Post on 25-Dec-2015
LYMPHATIC SYSTEM AND BODY DEFENSES
LYMPHATIC AND IMMUNE SYSTEM (COPY)
1. Describe the roles of the immune and lymphatic systems. 2. Explain why antibiotics are effective against bacteria but
not against viruses 3. Outline the role of skin and mucous membranes in defense
against pathogens. 4. Outline how phagocytic leucocytes ingest pathogens in the
blood and in body tissues. 5. Distinguish between antigens and antibodies. 6. Explain antibody production. 7. Describe the process of blood clotting. 8. Outline the principle of challenge and response, clonal
selection and memory cells as the basis of immunity. 9. Describe the production of monoclonal antibodies and their
use in diagnosis and in treatment. 10. Explain the principle of vaccination. 11. List the functions of the spleen and thymus.
LYMPHATIC SYSTEM
Defense against disease Consists of two semi-independent parts:
Network of lymphatic vessels Various lymphoid tissues and organs throughout
body Lymphatic vessels transport fluids that have
escaped from the blood vascular system back to the blood.
Lymphoid organs house phagocytic cells and lymphocytes
LYMPHATIC VESSELS
Fluid is forced out of the blood in the capillary beds, and most of it is reabsorbed at the venous ends.
About 3 L per day are left behind this becomes part of the interstitial fluid, and is now called lymph.
This fluid must return to the bloodstream in order to have enough volume for the cardiovascular system to function
If this does not happen, fluid starts to build up in the tissues, producing edema (swelling)
LYMPHATIC VESSELS
One way system vessels only flow towards the heart
Low-pressure and pumpless system Lymph capillaries = microscopic, blind
ended vessels that spread out between tissues cells and blood capillaries in the loose connective tissues of the body.
Little valves at the end open when fluid pressure is higher in the interstitial space, but close up when the pressure is higher inside the lymphatic vessels prevents leaks
LYMPHATIC VESSELS
Large particles like proteins, cell debris, bacteria, and viruses can’t enter blood capillaries, but they can enter lymphatic capillaries, especially in inflamed areas
Now the bacteria and viruses can travel throughout the body how do we solve that problem?
Lymph takes “detours” through lymph nodes gets cleaned of debris and “examined” by cells in the immune system
LYMPHATIC VESSELS
Lymph moves from lymph capillaries to successively larger lymphatic vessels (lymphatic collecting vessels), similar to how blood moves from capillaries to venules to veins.
Lymph returns to venous system through one of two large ducts: Right lymphatic duct – drains lymph from right arm and
right side of head and thorax Thoracic duct – receives lymph from the rest of the body
Both ducts empty into subclavian veins Lymphatic vessels are thin walled and the larger ones
have valves to prevent backflow, like veins. Also helped by skeletal muscles “milking” the lymph
along and pressure change in the thorax during breathing.
LYMPH NODES Help protect the body by removing foreign material
such as bacteria and tumor cells from the lymphatic stream as well as producing lymphocytes.
Lymph nodes = filters Large clusters can be found in the inguinal (hips),
axillary (armpits), and cervical (neck) regions of body.
Contain macrophages, which engulf and destroy bacteria, viruses, and other foreign substances found in lymph
Also contain lymphocytes, a type of WBC Active infection usually results in swollen glands due
to the trapping function of the nodes.
LYMPH NODES Usually kidney-shaped, less than 1 inch long, and
“buried” in connective tissue that surrounds them. Each node is surrounded by a fibrous capsule Trabeculae = strands that extend into the capsule to
divide them into compartments Cortex = outer part of the node, contains collections
of lymphocytes called follicles Germinal centers = dark centers of follicles that
enlarge when B lymphocytes generate plasma cells Medulla = center of lymph node, contains
phagocytic macrophages Lymph enters through afferent lymphatic vessels,
moves through sinuses, and exits through efferent lymphatic vessels.
