Download Lymphatic System

Lymphatic System
• Why do we study the lymphatic
system?
• Why is it important to us?
Seeing your immune system
• When you get a cut…all sorts of bacteria and
viruses enter your body through the break in
the skin.
• When a mosquito bites you, you get a red,
itchy bump.
• You inhale thousands of germs (bacteria and
viruses) that are floating in the air.
• Each day you eat hundreds of germs
• Allergies
• Organ Transplants
Functions of the Lymphatic System
Not only….
• helps defend the body against diseasecausing agents
But also….
• absorbs fats
•
transports excess fluid to the bloodstream
What makes up the Lymphatic
System?
First Line of Defense:
• Skin
– Primary boundary between germs and your body
– Secretes antibacterial substances
• Nose, Mouth, and Eyes
– Tears contain an enzyme that breaks down the cell
wall of many bacteria
– Saliva is antibacterial
– Nasal passages and lungs are coated in mucus, so
many germs not killed immediately are trapped in
the mucus and swallowed.
And then also the…..
•
•
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Lymph System
Thymus
Spleen
Malt
– Peyer’s patches
– Tonsils
– appendix
• Bone Marrow
• White Blood Cells
• Antibodies
Lymph System
• Closely resembles the Circulatory System
• One way system
• Composed of:
Lymph Capillaries
Lymph Vessels
Lymph Nodes
Lymphatic trunks and ducts
But first….What is lymph?
• Lymph is simply
tissue fluid that has
entered the lymphatic
system
• Lymph formation
prevents the
accumulation of
excess tissue fluid, or
edema
LYMPH
• A clearish liquid that bathes the cells with
water and nutrients; basically, blood
plasma – the liquid that makes up the
blood minus the red and white cells.
• Blood transfers food, water, hormones,
and oxygen to the lymph through the
capillary walls, and lymph carries it to the
cells.
• The cells produce proteins and waste
products and the lymph absorbs these
products and carries them away.
• Proteins, bacteria and virus are prevented
from entering blood capillaries but easily
enter the lymph capillaries
Why is this a problem?
Bacteria and viruses can then use
the lymphatic system to spread
throughout the body
How does lymph move?
•
•
The lymphatic system does not have a pump
like the circulatory system.
Lymph is transported by:
1. Milking action of the skeletal muscles
2. Pressure changes during breathing
3. Smooth muscle contraction
•
Any interruption in lymph flow can result in
edema
Lymphatic System Pathway
Lymphatic Capillaries
• Microscopic closed
ended tubes that
weave between
tissue cells, blood
capillaries and
connective tissue
• Walls are very
similar to blood
capillaries
The lymphatic capillaries
lead
to lymphatic vessels
Lymphatic Vessels
• Very similar to veins but thinner
• Have valves that prevent backflow
Lymphatic Vessels
lead to
specialized organs called
lymph nodes
Lymph Node
• Kidney-bean
shaped
• Less than one inch
long
• Buried in
connective tissue
• 500-600 are located
along the lymphatic
pathways
• Afferent lymphatic
vessels lead to the
lymph node
• Efferent vessels
lead out of the
node
What is the function of
lymph node?
• Filter harmful particles from lymph before
returning it to the bloodstream
• When fighting certain infections, the lymph
nodes swell with bacteria AND the cells
fighting the bacteria….yes, this is why you
can feel them when you are sick.
• Swollen lymph nodes are good indication
that you have an infection.
• View the lymph nodes at work…..
Immune cells within
the lymph nodes
• B Lymphocyte
• T Lymphocyte
• Macrophages
Next
B Lymphocyte
• Originates in red bone
marrow
• Produce antibodies
• Surface of B Lymph is
covered with
receptors that acts as
a key to fit specific
antigens
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T Lymphocyte
• Originates in red
bone marrow and
matures in thymus
gland
• These cells kill other
cells that are
harboring a virus
• 2 types of
T lymphocyte
2 Types of T Lymphocytes
• Helper T cells
• Killer T cells
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Helper T cells
• Release proteins that
stimulate B cells to
produce antibodies
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Killer T cells
• Killer T cells kill
antigens on the spot
• Release chemicals
that bore into the
foreign cells
membrane and the
contents bursts out of
the hole and dies
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Macrophage
• White blood cells that continually search
for foreign molecules, viruses, or
microbes.
• When found, the macrophages engulfs
and destroys them.
Do you want to see one…..
Macrophage attacking E.Coli
Return
The efferent vessel
leading out of the lymph node
dumps into the
lymphatic vessel
that dumps into the
lymphatic trunk
Lymphatic Trunk
The Trunks
1.
