Does not directly fight pathogens
Tonsils – invaginations trap pathogens◦ Contains lymphocytes & macrophages
Palatine tonsils Lingual tonsils Pharyngeal tonsil Tubal tonsils
Lymphatic Tissues
MALT: Mucosa Associated Lymphatic Tissue
Protects passages open to exteriorProduces memory cells against
invadersIncludes:
◦Peyers Patches Clusters of lymph tissue on small
intestine◦Appendix
Off shoot of large intestine Destroys any bacteria may leave
intestine
Innate (Non Specific) Defenses
1st line defense- Surface Barriers: ◦Skin & Mucous Membranes Physical barrier Acidity of skin secretions
(ph 3-5) Sebum – toxic to bacteria HCl of stomach Saliva & lacrimal fluid
contain lysozyme◦Enzyme destroys bacteria
Mucus traps microorganisms
Innate (Non Specific) Defenses (20 Defense)
Cells◦Phagocytes – engulfs & digests
Macrophages from WBC monocytes◦Free (mobile) or fixed (liver, brain)
Neutrophils (WBC)◦Become phagocytic after encounters
pathogen◦Destroy self in process
Eosinophils (WBC)◦defend against parasitic worms
◦Natural Killer (NK) Cells “police” blood & lymph Detect lack of “self” antigens Direct contact induces target cell to
undergo apoptosis Lyse & kill cancer cells & viral infected
cells
Innate (Non Specific) Defenses
Chemicals◦ Inflammation -Prevents spreading of pathogen &
disposes pathogens & cell debris Redness & heat
◦Mast cells release histamines causing vasodilatation Swelling & pain
◦ Increased permeability of capillaries ◦Clotting factors, antibodies & fluid leak into tissues
◦Antimicrobial proteins Interferons (IFNs)
◦Secreted by viral infected cells to prevent other cells from becoming infected
◦Stimulate synthesis of proteins that interfere w/viral protein synthesis (not specific)
◦Fever Response to widespread infection Macrophages and WBC release pyrogens
◦Chem that resets thermostat in Hypothalmus◦ Increases metabolism
Adaptive Defenses (Specific)
Must be primed by initial exposure before it can defend against it
3 important features:Specific against a particular pathogenSystemic – not restricted to infection site
◦Humoral Immunity – circulating antibodies in body fluids
◦Cell Mediated Immunity – lymphocytes attack pathogens
Memory – recognizes and mounts strong attacks against previously encountered pathogens
Antigens
Antigens – Foreign substances that provoke an immune response◦ Non-self - not normally found in the
body◦ Cause proliferation of lymphocytes &
antibodiesSelf-Antigens
◦ MHC (major histocompatibility complex) proteins on surface of “self” cells
◦ Variety - genetically determined
Antibodies
AKA immunoglobulin (Igs)Secreted by B cells or plasma cellsStructure:
◦ ‘Y’ shaped; 4 polypeptide chains (2 Heavy, 2 Light)◦Variable region – 2 binding sites that responds to
specific antigens◦Constant region – determines Ig class
Antigen-antibody complex:◦Neutralizes - no longer harmful◦Agglutination – cross linked causing clumping
Inactivates pathogens and tags for destruction
Humoral Immune Response
Antigen binding to receptor on specific B lymphocyte stimulates proliferation forming clones that differentiate into:
Plasma cells – secrete 2,000 antibodies per second (for about 5 days then dies)!!!
Memory cells – will respond to subsequent exposures to same antigen
How do Vaccines work?
Contain dead or attenuated (weakened) pathogens or their components
Spares us symptoms of disease that would normally occur during a primary response
Memory cells are formed against antigen (humoral only)
Cell Mediated Response
T cells mature in Thymus Targets infected cells, cancer cells,
foreign tissues Helper T cells (CD4)
◦ Stimulates production of cytotoxic T cells and B cells, activates macrophages, and releases cytokines (chemicals that trigger proliferation and inflammation)
Cytotoxic T cells (CD8)◦ Binds to infected cells and inserts
chemicals causing apoptosis Regulatory T cells
◦ Suppresses immune activity Memory T cells
◦ Responds quickly to subsequent infections (last years)
Double recognition on an antigen presenting cell:◦ Non self antigen◦ MHC proteins indicating “self” cell
Types of immunity
Innate – genetically determined
Acquired – arises during life ◦Active – appears after exposure to antigen
Naturally- continually induced as encounter “new” pathogens or antigens
Induced – stimulated under controlled conditions◦Vaccine: dead/inactive pathogen that induces an immune
response
◦Passive – transfer of antibodies from another source Naturally – mother to baby
◦Gestation – via placenta◦ Infancy – via breast milk
Induced – antibodies administered to fight infection or prevent disease after exposure
Select your Task…
Create a comic strip depicting the specific response of lymphatic system (combating a pathogen of your choice)
Write a script for a mini-play describing specific response of lymphatic system
May work in pairsEither choice should include: B cells, plasma
cells, antibodies, helper T cells, cytotoxic T cells, memory cells, suppressor (regulator) T cells, and macrophages