LYMPH NODES
SPLEEN
Blood rich organ that filters blood Located on the left side of abdominal cavity, curls
around stomach Doesn’t filter lymph, it filters blood and cleans out
bacteria, viruses, and other debris Destroys worn out RBCs and returns their
breakdown products to the liver Stores platelets and acts as a blood reservoir (like
the liver) During hemorrhage, the spleen will contract and
empty its stored blood back into circulation to help keep levels normal
Forms all blood cells in a fetus, but only lymphocytes are made in adults
THYMUS
Lymphatic mass found low in throat overlying the heart
Produces hormones (thymosin and others) that function in the programming of certain lymphocytes so that they can protect the body
Functions at peak levels only during youth
TONSILS
Small masses of lymphatic tissue that ring the pharynx (throat)
Trap and remove any bacteria or other foreign pathogens entering the throat
Sometimes they work too well get congested with bacteria and become red, swollen, and sore = tonsillitis
PEYER’S PATCHES
Resemble tonsils, but found in wall of small intestine
Macrophages in ideal position to capture and destroy bacteria lots of bacteria in intestine
Help stop bacteria from penetrating intestinal wall
Peyer’s patches and tonsils are known as mucosa-associated lymphatic tissue (MALT)
MALT protects upper respiratory and digestive tracts never-ending attacks of foreign matter
LYMPHOID ORGANS
WARM UP - IDENTIFY THE LYMPHATIC ORGAN AND FUNCTION(S)
Organ Function(s) Location
1. Explain the function of the Lymphatic System2. Explain the relationship between the lymphatic system and the
circulatory system.3. Explain the relationship between the Lymphatic System and the
Immune System.
BODY DEFENSES
Two main systems: Nonspecific – responds immediately to protect
body from all foreign substances, reduces workload of specific defense system Intact skin and mucous membranes Inflammatory response
Specific – aka immune system, attacks particular foreign substances Lymphatic organs Blood vessels White blood cells
SURFACE MEMBRANE BARRIERS
First line of defense = skin and mucous membranes
Act as physical barriers Acid pH of skin inhibits bacterial growth Stomach mucosa makes hydrochloric acid
and protein-digesting enzymes, which helps kill pathogens
Saliva and tears contain lysozyme, an enzyme that destroys bacteria
Sticky mucus traps microorganisms in digestive and respiratory pathways
CELLS AND CHEMICALS
Second line of defense Phagocytes – engulfs a foreign particle and digests
it Natural killer (NK) cells – lyse and kill cancer cells
and virus-infected cells can react against any target. They attack the cell’s membrane and release chemicals that cause it to disintegrate
Fever – abnormally high body temperature, pyrogens are chemicals secreted by WBCs that raise body temperature, fevers can be very dangerous if they get too hot or last too long
Inflammatory response – triggered when body tissues are injured 4 cardinal signs = redness, heat, swelling, and pain.
INFLAMMATORY RESPONSE
Injured cells release histamine and kinins Cause blood vessels to dilate and capillaries
to become “leaky” increased blood flow Activate pain receptors Attract phagocytes and WBCs to area
chemotaxis = cells following chemical gradient
Swelling (edema) is the result causes more pain
The inflammatory response prevents the spread of damaging agents, disposes of cell debris and pathogens, and sets the stage for repair
IMMUNE SYSTEM
Third line of defense Immune response – immune system’s
response to a threat; increases inflammatory response and provides protection against specific antigens
Recognizes foreign molecules (antigens) and actively works to destroy them
Can recognize previously encountered antigens and trigger immune responses
Immunology – study of immunity Some diseases that result from a
malfunctioning immune system: cancer, rheumatoid arthritis, AIDS
THREE IMPORTANT ASPECTS OF IMMUNE RESPONSE:
1. Antigen specific – recognizes and acts against particular pathogens or foreign substances
2. Systemic – Immunity is not restricted to the initial infection site
3. “Memory” – recognizes and mounts stronger attacks on previously encountered pathogens
TWO KINDS OF IMMUNITY
1. Antibody-mediated immunity (humoral immunity) = provided by antibodies present in body’s fluids.
2. Cell-mediated immunity = Lymphocytes themselves defend the body, either by directly lysing foreign cells or indirectly releasing chemicals that enhance inflammatory response
ANTIGENS
Any substance capable of exciting our immune system and provoking an immune response.
