The Lymphatic System and Body Defenses:

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The Lymphatic System and Body Defenses

• Death to the Invaders!

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Lymphatic System
Consists of two parts
-the lymphoid vessels
- the lymphoid tissue and organs
Function

• pick up plasma that has leaked out of blood
  vessels
• (called lymph) and return it to the bloodstream

• As nutrient, waste, and gas exchange occurs in
  the
• Capillaries some fluid leaks out

- Up to 3 liters per day leaks out
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Structural Relationship Between Blood and
Lymphatic Capillaries
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Lymph
Lymph blood plasma in the interstitial spaces
(spaces between cells)
- This fluid in referred to as lymph
- This fluid must be returned to the bloodstream
if not, edema will occur
- edema will prevent normal fluid exchange
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Functions of the Lymphatic System
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Lymph
Vessels that absorb lymph and carry it back to
the bloodstream
Lymph capillaries absorb fluid
This fluid must be returned to the bloodstream
if not it produces edema
Edema prevents normal fluid exchange
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Functions of the Lymphatic System
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Lymphatics
Vessels that absorb lymph and carry it back
to the bloodstream
Lymph capillaries absorb the interstitial fluid
Lymph is transported by a series of larger and
larger vessels
The right lymphatic duct and the Thoracic duct
empty into the subclavian vein
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Lymph Nodes
Lymph is filtered through lymph nodes as it
passes back to the bloodstream
Lymph nodes contain macrophages and lymphocytes
Bacteria, viruses, and foreign materials are
destroyed
When large numbers of bacteria or viruses are
trapped in the node, the node swells and becomes
painful
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Distribution of Lymph Nodes
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Lymphoid Organs
In addition to lymph nodes, the body
contains lymphoid organs that play a role in
protecting the body
However, only lymph nodes filter lymph
Lymphoid organs include
Spleen Thymus Tonsils Peyers patches
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Lymphoid Organs
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Spleen
Filters blood of bacteria, viruses, and other
debris
Most important function is to destroy worn out
red blood cells
Also stores platelets and red blood cells
It also produces lymphocytes
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Thymus, Tonsils, Peyers Patches
Thymus found in the thorax superior to the heart
Active only in the young
Functions in the production of lymphocytes
Tonsils found at the back of the throat
Trap and remove bacteria and viruses that enter
the throat
Peyers Patches found in the small intestine
They serve a similar function as do the tonsils
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Lymph Node Structure
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Body Defenses
Nonspecific defense system
- intact skin and mucous membranes

• inflammatory response rubor, dolor, calor,
  tumor,
• and loss of function

- These defenses prevent entry and spread of
organisms
Specific defense system the immune system
- attacks specific invading organisms
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The Immune System
- attacks specific foreign substances and
organisms
- most important immune cells are macrophage and
lymphocytes
- must be exposed to a substance before it can
protect against it
- produces immunity to diseases
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Nonspecific Defenses Surface Barriers
- skin and mucous membranes the first line of
defense
- Acidic secretions inhibit bacteria
- Lysozyme in saliva and tears destroys bacteria
- sticky mucous traps organisms
- stomach acid kills bacteria
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Nonspecific Defenses Cells
- Phagocytes
- engulf and destroy invading organisms
- They are present in every organ
Natural Killer Cells
- attack any foreign cell of substance (are
nonspecific)
- attack the cells membrane and destroys the cell
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Phagocyte Function
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Nonspecific Defenses Inflammatory Response Pt. 1
- The inflammatory response is considered the
second line of defense

• The five cardinal signs of inflammation are
• rubor, dolor, calor, tumor, loss of function

• injured cells release histamine. Kinins, and
  other
• Inflammatory chemicals. These chamicals

• cause vessels to dilate and capillaries to leak
• Activate pain receptors
• Attract phagocytes (called chemotaxis)

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Inflammatory Response Pt. 2 Three Main Functions
-
- prevent the spread of damaging materials
- dispose of cell debris and pathogens
- set the stage for repair
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Inflammatory Response Pt. 3 Disposal of Debris

• Neutrophils enter the inflamed area and begin
  disposing of
• damaged / dead cells and pathogens

