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Chapter 13
Lecture Outline
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13.1 Lymphatic System
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A. Functions of the Lymphatic System
1.
2.
3.
Fluid balance – takes up excess tissue fluid
and returns it to the blood stream
Fat absorption – from the digestive tract
into lacteals and transports them to the
blood stream
Defense – works with the immune system
to protect against disease
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B. Lymphatic vessels
1.
2.
Form a one-way system
Begins with lymphatic capillaries
a. Tiny, closed-ended vessels
b. Take up excess tissue fluid (lymph)
3.
Vessels merge and then enter one of two ducts
that enter the right and left subclavian veins
a. Thoracic duct – drains the left side of the head,
left chest, left arm, and the lower body
b. Right lymphatic duct – drains the right side of
the head, right chest, and right arm
4.
Vessels have valves and movement of lymph
depends on skeletal muscle contraction
5.
Edema is localized swelling caused by the
accumulation of lymph
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The lymphatic system
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13.2 Organs, tissues, and cells of
the immune system
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A. Introduction
1.
2.
The immune system is a network of
lymphatic organs, tissues, and cells, as
well as products of the cells
Immunity – the ability to react to antigens
to remain free of disease
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B. Primary lymphatic organs
1.
Lymphocytes originate and/or mature in these
organs
2.
Red Bone Marrow
a. Site of stem cells that produce blood cells
b. In an adult, red bone marrow is found in the
sternum, vertebrae, ribs, skull, part of the
pelvic girdle, and proximal heads of the
humerus and femur
c. Lymphocytes differentiate into B and T
lymphocytes and natural killer (NK) cells
1) B lymphocytes mature in the red bone
marrow
2) T lymphocytes mature in the thymus
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Primary lymphatic organs, cont
3.
Thymus Gland
a. In the thoracic cavity
b. Largest in children and shrinks as a
person ages
c. Lobules are filled with lymphocytes
d. Produces thymic hormones called
thymosins
1) Aids in maturation of T lymphocytes
2) May have other functions in immunity
e. Functions is critical to immunity
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C. Secondary lymphatic organs
1.
Places where lymphocytes encounter and bind
with antigens
2.
Spleen
a. Largest lymphatic organ
b. Consists of two types of tissue:
1) White pulp – has a concentration of
lymphocytes
2) Red pulp – surrounds venous sinuses and is
involved in filtering blood
c. Blood entering the spleen is filtered through
venous sinuses
1) Lymphocytes and macrophages react to
pathogens
2) Macrophages engulf debris and remove old
red blood cells
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Secondary lymphatic organs, cont
3. Lymph nodes
a. Small structures occurring along lymphatic
vessels
b. Forms a capsule of connective tissue
c. Node is divided into compartments
1) Contains nodules packed with B lymphocytes
and macrophages
2) Sinus that contains T lymphocytes
d. Lymph passing through the sinus is filtered by
macrophages
e. T lymphocytes fight infection and attack cancer
cells
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Secondary lymphatic organs, cont
4.
Lymphatic nodules
a. Concentrations of lymphatic tissue not
surrounded by a capsule
b. Tonsils in the pharynx and oral cavity
c. Peyer patches in the wall of the small
intestine
d. Appendix – attached to the large
intestine
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13.3 Nonspecific and specific
defenses
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A. Nonspecific Defenses
1.
Barriers to entry
a. Physical
1) Intact skin
2) Mucous membranes and cilia
b. Chemical
1) Sebaceous gland secretions
2) Lysozyme in perspiration, saliva, and
tears
3) Urine
4) pH of the stomach
5) Normal flora
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2. Inflammatory reaction
a. Four signs due to capillary changes in
damaged tissue
1) Redness
2) Heat
3) Swelling
4) Pain
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b. Steps of inflammatory reaction
1) Chemical mediators, such as histamine, cause
capillaries to dilate and become more permeable
a) Excess blood causes redness and increased
temperature
2) Increased permeability causes fluids and proteins to
escape the capillaries and cause swelling and pain
3) Edema and clot formation “wall off” the area
4) Migration of phagocytes (monocytes and
neutrophils)
5) Monocytes become macrophages that devour
pathogens and debris
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Steps of inflammatory reaction
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Nonspecific Defenses, cont
3. Natural killer cells
a. Kill virus-infected cells and tumor cells
b. Large, granular lymphocytes
c. No specificity and no memory
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4. Protective proteins
a.
Complement
1) Composed of blood plasma proteins
2) Activated when pathogens enter the body
3) Amplify the inflammatory response
4) Bind to the surface of pathogens, ensuring that
they will be phagocytized
5) Form a membrane attack complex that punches
holes in the walls and membranes of bacteria
b.
Interferon
1) Produced by virus-infected cells
2) Produce substances that interfere with viral
replication
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Three Lines of Defense
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B. Specific Defenses
1.
Introduction
a. Respond to antigens and distinguishes
from “self-antigens”
b. Lymphocytes have antigen receptors
1) B lymphocytes
a) Mature in the bone marrow
b) Give rise to plasma cells that
produce antibodies
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Introduction to specific defenses, cont
2) T lymphocytes
a) Mature in the thymus gland
b) Directly attack cells that have nonself
proteins
c) Regulate the immune response by
producing cytokines
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2. B cells and antibody-mediated immunity
a.
b.