Tend to be large Not normally present in our bodies Foreign intruders “non-self” Our own cells have self-antigens, which are
recognized by our body, but would trigger an immune response in someone else (organ transplant rejections)
CELLS OF THE IMMUNE SYSTEM
Lymphocytes B lymphocytes (B cells) – produce antibodies and
oversee antibody-mediated immunity T lymphocytes (T cells) – do not produce antibodies
and oversee cell-mediated immunity Lymphocytes must be able to recognize body’s
own cells so they won’t attack them Lymphocytes get “trained” to recognize one
distinct antigen to attack = immunocompetent Since lymphocytes become immunocompetent
before being exposed to antigens, we know it is our genes, not antigens, that determine what foreign substances we will be able to resist.
CELLS OF THE IMMUNE SYSTEM
Macrophages – “big eaters” Engulf foreign particles and present
fragments of these antigens on their own surfaces
Allow these particles to be recognized by immunocompetent T cells – antigen presenters
Macrophages secrete monokines, which activate T cells
Active T cells release chemicals that turn macrophages into killer macrophages
USE YOUR NOTES TO ANSWER THE FOLLOWING QUESTIONS
1. Outline the role of skin and mucous membranes in defense against pathogens.
2. Distinguish between antigens and antibodies.
3. Explain the principle of vaccination.4. List the functions of the spleen and thymus.5. Explain how the Lymphatic and Immune
system work together.
ANTIBODY-MEDIATED RESPONSE
Primary humoral response = Immature B cell binds to antigen gets activated and undergoes clonal selection (mass produces an army of cells like itself)
Afterwards, most clones become plasma Some become long-lived memory cells and
can respond to the antigen when they encounter it later = secondary response
TWO KINDS OF HUMORAL IMMUNITY
Active immunity = B cells encounter antigens and produce antibodies against them Naturally acquired = bacterial and viral
infections Artificially acquired = vaccinations
Passive immunity = Antibodies received from immune human or animal donor temporary protection that ends when “borrowed antibodies” naturally degrade in the body Naturally acquired = mother’s antibodies cross
over placenta to fetus Artificially acquired = After receiving immune
serum or gamma globulin (used for treating rabies, hepatitis, snake bites, botulism, tetanus, etc.)
ANTIBODIES Also referred to as
immunoglobulins (Igs) Soluble proteins secreted
by activated B cells in response to an antigen capable of binding specifically to that antigen
Basic structure – four amino acid (polypeptide) chains linked by disulfide bonds
2 chains = Heavy chains, 2 chains = Light chains
Variable and constant regions
ANTIBODIES
Five major classes – IgM, IgA, IgD, IgG, IgE Remember – MADGE Slightly different biological roles Antibodies can function through:
Complement fixation = activated during nonspecific body defenses, antibodies attached to cellular targets cause the cell to lyse
Neutralization = antibodies bind to specific sites on bacteria or viruses, making them inactive
Agglutination = cross-linking between antibodies and antigens causes clumping
Precipitation = cross-linking makes clumps so big, they settle out of solution
CELL-MEDIATED RESPONSE
T cells are activated to form clones after binding with “recognized” antigen
Antigens must be “presented” by macrophages Different types of T cells:
Helper T cells = interact directly with B cells bound to antigens. They liberate lymphokines, chemicals that enhance the killing activity of macrophages, attract other leukocytes, or act as helper factors.
Cytotoxic (killer) T cells = directly attack and lyse infected and cancerous cells.
Delayed hypersensitivity T cells = release chemicals that enhance inflammation and promote a delayed allergic reaction
Suppressor T cells = terminate normal immune response by releasing suppressor chemicals
IMMUNITY DISORDERS
Allergy/hypersensitivity = overreaction to otherwise harmless antigen
Immunodeficiency = abnormalities in any immune element; example (AIDS)
Autoimmune disease = body’s self-tolerance breaks down, antibodies attack bodies own cells and tissues; example lupus