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Lymphatic System
Chapter 12: Body Defenses
Two part system:
• 1. lymphatic vessels: transport fluids
that have escaped from the circulatory
system back to blood vessels.
• 2. lymphoid tissue and organs: make
and store lymphocytes and phagocytes
which are important in body defense.
Lymph Vessels
• Interstitial fluid (AKA lymph): fluid
that surrounds tissues and cells.
• Most of this fluid comes from the blood
in the capillaries that is forced out
taking nutrients with it.
• If this fluid is not returned to the
capillary blood then blood volume will
decrease…and that is bad!!!!
• As much as 3L per day soak our
tissues and that’s a lot!
Lymph Vessels
• Edema: fluid accumulation; too much
fluid reduces the amount of nutrient
exchange with cells. BAD!!!
• So in come the lymph vessels to save
the day!
• Just like blood vessels, the lymph
vessels taper to capillaries called …
lymph capillaries.
Lymph Vessels
Lymph capillaries
• Dead end vessels
• Flow toward heart
• Flap-like minivalves that open when there
is low pressure internally (lots of
interstitial fluid) and close with high
internal pressure.
• Large enough openings to allow large
proteins, bacteria and viruses to diffuse
into the vessel.
Lymph Vessels
• Lymph capillaries  larger lymph
vessels  lymphatic collecting vessels
 lymphatic duct
• Right lymphatic duct: drains from the
right arm, head and thorax into the
right subclavian vein.
• Thoracic duct: drains from the rest of
the body into the left subclavian vein.
Lymphatic Vessels
• No heart pump like the cardiovascular
• BUT…
– Uses one way valves,
– Muscular pumps (skeletal muscles),
– The respiratory pump,
– And smooth muscles push lymph through
large vessels.
Lymph Nodes
Lymph Nodes
• Remove foreign substances like
bacteria, viruses and cancer cells.
• Produce lymphocytes: type of white
blood cell that produce antibodies.
• House macrophages: type of white
blood cell that eat bacteria and such.
• Lymph node swelling is the result of
the increased production of wbc and
trapping the foreign objects.
Lymph Nodes
• Cluster along lymph vessels (See page
371 figure 12.3)
• Kidney shaped
• Less than one inch long
• Surrounded by a capsule.
• Trabeculae strands branch off the
capsule and compartmentalize the
Lymph Nodes
Lymph Nodes
• Cortex: outer area
– Follicles filled with T-lymphocytes (T-cells)
– Germinal centers filled with Blymphocytes that produce plasma cells
which release antibodies
• Medulla: central area
– House the phagocytic macrophages (cell
Lymph Nodes
• Afferent vessels: flow towards the
node; enter at the convex side; there
are many of them
• Efferent vessels: flow away from the
node; out the concave side (called the
hilus); there are few of them.
• Flow through the node is slow allowing
the filtering process to complete.
Other Lymph Organs
• Lymph nodes: one type of lymph
organ…but there’s more!
• All lymph organs have two things in
common: reticular connective tissue
and lymphocytes.
Examples: spleen, thymus, tonsils,
Peyer’s patches (MALT)
Other Lymph Organs
a. on the left side of the stomach
b. Filters blood of bacteria, viruses, and
debris (unlike the liver)
c. Act as blood reservoir (like the liver)
d. Destroy old erythrocytes and recycle
e. Store platelets
f. Produce lymphocytes
Other Lymph Organs
a. covered in chapter 9 as an
endocrine gland
b. found low in the throat by the heart
c. produces hormones like thymosin
that program certain lymphocytes
Other Lymph Organs
a. lymph tissue that surrounds the pharynx
(back of throat).
b. “air filter” trap bacteria and debris that
enters the throat.
c. can become congested with bacteria
and inflamed
Other Lymph Organs
a. tonsils for the intestines
b. many are found in the small intestine
c. capture and destroy bacteria like the
tonsils with macrophages
d. MALT (mucosa-associated lymphatic
tissue) tonsils and Peyer’s patches
Peyer’s Patches
Body Defenses
Two systems of defense
(a broad overview)
• 1. nonspecific defense system
– First line of defense
– Responds immediately & to all foreign
substances (no questions asked!)
– Defenders include: intact skin, mucous
membranes, inflammatory responses, and
some specific blood proteins.
Body Defenses
• 2. specific defense system
(AKA immune system)
– Second line of defense
– Not quick, but very specific (must be invaded
by pathogen, antigen, then produce a specific
antibody to attack).
– Attack invaders like pathogens as well as
transplants, grafts, and sometimes our own
selves (autoimmune disease)
– Defenders include: cells like lymphocytes and
macrophages and chemicals like antibodies
Nonspecific Body Defenses
See table 12.1
• 1. surface membrane barriers
(mechanical barrier)
– Skin (lines the outside of us) and mucous
membranes (lines the inside of us;
respiratory, digestive, urinary tracts)
– Acidic pH, toxic chemicals and enzymes
• 2. cells and chemicals
– Phagocytes, natural killer cells,
inflammation, bacteriotoxins, and fever
Nonspecific Body Defenses
Cells and Chemicals
A. phagocytes (cell eater): like
macrophages and neutrophils
Nonspecific Body Defenses
Cells and Chemicals
• B. Natural (born) killer cells: in blood
and lymph that lyse (slice and dice)
virus-infected body cells and cancer
– Recognize sugars on membranes of bad
– Release chemicals that digest plasma and
nuclear membranes.