Moncytes enter the area and begin phagocytes
(become macrophages)
- Macrophages pplay a major role in the disposal
of debris
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Inflammatory Response Pt. 4 Sealing off the area
- clotting proteins are activated and seal off
the area with fibrin
- This prevents the spread of pathogens
- fibrin serves as a scaffolding for permanent
repair
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Inflammatory Response Pt. 5 Conclusion
- localized heat speeds up the actions of the
inflammatory cells

• if the area is invaded by pathogens that have
  previously
• invaded the body, the specific immune response
  attacks the invaders

- pus a collection of dead neutrophils and cell
debris
- abcess a walled off sac of pus
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Inflammatory Response
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Antimicrobial Chemicals

• the body produces a number of chemicals that help
  kill
• Invading organisms

• Complement a group of 20 chemicals that
  circulate
• in the bloodstream

- Interferon a chemical that protects cells
from viral invasion

• pyrogens chemicals that reset the bodys
  thermostat
• causes fever

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Complement

• attaches to bacteria, fungal, or other foreign
  cells
• this process is called complement fixation

- it lyses the cells by damaging the cell
membranes
- it attracts phagocytes a process called
chemotaxis

• it makes foreign cells easier to phagocytize a
  process called
• opsonification

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Activation of Complement
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Interferon
- released by cells that have been invaded by a
virus
- it binds to the cell membrane of uninvaded cells
- it hinders the virus ability to invade the cell
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Pyrogens

• chemicals secreted by WBCs when they are exposed
• To invading cells

- they cause a fever by resetting the bodys
thermostat
- fever inhibits bacteria and enhances the
inflammatory response
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Specific Body Defenses The Immune System
- The immune response is the bodys response to
specific invaders
- it is called the bodys third line of defense
- it produces immunity (specific protection) to
specific invaders
- Immunology the study of immunity

• Immunity results in the production of proteins
  called
• antibodies that protect the body

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Immune Response Important Aspects

• it is antigen specific it recognizes a
  particular
• foreign substance

- It is systemic immunity protects the entire
body

• It has memory it recognizes and mounts a
  stronger
• attack on previously encountered pathogens this
  is
• known as the ananestic response

- Immunity has two parts
Humoral antibodies in the bloodstream Cell
mediated lymphocytes that attack and destroy
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Antigens
- Any substance or cell that is foreign to our
body
- they are large molecules that are normally not
in our body

• Proteins make the strongest antigens
• elicit the strongest immune response)

- Antigens can be nucleic acids, carbohydrates,
or lipids

• Small molecules usually are not antigenic
  however, they can
• Bind with our own proteins to produce larger
  molecules that
• Are antigenic. The small molecule is called a
  haptein.

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Cells of the Immune System Overview

• B Lymphocytes produce antibodies that produce
• humoral immunity

• T Lymphocytes various types that attack
  invading cells
• in different ways to produce the cell mediated
  immunity

- Macrophages help lymphocytes produce immunity
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Humoral Immune Response Antibody Mediated
- Antibodies are proteins that bind to and
inactivate antigens
- Antibodies are produced by B-Lymphocytes
- B-Lymphocytes are activated by binding to and
antigen

• The activated B-Lymphs divide rapidly to form a
  colony
• of many indentical cells called clones

• The clones then form either plasma cells (produce
  antibodies)
• Or memory cells (produce the ananestic response)

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Humoral Response
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Plasma Cells and Memory Cells

• Plasma cells produce large amounts of antibody
• antibody levels peak about 10 days after
  exposure,
• then he levels fall off

• Memory cells remember the antigen and can respond
  quickly
• To it again if needed

