Lymphatic System:
Structures & Immune
Response
Honors Anatomy & Physiology
Wbc engulfs bacteria:
http://www.youtube.com/watch?v=Jn
lULOjUhSQ
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
Lymph Vessels
•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
Lymphatic Vessel Drainage
What is elephantiasis?
Lymphatic ducts get
clogged with parasitic
roundworms
 Swelling of lower limbs
and scrotum due to
edema
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Filters lymph fluid
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Help activate the immune
system
◦ Macrophages destroy
microorganisms
◦ Lymphocytes monitor & attack
antigens
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100’s of these small organs
Bean shaped
<1inch long
Cortex (outer region)

Medulla (inner region)

Fewer efferent lymph vessels
than afferent vessels
◦ Dividing B cells
◦ Circulating T cells
◦ Plasma cells
◦ macrophages
Lymph Nodes

Spleen – monitors blood

Thymus – T cells become
◦ Red pulp -extracts aged & defective
blood cells
◦ Stores hemoglobin & platelets
(recycled)
◦ White Pulp -contains lymphocytes &
macrophages
immunocompetent (specific)
◦ Atrophy after puberty (replaced by
adipose tissue)
◦ Does not directly fight pathogens

Tonsils – invaginations trap
pathogens
◦ Contains lymphocytes & macrophages
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Palatine tonsils
Lingual tonsils
Pharyngeal tonsil
Tubal tonsils
Lymph Organs
MALT: Mucosa Associated
Lymphatic Tissue
 Protects passages open to exterior
 Produces memory cells against
invaders
 Includes:
◦ Peyers Patches

 Clusters of lymph tissue on small
intestine
◦ Appendix
 Off shoot of large intestine
 Destroys any bacteria may leave
intestine
Lymphatic Tissues

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

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
(20 Defense)

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
Innate (Non Specific) Defenses

Must be primed by initial exposure before it
can defend against it
3 important features:
 Specific against a particular pathogen
 Systemic – 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
Adaptive Defenses (Specific)

Antigens – Foreign substances
that provoke an immune response
◦ Non-self - not normally found in the
body
◦ Cause proliferation of lymphocytes &
antibodies

Antigens
Self-Antigens
◦ MHC (major histocompatibility
complex) proteins on surface of “self”
cells
◦ Variety - genetically determined
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AKA immunoglobulin (Igs)
Secreted by B cells or plasma cells
Structure:
◦ ‘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
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Inactivates pathogens and tags for
destruction
Antibodies
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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
Humoral Immune Response
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)
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How do Vaccines work?
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T cells mature in Thymus
Targets infected cells, cancer cells,
foreign tissues
Helper T cells (CD4)
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Cytotoxic T cells (CD8)
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Regulatory T cells
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Memory T cells
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Double recognition on an antigen
presenting cell:
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◦ Stimulates production of cytotoxic T
cells and B cells, activates
macrophages, and releases cytokines
(chemicals that trigger proliferation and
inflammation)
◦ Binds to infected cells and inserts
chemicals causing apoptosis
◦ Suppresses immune activity
◦ Responds quickly to subsequent
infections (last years)
◦ Non self antigen
◦ MHC proteins indicating “self” cell
Cell Mediated Response

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
Types of immunity
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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 pairs
Either choice should include: B cells, plasma
cells, antibodies, helper T cells, cytotoxic T
cells, memory cells, suppressor (regulator) T
cells, and macrophages
Select your Task…