Also called humoral immunity
Clonal Selection
1)
When B cells encounter an antigen they are activated to
divide many times
2)
Clones
a) Most mature to form plasma cells (with the same
antigen receptor) that produce antibodies
b) Some become memory cells
1) Make long-term immunity possible
2) A second exposure to the same antigen produces a
stronger, faster immune response
3)
Plasma cells undergo apoptosis when an infection has
passed
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Clonal selection theory and B cells
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c. Structure of antibodies
1)
Basic unit is a Y-shaped protein molecule
with two arms (4 protein strands)
2) Chains have constant regions at the trunk
of the Y that determines the antibody class
a) Monomers – single Y-shaped molecules
b) Dimers – paired Y-shaped molecules
c) Pentamers – clusters of 5 Y-shaped
molecules linked together
3) Variable region forms an antigen binding
site with a specific shape to match an
antigen
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Structure of a single antibody
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d. Function of antibodies
1)
2)
3)
Neutralization – covering toxins on surface
membranes
Forming immune complexes to enhance
phagocytosis
Activation of complement for cell lysis or
phagocytosis
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Functional classes of antibodies
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3. T cells and cell-mediated immunity
a.
Antigen must be presented to T cells by an
antigen-presenting cell (macrophage or B
cell)
b. Major histocompatability (MHC) proteins
1) Called HLA (human leukocyte antigens)
2) Are self proteins
c. T cell compares the antigen and the self
protein
1) Activated T cell and all daughter cells
can recognize “foreign” from “self”
2) Will destroy cells carrying foreign
antigens
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Clonal selection theory and T cells
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d. Types of T cells
1)
Cytotoxic T cells (CD8 leukocytes)
a) Destruction of virus-infected or cancer
cells
b) Have storage vacuoles containing
Perforin molecules
c) Perforin punches holes in the plasma
membrane causing cell lysis
d) Responsible for cell-mediated immunity
2) Helper T cells (CD4 leukocytes) regulate
immunity by secreting cytokines that
stimulate various immune cells to perform
their functions
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Types of T cells, cont
3)
Memory T cells – provide a faster response
to an antigen that had previously been
present in the body
4) Cytokines in Cancer Chemotherapy
a) Used as immunotherapeutic drugs to
enhance the ability of T cells to fight
cancer
b) Interferon and interleukins are also used
as immunotherapeutic drugs
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Cell-mediated immunity
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13.4 Creating an immune response
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A. Active immunity
1.
Natural active immunity
a. Actual exposure to the antigen
b. Primary response occurs
c. Generally get sick
d. Make antibodies and memory cells
2. Artificial active immunity
a. Involves the use of vaccines to cause a
primary response
b. Generally do not get sick
c. A second exposure produces a faster and
larger secondary response
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Vaccine responses
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B. Passive immunity
1.
Natural passive immunity
a. Occurs when a mother passes antibodies
to a child through the placenta or
mother’s milk
b. Temporary – no memory cells
2. Artificial passive immunity
a. Occurs when an individual is given
prepared antibodies (immunoglobulins)
b. Is temporary – no memory cells
c. Can be used in the event of an
unexpected exposure to an infectious
disease
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C. Monoclonal antibodies
1.
2.
3.
4.
5.
Every plasma cell derived from the same B
cell
Secretes antibodies against one antigen
Can be produced in vitro using myeloma
cells
Are being used for quick and certain
diagnosis of various conditions
Used to carry radioactive isotopes or toxic
drugs to tumors
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Production of monoclonal antibodies
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D. Hypersensitivity reactions
1.
Allergies
a. Response to substances that are usually
harmless to the body (allergens)
b. IgE-Mediated Allergic Response
1) Immediate allergic response
2) Caused by IgE antibodies
3) When an allergen attaches to the IgE
antibodies, histamine is released
4) Anaphylactic shock occurs when the
allergen has entered the blood stream
causing vasodilation and extreme drop
in blood pressure
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Allergies, cont
c.
T-Cell Mediated Allergic Response
1) Delayed allergic response
2) Initiated by memory T-cells at the site
of allergen contact
3) Regulated by cytokines
4) Examples – contact dermatitis, TB test
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2. Tissue rejection
a.
Transplanted tissue is recognized as not
“self”
b. Cytotoxic T cells cause disintegration of
the transplanted tissue
c. Can be controlled by:
1) Selecting organs that have the same
type of HLA antigens as those of the
recipient
2) Administering immunosuppressive
drugs such as cyclosporine or
tacrolimus
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3. Autoimmune diseases
a. Cytotoxic T cells or antibodies attack the body’s own
cells
b. Cause is unknown; some are hereditary
c. Examples:
1) Myasthenia gravis
2) Multiple sclerosis
3) Systemic lupus erythematosus
4) Rheumatoid arthritis
5) Type 1 diabetes
6) Crohn’s disease
7) Ulcerative colitis
d. No cures, but can be managed with medications
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E. Immune deficiency
1.
2.
3.
4.
The immune system is unable to protect
the body from disease
Can be acquired or genetic
Without treatment, common infections
can be fatal
Examples – AIDS and SCID
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13.5 Effects of Aging
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Effects of Aging
A.
B.
C.
D.
E.
F.
Aging people become more susceptible to
infections and disorders
Thymus gland degenerates and number of
T cells decreases
B cells sometimes do not form clones
Antibodies do not function as well
Incidence of autoimmune diseases
increases
Response to vaccines is decreased
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13.6 Homeostasis
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Homeostasis
A.
The lymphatic system helps the following:
1. The digestive system by absorbing fat
2. The cardiovascular system by absorbing lymph
3. The immune system in protection against
infectious diseases
B.
Nonspecific immune responses are dependent on:
1. The skin
2. Mucous membranes of the respiratory tract, the
digestive tract, the reproductive and urinary
systems
C.
Specific defenses are dependent on blood cells
D.
There is a strong connection between the
immune, nervous, and endocrine systems
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Human systems work together
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