2.
3.
4.
5.
Lumbar
Intestinal
Intercostal and bronchomediastinal
Subclavian
Jugular
The trunks
then join the
collecting ducts
Collecting Ducts
Two collecting ducts:
1. Thoracic duct – largest and
longest of the two ducts
2. Right lymphatic duct
The collecting ducts
then return
the lymph
back into the blood stream
by way of the
subclavian vein
And on to the other lymphatic organs…..
• Thymus
• Spleen
• MALT
– Peyer’s patches
– Tonsils
– Appendix
• Bone Marrow
Thymus Gland
• Located in the
chest between
the sternum and
the heart
• Soft, bilobed
• Larger in children
than in adults
What is the function of
the thymus gland?
• Responsible for the Maturation of T-cells
– T-cells are produced in the bone marrow but are
transported through the blood to the thymus where
they mature
– T-cells are a type of lymphocyte (WBC)
• Produces thymosin
– Thymosin is a hormone that encourages
lymphocyte production
Spleen
• filters blood like the lymph node filters
lymph
• filters foreign particles & damaged red
blood cells from the blood
• also stores blood that can be released
when needed
• You can live without it but makes you more
susceptible to infections
Peyer’s Patches
• found on the walls of
intestines
• filter out potentially
harmful bacteria that
might enter the
intestinal tract
Tonsils
Trap bacteria
before entering
body through
the nose and
mouth like
armed guards
1. Pharyngeal
2. Palatine
3. Lingual
Appendix
• not generally
credited with
significant function
BUT…..
• current evidence
tends to involve it in
the immunity
mechanism
Defense Against Infection
The Immune System
Functions of the Immune System
• Recognize invading microorganisms
• Respond to the organism and try to beat it
• Terminate the response as quickly as the
organism is eliminated so as to not
damage the host cell
Two types of defenses
INNATE IMMUNITY
Rapid responses to a
broad range of microbes
External defenses
Skin
Mucous membranes
Secretions
Invading
microbes
(pathogens)
ACQUIRED IMMUNITY
Slower responses to
specific microbes
Internal defenses
Phagocytic cells
Antimicrobial proteins
Humoral response
(antibodies)
Inflammatory response
Natural killer cells
Cell-mediated response
(cytotoxic
lymphocytes)
Next
Innate (nonspecific) Defenses
• Present from birth and fast acting
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Return
Species Resistance
Mechanical Barriers
Chemical Barriers
Fever
Natural Killer (NK) Cells
Inflammation
Phagocytosis
Species Resistance
• Each species is resistant to certain
diseases that may affect other species
but is susceptible to diseases other
species may resist.
Return
Mechanical Barriers
• Includes the skin & mucous
membranes lining passageways of the
respiratory, digestive, urinary, &
reproductive systems that prevent
entrance of some infectious agents.
• Prevention can occur as long as these
barriers remain intact.
Next
Return
•In the trachea, ciliated epithelial cells sweep
mucus and any entrapped microbes upward,
preventing microbes from entering the lungs
Chemical Barriers
• enzymes in gastric juice & tears kill some
pathogens
• low (acidic) pH in the stomach prevents
growth of some bacteria
• high salt concentration in perspiration kills
some bacteria
Return
Fever
• viral or bacterial infection stimulates
certain lymphocytes to secrete
endogenous pyrogen, which
temporarily raises body temperature
• higher body temperature & the
resulting decrease in blood iron level
production by the liver & spleen causes
an increase in phagocytic activity that
hampers infection
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Natural Killer Cells
• a group of lymphocytes that secrete
cytolytic perforins to destroy cells infected
by viruses & cancer
– Perforins destroy the cell membrane & enhance
inflammation
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Inflammation
• a tissue response to damage, injury, or
infection
• produces localized redness, swelling, heat, &
pain
• chemicals released by damaged tissues
attract white blood cells to the site
– in bacterial infection, the resulting mass of white
blood cells, bacterial cells, & damaged tissue may
form a thick fluid called pus
Next
Return
Phagocytosis
• neutrophils & monocytes are the most active
phagocytes in blood
– monocytes give rise to macrophages, which
remain in fixed tissues
• phagocytic cells associated with the linings
of blood vessels in the bone marrow, liver,
spleen, & lymph nodes constitute the
mononuclear phagocytic system
• phagocytes remove foreign particles from
tissues & body fluids
Next
Return
Acquired (specific) Immunity
Acquired, not present at birth
and
• slow initial reaction
• Also, referred to as adaptive defenses
• Second line of defense
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Important Definitions
• Antigen – any
substance
that when
introduced to
the body is
recognized
as foreign
and activates
the immune
system
• Antibody –
substance
produced by
the body that
can provide
immunity
against a
specific
antigen
Immunity
• resistance to particular pathogens
or to their toxins
“Self”
“Nonself”
Molecules that
are
part
of the body
Molecules that
are
foreign
to the body
Pathogen
• A disease causing
agent.