The secondary response is much quicker antibody
levels peak in 2 3 days
Antibody is produced at a much higher level and
remains high for weeks to months
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Humoral Response
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Active and Passive Humoral Immunity
Active Immunity antibodies produced by contact
of B Lymphs with and antigen. There are two
types of active Immunity
Natural immunity produced after exposure to the
pathogen
Passive immunity as a result of a vaccine
There are two types of vaccine killed and
attenuated (modified live)
The term vaccine applies only to viruses
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Passive immunity antibodies against an antigen
are given to a patient.
These antibodies have been manufactured by
another person and given to the patient
The patients own immune system does not make
these antibodies.
Passive natural immunity refers to antibodies
that are passed from a mother to her child
either through the Placenta or through the milk.
Passive artificial immunity refers to antibodies
that have been given to a patient from a donor.
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There are five classes of antibodies
IgG is the most abundant antibody in the blood
plasma It is the main antibody in primary and
secondary responses
IgA is the primary antibody found in the
secretions from mucous Membranes saliva, tears,
milk, intestinal lining. It protects mucous
membranes from pathogens.
IgE is secreted by skin and mucous membranes.
It is the primary mediator of allergic reactions.
IgM is found in plasma both free and attached to
B lymphs. It serves as an antigen receptor.
IgD is found in the plasma attached to B
lymphs. It serves a role in the activation of B
lymphs.
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Cell Mediated Immunity
T lymphs are activated by antigen that is
presented to them in the cell membranes of
macrophages. They cannot bind to free antigen.
Without antigen presentation by the macrophage
the T lymphs cannot respond to an antigen.
Activated T lymphs form several types of clones

1. Cytotoxic (killer ) T cells kill virus
infected cells as well as foreign graft cells
2. Helper T cells they serve as directors of
the immune response They stimulate B lymphs to
more rapidly produce clones They stimulate
antibody production They release lymphokines
chemicals that stimulate both the humoral and
cell mediated immune response
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3. Suppressor T cells they lessen the immune
response and help bring it to an end.
4. Delayed hypersensitivity T cells they play a
role in delayed allergies and chronic
inflammation
5. Memory cells provide antigenic memory that
allows the body to respond more quickly to
subsequent exposure
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Organ Transplants and Rejection
Transplantation of organs or tissue grafts from
living or recently deceased donors is a viable
treatment option for many patients, including
Kidney failure
Heart failure
Burn patients
Immune rejection presents a major problem for
these patients
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There are four varieties of tissue grafts
Autografts tissue transplanted from one site to
another site on the same person.
Isografts grafts donated by genetically
identical individuals i.e. only identical twins
Allografts tissues transplanted from non
genetically identical individuals of the same
species.
Xenografts tissue grafted from a donor of a
different species
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Autografts and isografts present no risk of
rejection the tissues of donor and recipient
are identical
Xenografts are only temporarily successful Due
to vast differences in tissue proteins
Allografts are often successful. Success is the
result of similar tissue antigens.
Blood and tissue from donor and recipient must be
tested to determine compatibility.
Patients are treated with immunosuppressive drugs
to prevent rejection.
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Immune Deficiencies
A defect in the immune system inhibits the
bodys ability to defend itself
Severe Combined Immunodeficiency Syndrones
A group of genetic defects that interfere with
both B cell and T cell function. Patients have no
defense against disease causing organisms Tx
include- bone marrow transplants, protective
barriers
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Acquired Immune Deficiency Syndrone (AIDS)
Destroys the immune system by interfering
with helper T cells.
AIDS is caused by the human immunodeficiency
Virus (HIV
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Autoimmune Diseases
The body produces antibodies and sensitized T
cells that destroy its own tissue. The specific
disease produced depends on the target tissue
involved. Examples include
Multiple sclerosis white matter in CNS is
destroyed
Myasthenia gravis nerve and muscle communication
Graves disease thyroid gland over active
Juvenile diabetes pancreatic beta cells
Systemic lupus erythematosus can affect the
kidneys, heart, Lungs, skin
Rheumatoid athritis - joints
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Hypersensitivities
Also called allergies. The body is harmed as the
immune System fights a perceived threat that
is otherwise harmless
The term allergen is used to identify this type
of antigen.
There are two types of allergic reactions
immediate and delayed.
Immediate hypersensitivity begin within seconds
of contact. Lasts about a half an hour. This
reaction is caused by histamine. Can be local or
systemic Anaphylactic shock an ovewhelming,
systemic, life threatening reaction
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Delayed Hypersensitivity
An antibody mediated reaction that develops more
slowly one to three days
Examples include
Contact dermatitis Poison ivy