– No antibodies and no phagocytosis!
Nonspecific Body Defense
Cells and Chemicals
C. Inflammatory response (see page 375)
• Steps for inflammation –
– 1. injury (trauma, burn, cut, infection)
– 2. chemical ALARM sent out (histamines and
kinins are released by the injured cells)
– 3. blood vessels dilate bringing more blood
(heat and redness)
– 4. capillaries leak plasma (swelling and pain)
– 5. this brings lymphocytes and phagocytes to
the area
Nonspecific Body Defense
Nonspecific Body Defense
Awesome things the
response brings to
• Prevents the spread
of disease
• Gets rid of damaged
cells and pathogens
• Prepares the tissue
for repair
Nonspecific Body Defense
Cells and Chemicals
D. Antimicrobial Chemicals:
1. Complement proteins – about 20
different proteins that float around in
the blood plasma attaching
themselves to the membranes of
foreign bodies.
a) Effects include: osmotic explosion,
vasodilation, chemotaxis, opsonization
Nonspecific Body Defense
Cells and Chemicals
D. Antimicrobial Chemicals:
2. Interferons – virus infected cells send
out interferons to bind to the
membrane proteins of other, noninfected cells, that new viruses would
attach to.
Nonspecific Body Defense
E. Fever: moderate temperature
elevations are helpful in two ways, but
extreme temperature elevations cause
damage to even healthy tissue by
denaturing their proteins.
– Lessens Fe and Zn needed for bacterial
– Increases metabolic rates and tissue
Specific Body Defenses
• 1st line of defense is the membrane
barrier (skin and mucous membranes)
• 2nd line of defense are nonspecific cells
and chemicals (killer cells, phagocytes,
compliment and interferon proteins)
• 3rd line of defense is the immune
Specific Body Defenses
Some Definitions:
1. Antigens: any foreign molecules, including,
but not limited to, foreign proteins, nucleic
acids, many carbohydrates, some lipids and
things with these chemicals on them like
bacteria, pollen, viruses, etc.
2. Haptens: small, “incomplete” antigens found
in allergens like poison ivy, animal dander,
3. Antibodies: “factors”, usually proteins, that
attack antigens.
Specific Body Defenses
• Three important aspects of the immune
1. It is antigen specific
2. It is systemic
3. It has a “memory”
Specific Body Defenses
Two arms of the immune system
1. Humoral (antibody-mediated) immunity:
Antibodies are chemicals found in the humors
(fluid) of the body…produced by B lymphocytes
2. Cellular (cell-mediated) immunity:
The lymphocytes themselves…T lymphocytes
Before we get into more details of each of these
two arms let’s look at the major cells involved.
Specific Body Defenses
Lymphocytes: arise from hematocytes
• T cells become immunocompetent in
the thymus (cell-mediated)
• B cells become immunocompetent in
the bone marrow (antibody-mediated)
• Immunocompetent = becoming
competent or capable of responding to
a specific antigen by bonding to it.
Specific Body Defenses
Specific Body Defenses
• Immunocompetent lymphocytes are
antigen specific which means they can
attach to one and only one antigen.
• “It is our genes, not antigens, that
determine what specific foreign
substances our immune system will be
able to recognize and resist.”
• They migrate through the lymph and
blood system and “hide and wait” where
they may or may not be used.
Specific Body Defenses
Macrophages: arise from monocytes
• work in one of three ways…
1. Put fragments of engulfed antigens on
their membrane to help T cells
recognize them.
2. Secrete proteins called monokines
that stimulate T cells and cause fever.
3. Become “killer macrophages” via T
cell activation.
Specific Body Defenses
Back to the two types of immune
1. Humoral (antibody-mediated)
– Antibodies are chemicals found in the
humors (fluid) of the body…produced
by B lymphocytes
2. Cellular (cell-mediated) immunity:
– The lymphocytes themselves…T
Specific Body Defenses
Primary humoral response (AKA Cloning)
1. Antigen binding activates B cells.
2. Clonal selection: rapid multiplication of the
cell with the same antibody on its surface.
3. Most cells lose their membrane antibodies* to
become plasma cells that die within a few
4. Some cells keep their membrane antibodies
to become memory cells that live forever
Specific Body Defenses
Secondary humoral response
1. Memory cells await another meeting
with the same antigen.
2. The same steps happen, but…
3. The next meeting is faster, longer
lasting, and much more effective
(often you don’t even know you have
been infected again).
See page 382 & 383
Specific Body Defenses
• Active and passive humoral immunity
1. Active immunity
a. Naturally acquired via bacteria/virus
b. Artificially acquired via vaccine
2. Passive immunity
a. Naturally acquired via mother and child
b. Artificially acquired via immune serum or
gamma globulin.
