Lecture: The Lymphatic System Flashcards
What is the job of the lymphoid system?
Protect against disease (produce maintain distribute lymphocytes)
What 3 things cause the lymphoid system to respond?
Environmental pathogens Toxins Abnormal body cells, such as cancers
What role do lymphocytes play?
Identify, attack, and develop immunity as part of the immune response
What is immunity?
The ability to resist infection and disease
What makes a defense ‘nonspecific’
Blocks or attacks potential infectious organism but they cannot distinguish one attack from another.
What is lymph?
Interstitial fluid similar to plasma but does not have plasma proteins
What do lymphatic vessels do?
Carries lymph from peripheral tissues to the venous system
What 4 parts make up the lymphoid system?
Lymph, Lymphatic Vessels, Lymphoid tissues + organs, Lymphocytes and other cells
What 3 places are lymphocytes produces in?
Lymphoid tissues, Lymphoid organs, Red bone marrow
What 2 things do lymphocytes do?
Detects problems + travel to site of injury or infection
How do lymphocytes circulate?
From blood > Interstitial Fluid via capillaries > to venous blood via lymphatic vessels
How do fluids circulate?
Blood > Lymph > Venous system
What carries lymph?
Lymphatic Vessels
The lymphoid system begins with…?
Lymphatic Capillaries (the smallest vessels)
4 anatomical ways that lymphatic capillaries differ from blood capillaries?
- Start as pockets rather than tubes
- larger diameter
- thinner walls
- parts are flat or irregular
What is the structure of a lymphatic capillary?
Loosely bound, overlapping endothelial cells
How do the valves in lymphatic capillaries “work”
Overlap in endothelial cells act as 1 way valve, letting fluids, solutes, viruses and bacteria in, prevents return to intercellular space.
What is a lacteal?
Are special lymphatic capillaries in small intestine
What do lacteals do?
Transport lipids from digestive tract
What are the primary lymphoid organs?
Bone marrow + thymus
What are secondary lymphoid organs?
Lymph node, spleen, tonsils, peyers patches in intensive and appendix.
Lympathic vessels travel with _____?
Veins
Where is the vermiform appendix?
Right iliac or inguinal region.
What are deep lymphatics?
larger vessels that accompany deep arteries and veins
Superficial and deep lymphatics join to form what?
Lymphatic Trunks
Trunks empty into what two major collecting vessels?
thoracic duct right lymphatic duct
What is the Cisterna chyli?
a sac at the end of the thoracic duct
Where does the Cisterna chyli receive lymph from?
Right and left lumbar trunks + Intestinal trunk
Where does the inferior segment of thoracic duct collect lymph from?
The Left bronchio-mediastinal trunk, the Left subclavian trunk, the Left jugular trunk
Where is the thymus located?
In the mediastinum in front of the trachea
Where does the inferior segment of thoracic duct empty its contents?
The left subclavian vein
Where does the Right lymphatic duct college lymph from?
Right jugular trunk, Right subclavian trunk, and the Right bronchiomediastinal trunk
Where does right lymphatic duct empty its contents?
The right subclavian vein
What is Lymphedema?
Blockage of lymph drainage from a limb that causes severe swelling and Interferes with immune system function
Lymphocytes make up what percentage of circulating WBCs?
20-30%
Are most lymphocytes stored or circulating?
Stored.
What are the 3 classes of circulating lymphocytes?
T Cells, B cells, and NK cells.
Which type of lymphocyte is 80% of circulating lymphocytes?
T cells
What are the 3 types of T cells?
Cytotoxic, Helper + Suppressor
What do Cytotoxic T Cells do?
Attack cells infected by viruses and produce immunity
What do Helper T cells do?
Stimulate function of T cells and B cells
What do Suppressor T Cells do?
Inhibit function of T cells and B cells
What do Regulatory T Cells do?
Control sensitivity of immune response
What 2 types of cells make up Regulatory T cells?
Helper and suppressor T cells
What are some lesser known T cells?
Inflammatory T cells + Suppressor/inducer T cells
What cell type makes up 10-15% of circulating lymphocytes?
B cells
Where do T cells originate?
Via lymphoid stem cells that migrate to the thymus and diffrienciate after either thyme or thymopoeitin hormone are added.
After precursors of T cells are formed, where do they mature?
The thymus
Precursers of T cells are formed where?
Red bone marrow
What is the thymus?
A soft, triangular organ
What is the primary role of the thymus?
Receive immature T cells and train them into function mature T cells that attack only foreign cells.
What is a lymph node?
