Transcript Biol 155 Human Physiology - University of British Columbia

Lymphatic System and
Immunity:
Lymphatic System
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Lymph
Lymphatic vessels
Lymphatic tissue
Lymphatic nodules
Lymph nodes
Tonsils
Spleen
Thymus
Lymphatic Vessels
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Carry lymph away from tissues
Lymphatic capillaries
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More permeable than blood capillaries
Epithelium functions as series of one-way valves
Functions of the Lymphatic
System
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Fluid balance
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Fat absorption
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Excess interstitial fluid enters lymphatic
capillaries and becomes lymph
Absorption of fat and other substances from
digestive tract
Defense
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Microorganisms and other foreign substances are
filtered from lymph by lymph nodes and from
blood by spleen
Lymphatic Vessels
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Carry lymph away from tissues
Lymphatic capillaries
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More permeable than blood capillaries
Epithelium functions as series of one-way valves
Lymphatic Vessels
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Lymphatic capillaries join to form
Lymphatic vessels
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Have valves that ensure one-way flow
Lymph nodes: Distributed along vessels and
filter lymph
Lymphatic trunks: Jugular, subclavian,
bronchomediastinal, intestinal, lumbar
Lymphatic ducts: Right and thoracic which
connect to large veins
Lymph Drainage Into Veins
Lymphatic Tissue and Nodules
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Lymphatic tissue
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Consists mainly of
lymphocytes
Encapsulated or not
Lymphatic nodules
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Numerous in loose
connective tissue of
digestive (Peyer’s
patches), respiratory,
urinary, reproductive
systems
Tonsils
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Large groups of lymphatic
nodules in nasopharynx
and oral cavity
Provide protection against
bacteria and other harmful
material
Groups
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Palatine
Pharyngeal
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Lingual
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Lymph Nodes
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Organized in cortex and medulla
Substances removed by phagocytosis or stimulate
lymphocytes or both
Only structures to filter lymph
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Afferent and efferent vessels
Spleen
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Located in left superior side of abdomen
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Blood flows through at 3 different rates
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Can be ruptured in traumatic abdominal injuries
resulting in bleeding, shock, death
Fast (most), slow, intermediate
Functions
Destroys defective RBCs
 Detects and responds to foreign substances
 Limited reservoir for blood
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Spleen
Thymus
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Located in superior mediastinum
Divisions: Cortex and medulla
Site of maturation of T cells
Immunity
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Ability to resist damage from foreign substances as
microorganisms and harmful chemicals
Categories
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Innate or nonspecific resistance
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Mechanical mechanisms: Prevent entry or remove microbes
Chemical mediators: Promote phagocytosis and inflammation
Cells: Involved in phagocytosis and production of chemicals
Adaptive or specific immunity
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Specificity: Ability to recognize a particular substance
Memory: Ability to remember previous encounters with a particular
substance and respond rapidly
Innate immunity
Inflammatory Response
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Tissue injury regardless of type can cause inflammation
Response initiated by chemical mediators that produce
vasodilation, chemotactic attraction, increased vascular
permeability
Types
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Local: Symptoms are redness, heat, swelling, pain, loss of
function
Systemic: Symptoms are increase in neutrophil numbers,
fever and shock
Inflammatory Response
Normal Microcirculation Flow
Exudate Formation
Leukocyte Margination and Migration
Diapedesis
Chemotaxis
Innate Immunity: Cells
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White blood cells
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Most important cellular
components of immune
system
Methods
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Chemotaxis
Phagocytosis
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Phagocytic and first
cells to enter infected
tissue
Promote inflammation
Eosinophils
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Monocytes that leave
blood, enter tissues
Large phagocytic cells
Basophils and mast cells
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Neutrophils
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Macrophages
Reduce inflammation
Natural killer cells
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Lyse tumor and virusinfected cells
Antigenic Determinants
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Antigenic determinants
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Specific regions of a given
antigen recognized by a
lymphocyte
Antigenic receptors
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Surface of lymphocyte
that combines with
antigenic determinant
C3a stimulates mast cells
and basophils, which
then secrete
inflammatory mediators
Adaptive Immunity
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Involves the ability to recognize, respond to, and
remember a particular substance
Stimulants
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Antigens: Large molecules
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Foreign: Not produced by body, introduced from outside
Self-antigens: Produced by body
Haptens: Small molecules and capable of combining
Types
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Humoral or Antibody-mediated: B cells
Cell-mediated: T cells
Origin and Development
of Lymphocytes
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B and T cells
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Originate in red bone
marrow
Move to lymphatic
tissue from processing
sites and continually
circulate
Clones are small groups
of identical lymphocytes
Origin and Development
of Lymphocytes
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Positive selection
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Negative selection
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Eliminates lymphocytes that react against self-antigens
Primary lymphatic organs (red bone marrow, thymus)
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Ensures survival of lymphocytes that react against
antigens
Where lymphocytes mature into functional cells
Secondary lymphatic organs
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Where lymphocytes produce an immune response
Major Histocompatability
Complex (MHC)
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Most lymphocyte activation involves
glycoproteins of cell surfaces called MHC
molecules
Class I molecules display antigens on surface of
nucleated cells, resulting in destruction of cells
 Class II molecules display antigens on surface of
antigen-presenting cells, resulting in activation of
immune cells
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Antigen Processing
MHC class I
Phagocytosis
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Phagocytosis also involves membrane
invagination.
This process does not involve clathrin.
Pseudopods extend around a particle,
forming a phagosome.
Phagosome will fuse with a lysosome,
containing digestive enzymes.
There are smaller transport mechanisms
in the wall of the secondary lysosome.
Costimulation
Proliferation of Helper T Cells
Proliferation of B Cells
Lymphocyte Inhibition
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Tolerance: To prevent the immune system from
responding to self-antigens
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Provoked by
Deletion of self-reactive lymphocytes
 Preventing activation of lymphocytes
 Activation of suppressor T cells
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Antibody-Mediated Immunity
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Antibodies or
Immunoglobulins (Ig)
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Classes: IgG, IgM, IgA,
IgE, IgD
Structure
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Variable region: Part that
combines with anitgenic
determinant of antigen
Constant region:
Responsible for activities
Actions of Antibodies
Antibody Production
Cell-Mediated Immunity
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Antigen activates effector T cells and produces memory T cells
Cytotoxic T cells lyse virus-infected cells, tumor cells, and tissue
transplants
Cytotoxic T cells produce cytokines, which promote phagocytosis
and inflammation
Interactions and Responses of
Innate and Adaptive Immunity
Ways to Acquire
Adaptive Immunity
Effects of Aging
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Little effect on lymphatic system
Decreased ability of helper T cells to
proliferate in response to antigens
Decreased primary and secondary antibody
responses
Decreased ability of cell-mediated immunity
to resist intracellular pathogens
Immune System Problems
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Hypersensitivity reactions
Autoimmune disease
Severe combined immunodeficiency disease
(SCID)
Transplantation
Acute rejection
 Chronic rejection
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