• Includes bacteria,
fungi, viruses, and
parasites.
Antibody-Mediated (humoral)
Immunity
• The defense method that uses antibodies,
developed from B cells, as the troops to go
into battle
Return
LE 43-19
Binding of antibodies to antigens
inactivates antigens by
Viral neutralization
(blocks binding to host
and opsonization increases
phagocytosis)
Agglutination of
antigen-bearing particles,
such as microbes
Soluble
antigens
Bacterium
Activation of complement system
and pore formation
Complement
proteins
Bacteria
Virus
Return
Precipitation of
soluble antigens
MAC
Pore
Foreign cell
Enhances
Leads to
Phagocytosis
Cell lysis
Macrophage
Cell-Mediated Immunity
• Immune reaction directed against body
cells that have been infected by viruses
and bacteria; controlled by T cells.
Return
Cell-mediated immune response
Humoral immune response
First exposure to antigen
Intact antigens
Antigens displayed
Antigens engulfed and
by infected cells
displayed by dendritic cells
Activate
Activate
B cells
Gives rise to
Plasma
cells
Memory
B cells
Secreted
cytokines
activate
Helper
T cell
Gives rise to
Active and
memory
helper
T cells
Secrete antibodies that defend against
pathogens and toxins in extracellular fluid
Activate
Cytotoxic
T cell
Gives rise to
Memory
cytotoxic
T cells
Active
cytotoxic
T cells
Defend against infected cells, cancer
cells, and transplanted tissues
Classification of Immunity
• Active
Immunity
• Passive
Immunity
Active Immunity
• Long-term immunity
• Exposure to disease
and survive –
naturally acquired
active immunity
• Vaccine containing
weakened or dead
pathogens –
artificially acquired
active immunity
Passive Immunity
• Short-term immunity
• Antibodies passed to
fetus or through
mother’s milk –
Naturally acquired
passive immunity
• Anti-serum or gamma
globulin – artificially
acquired passive
immunity
WHAT CAN GO WRONG
• If the delicate
balance of the
immune
system is
disrupted,
effects range
from minor to
often fatal
Autoimmune Diseases
• Occurs when your immune system attacks
your own “self” cells
• Some bacteria and viruses cause the T
cells to attack the body’s own cells.
• Killer T cells start to view other cells in the
body as foreign.
Tissue Transplants
• The immune system’s ability to distinguish self
from non-self limits tissue transplantation
• The immune system can wage war against
cells from other individuals
• Transplanted tissues are usually destroyed
by the recipient’s immune system
Blood Groups and Transfusions
• Antigens on red blood cells determine whether a
person has type A, B, AB, or O blood
• Antibodies to non-self blood types exist in the
body
• Transfusion with incompatible blood leads to
destruction of the transfused cells
• Recipient-donor combinations can be fatal or
safe
Rheumatoid
Arthritis
Autoimmune
disease leading
to damage and
inflammation of
joints
Other Autoimmune Diseases
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Systemic lupus erythematosus
Multiple sclerosis
Insulin-dependent diabetes
AIDS
Acquired Immunodeficiency
Syndrome (AIDS)
• People with AIDS are highly susceptible to
opportunistic infections and cancers that
take advantage of an immune system in
collapse
• Because AIDS arises from loss of helper T
cells, it impairs both the humoral and cellmediated immune responses
• The loss of helper T cells results from
infection by the human immunodeficiency
virus (HIV)
LE 43-22
The spread of
HIV is a
worldwide
problem
The best
approach for
slowing this
spread is
education
about
practices that
transmit the
virus 1 µm
Allergies
• Allergies are
exaggerated
(hypersensitive)
responses to antigens
called allergens
Allergies
• In localized allergies such as hay fever,
IgE antibodies produced after first
exposure to an allergen attach to
receptors on mast cells
• The next time the allergen enters the body,
it binds to mast cell–associated IgE
molecules
• Mast cells release histamine and other
mediators that cause vascular changes
leading to typical allergy symptoms
Immediate Reaction Allergy
LE 43-20
IgE
Allergen
Granule
Mast cell
Histamine
Anaphylactic Shock
• An acute allergic
response can lead
to anaphylactic
shock, a lifethreatening
reaction that can
occur within
seconds of
allergen exposure