Download Chapter 14 – The Lymphatic System and Immunity

The Lymphatic System and Immunity
The other circulatory system
Summary
 Lymphatic system
 Fluid
 Vessels
 Nodes and Nodules
 Organs
 Immune system
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Nonspecific
Specific
Cells
Mechanisms
Lymphatic System
 Function – responsible for returning tissue fluid to the blood
and for protecting the body against foreign material.
 Lymph is a specialized fluid which is formed in the tissue
spaces = interstitial fluid. Contains excess fluid and protein
molecules that cannot enter or return through the capillary
walls.
Lymphatic System
 Lymphatic vessels
 Lymph capillaries – blind ended vessels that are very
permeable; collect tissue fluids and proteins in the tissues.
Lymphatic System
 Vessels cont’d
 Lymph venules then veins collect fluid from the capillaries.
 Ducts – large vessels that drain the lymph into the blood in
veins (subclavian) in the neck area.
 Right lymphatic duct
 Thoracic duct
Lymphatic System
 Vessels
 Cisterna chyli – enlarged pouch-like structure formed by the
union of the lower body lymphatic vessels. Lower portion of
the thoracic duct in the abdomen; serves as a storage area for
lymph that is moving toward its point of entry into the venous
system.
Lymphatic System
 Fluid is moving under low pressure and against gravity –
How?
 Smooth muscle in the walls of the larger vessels contracts and
moves fluid upward.
 Skeletal muscle pump
 Pressures in thoracic cavity
Lymphatic System
 Lymph Nodes
 Clusters of small encapsulated masses of lymphatic tissue
located at strategic spots in the lymph system. They may be the
size of a pin head or a lima bean.
 Lymph enters the node through afferent vessels (usually more
than one) and leaves through a single efferent vessel.
Lymphatic System
 Lymph Nodes
 Serve to filter and trap bacteria, cancer cells and other foreign
material picked up by the lymphatic vessels. Fixed macrophages
in the nodes phagocytize (eat) these particles.
 Fixed plasma cells produce antibodies in response to foreign
material and these antibodies then circulate in the blood stream.
 **Also produce lymphocytes and monocytes.
Lymphatic System
 Lymph Nodes
 Significant groups: cervical, axillary and inguinal.
 Clinical significance:
Lymphatic System
 Lymph Nodules
 Smaller masses of lymphatic tissue (not encapsulated) found just
beneath the epithelium of all mucous membranes.
 Mucous membranes are located at openings to the
environment – respiratory, digestive, urinary and
reproductive systems. Why is this a good spot for lymph
tissue?
Lymphatic System
 Special Lymph Nodules
 Peyer’s patches located in the small intestine.
 Tonsils – located in the pharynx form a protective ring under
the mucous membranes in the mouth and back of throat.
 Palatine –
 Pharyngeal –
 Lingual –
Lymphatic System
 Organs
 Thymus – located inferiorly to the thyroid gland in the
mediastinum. Produces T-lymphocytes (T-cells) and secretes
thymosin and other hormones that stimulate their development.
 The thymus is critical to immunity in the fetus and infant.
 The thymus shrinks with age but is still active.
Lymphatic System
 Spleen
 Largest lymphoid organ in the body located in the upper left
quadrant of the abdomen, lateral to the stomach, just below the
diaphragm.
 Functions:
Lymphatic System
 Spleen
 Functions:
 Fixed macrophages, reticuloendothelial cells, phagocytize pathogens in
the blood. Also phagocytize and destroy old RBCs producing bilirubin.
 Stores about 1 pint of blood – hemorrhage
 Splenectomy?
 Liver and red bone marrow will compensate to remove old RBC’s and
lymph nodes and nodules will produce lymphocytes and monocytes, etc.
Immune System
 Immunity – the body’s ability to destroy pathogens or other
foreign material and prevent further cases of certain
infectious diseases.
 Types of Immunity:
Immunity
 Non-specific (innate) immunity - maintained by mechanisms
that attack any abnormal substance that threatens the body;
general protection.
 Barriers: Skin, mucous membranes (and mucus), cilia.
 Lysozymes in tears and saliva.