Specific Body Defenses
• Keep us from
experiencing the
trauma of the
• Boost the
secondary immune
Specific Body Defenses
• Immune serum is used as…
– Antivenom (snake venom)
– Antitoxin (tetanus)
– Antirabies serum
– Monoclonal antibodies – commercially
prepared antibodies used for treating
cancer, diagnosing pregnancy, hepatitis,
rabies and
Specific Body Defenses
(immunoglobulins or Igs)
• Soluble proteins
secreted by B cells and
bind with specific
• There are 5 classes of
• Two identical halves
Antibody/Antigen Complex
Immunoglobin Classes:
Immunoglobin Classes (p386)
• IgM: (pentamer) first to be released in
primary response
• IgA: (dimer) protects mucus lining from
• IgD: (monomer) activates B cells
• IgG: (monomer) major participant in
primary and secondary response; crosses
• IgE: (monomer) primary inflammatory and
allergenic responder
Antibody Functions
1. Complement
2. Neutralization
3. Agglutination
4. Precipitation
Antibody Function
1. Compliment
– Chief source of
antibody used
against cellular
antigens (discussed
in nonspecific body
defenses pgs 376377)
– Causes lysing of
foreign cells via
Antibody Function
2. Neutralization
• Neutralizes viruses
or bacteriotoxins by
“hiding” them.
• The antibodies
surround the target.
• This makes it easy
pickings for
Antibody Function
3. Agglutination
• Cross-linking of cell
• Causes clumping of
foreign cells
• Seen mainly in blood
• Macrophages can
gobble them up
Antibody Function
4. Precipitation
• Same as agglutination, but instead of
cross-linking cells it cross-links soluble
• This makes them insoluble and
precipitate out of solution
• Now macrophages can slurp them up
like frosting! <3 
Specific Body Defenses
Back to the two types of immune
1. Humoral (antibody-mediated)
– Antibodies are chemicals found in the
humors (fluid) of the body…produced by
B lymphocytes
2. Cellular (cell-mediated) immunity:
– The lymphocytes themselves…T
Specific Body Defenses
Immune Response
• T cells
• Can’t bind with
antigens on their
• They must be helped
by macrophages via
antigen presentation
Specific Body Defenses
Produces different types of mature T cells
1. Cytotoxic (killer) T cells: kill virus infected
cells, cancer cells and graft cells by injecting
toxins like perforin.
2. Helper T cells: “boss” lymphocytes
3. Suppressor T cells: suppress lymphocyte
activities at the end of an attack.
4. Delayed hypersensitivity T cells: major player
in cell-mediated allergy and chronic
inflammation. (IgE is the antibody-mediated
1. Autografts: tissue grafts from the
same person
2. Isografts: tissue grafts from an
identical twin
3. Allografts: tissue grafts from an
unrelated person (most common
4. Xenografts: tissue graft from another
species (never successful-?-)
Organ Transplant/Rejection
Allografting is tricky…
a. Match ABO blood group
b. Match other blood antigens
c. Match cell membrane antigens of the
specific tissue being transplanted;
must have at least 75% matching.
d. Receiving immunosuppressive
therapy treatments (severe side
effects; easily mortally infected)
Disorders of Immunity
Three main types of immune
• Allergies
• Immunodeficiencies
• Autoimmune disease
Disorders of Immunity
Allergies (“paranoia”)
• Tissue damage caused by an
overactive immune response of a
“perceived” threat.
• Allergen: “special” type of antigen
• Two main types of allergic reactions
– Immediate (acute) hypersensitivity
– Delayed hypersensitivity
Disorders of Immunity
Immediate (acute) hypersensitivity
• Antibody-mediated response (B cells)
• IgE antibodies attach to mast cells
(histamine holding cells) releasing
histamines (inflammation).
• Symptoms like: runny nose, watery
eyes, bronchiole contraction
• Use antihistamines to control.
Disorders of Immunity
Anaphylactic shock
• Similar to immediate hypersensitivity,
but more widespread and rapid.
• Allergen is run through the blood
stream (insect sting or bite, medicine
like penicillin)
• Epinephrine is used instead of
• Life threatening
Disorders of Immunity
Delayed hypersensitivity
• Cell-mediated response (T cells)
• After a few days cytotoxic T cells
release lymphokines that cause skin
• Use corticosteroid drugs to control
• Poison ivy, smellies, ect.
Disorders of Immunity
• Low immune function
• Examples include:
– Severe combined immunodeficiency
disease (SCID) where the immune system
is so compromised even the slightest
disease is a killer… bubble kid syndrome.
– Acquired immune deficiency syndrome
(AIDS) where HIV attack Helper T cells to
compromise the immune system.
Disorders of Immunity
Autoimmune disease
• The immune system goes rogue,
attacking self-antigens as well as
foreigners; this causes damage to
• Examples include (p396):
Multiple sclerosis
Juvenile diabetes
Rheumatoid arthritis