 SQ and areolar connective tissue WBC phagocytize bacteria.
Immune System
 Specific immunity
 Includes protective mechanisms that confer very specific
protection against certain types of invading materials.
 Involves “memory” – when the body is attacked the first time a
disease develops; the next time no disease signs/symptoms
develop; i.e. the body is immune.
Immune System
 Specific Immunity - Inherited
 Genetic, inborn immunity is the result of our genetic make-up,
i.e. we do not get distemper and dogs don’t get measles (species
immunity).
 This type does not involve antibodies and the efficiency does
not increase with subsequent exposures.
Immune System
 Specific Immunity - Acquired
 Natural – exposure to the causative agent is not deliberate.
 Active –
 Passive –
Immune System
 Specific Immunity – Acquired
 Artificial – exposure to the causative agent is deliberate.
 Active - injection of the agent (vaccine) results in production of your own
antibodies and memory cells.
 Passive – injection of protective material (antibodies) that was developed
by another individual’s immune system (gamma globulins or immune
globulins).
Immune System - Cells
 Phagocytes – neutrophils, monocytes and macrophages,
derived from bone marrow, carry out ingestion and digestion
of foreign cells or particles.
 Monocytes develop into macrophages.
 Macrophages – some wander and some are fixed; example
Kupffer’s cells in the spaces between liver cells.
Immune System - Cells
 Lymphocytes – most numerous cells of the immune system;
responsible for antibody production
 T-cells – produced in the bone marrow and thymus of the
embryo. They mature in the thymus and migrate to the spleen,
lymph nodes and nodules.
Immune System - Cells
 Lymphocytes
 B-cells – produced in the bone marrow
 When activated by an antigen, they become plasma cells that produce
antibodies.
 They also can become memory cells that remain in reserve until a
stimulus by the same antigen is repeated and then produce antibodies.
Immune System Cells
 Lymphocytes
 Natural Killer Cells (Killer T-cells) – smaller in number but can
attack many types of pathogens and tumor cells. Formed from
activated T-cells. Mechanism : disrupt cell membranes of
foreign cells.
Immune System - Cells
 Review Definitions:
 Antigen – chemical markers that identify cells. Each cells has
its own set of markers.
 Antibodies (immune or gamma globulins)
 Proteins produced by plasma cells in response to foreign antigens; each
one is specific for a certain antigen.
 Mechanism: When bound to an antigen they cause agglutination
(clumping) of the material.
 Also the mechanism for allergic responses.
Mechanisms of Immunity
 Recognition of an antigen as foreign – accomplished by
macrophages and helper T-cells.
 Foreign antigen is phagocytized by a macrophage.
 Macrophage presents antigen material on its cell
membrane.
 Helper T-cell is exposed to this part of the macrophage
membrane and becomes sensitized.
Mechanisms of Immunity
 Once an antigen has been recognized, the activated helper T
cells initiate one or both immune mechanisms.
 Cell Mediated Immunity
 Humoral Immunity
Mechanisms of Immunity
 Cell- mediated Immunity – no antibody produced
 T-cells activated by foreign material form memory T-cells and
killer (cytotoxic) T-cells.
 Memory cells will remember the specific antigen and become
active if it enters body again.
 Killer T-cells chemically destroy foreign antigens (disrupt cell
membranes).
Mechanisms of Immunity
 Cell-mediated immunity
 T-cells cont’d
 Killer T-cells also produce cytokines – chemicals that attract
macrophages to an area to promote phagocytosis.
 Suppressor T-cells stop the immune response once the
antigen has been destroyed.
Mechanisms of Immunity
 Humoral Immunity – involves production of antibodies.
 Recognition of foreign antigen by macrophages and activation of
helper T-cells.
 Sensitized helper T-cell presents antigen to B-cells
 B-cells activate the memory B cells and plasma cells. The
plasma cells then produce antibodies.
Mechanisms of Immunity
 Humoral Immunity
 Antibodies bind to antigens forming an antigen-antibody
complex.
 Complex is labeled for phagocytosis by macrophages =
opsonization.
 Complement fixation – complement binds to complex and is
destroyed by lysis.