Tiny bean shaped mass of lymphoid tissue.
What is the job of the lymph node?
Filters the blood, uses specialized tissues to trap foreign antigens and destroy them.
Where are lymph nodes typically concentrated?
Near junctions of the major lymphatic vessels, in the neck groin and armpits.
What are plasma cells made from?
B cells
What do plasma cells do?
Produce antibodies (immunoglobulin proteins)
What is an antigen?
Targets that identify a pathogen or foreign compound
What are Immunoglobulin Proteins (Antibodies)?
The binding of a specific antibody to a specific antigen that initiates antibody-mediated immunity
Define “Antibody-Mediated Immunity”
A chain of events that destroys the target compound or organism
What is another name for Natural Killer (NK) Cells?
Granular lymphocytes
What cells make up 5-10% of circulating lymphocytes?
Natural Killer (NK) cells.
Which cells are responsible for immunological surveillance?
Natural Killer (NK) cells.
What do NK cells do?
Attack foreign cells, virus-infected cells, and cancer cells
How long can lymphocytes survive?
Many years
How do lymphocytes travel through tissues?
via blood vessels or lymphatics for transport
What is lymphopoiesis?
Lymphocyte production
What 3 things does lymphopoiesis involve?
Bone marrow, Thymus, Peripheral lymphoid tissues
Where are Hemocytoblasts?
Bone Marrow
What do Hemocytoblasts do?
divide into two types of lymphoid stem cells
What do Lymphoid Stem Cells that remain in the bone marrow produce?
B cells and natural killer cells
What do Lymphoid Stem Cells that migrate to the thymus produce?
T cells in environment isolated by blood-thymus barrier
Which cells migrate throughout the body to defend peripheral tissues?
T cells and B cells
What lymphocytes maintain their ability to divide?
T cells and B cells
What causes a lymphocyte to diffrenciate as a B cell?
exposure to hormone called cytokine (interleukin-7)
What causes a lymphocyte to diffrenciate as a T cell?
exposure to several thymic hormones
Which cells does the HIV virus kill?
Helper T cells
What are lymphoid tissues?
Connective tissues dominated by lymphocytes
What is a lymphoid nodule?
Areolar tissue densely packed with lymphocytes and germinal center containing dividing lymphocytes
What is the shape of an antibody?
Capital Y
What parts of the antibody bind to antigen?
The light + heavy chain or the “V” or of capital Y.
What is the region at the bottom of the “Y” shape of an antigen, below the “V”
Constant region
What are the 5 specific lymph nodes of the head and face? (Tonsils)
Pharyngeal tonsil, Left and Right Palatine tonsil, and the 2 Lingual tonsils.
Mucosa-Associated Lymphoid Tissue (MALT) is associated with what system?
The digestive system
What is Mucosa-Associated Lymphoid Tissue (MALT) located?
Aggregated lymph nodules deep to intestinal epithelial lining
What is the appendix made of?
a mass of fused lymphoid nodules
What separates the 5 tonsils / lymphoid organs from surrounding tissues?
a fibrous connective tissue capsule
What is the Trabeculae?
A bundles of collagen fibers that extend from capsule > inside lymph node
What is Hilum?
A shallow indent where blood vessels and nerves reach the lymph node
What does an Afferant lymphatic vessel do?
Carries lymph from peripheral tissues to lymph node
What does an Efferant lymphatic vessel do?
Carries lymph to venous circulation from lymph node at hilum.
The lymph node is a filter that removes ______?
Debris, Pathogens + 99% of antigens
What is the first step in immune response?
Antigens are extracted and ‘presented’ to lymphocytes, OR attached to dendritic cells to stimulate lymphocytes
Why are Lymphoid tissues and lymph nodes distributed all around the body?
To monitor peripheral infections before they reach the vital organs of trunk
Where are lymphatics located? (Dont say everywhere)
- Skin
- Mucous membranes
- Serous membranes lining cavities
Stem cells that remain in Bone Marrow turn into what 2 types of cells?
B cells and NK cells
How are lymphoid nodules distributed throughout the body?
- Lymph Nodes
- Spleen
- Resp Tract (tonsils)
- Digestive Tract
- Urinary Tract
Trace the flow of lymph through the node from afferent lymphatic to efferent
subscapular space > outer cortex > deep cortex > core/medulla > hilum
What is inside the subscapular space of the lymph node?
macrophages and dendritic cells
What is inside the outer cortex of the lymph node?
B cells within germinal centers
What is inside the deep cortex of the lymph node?
T cells
What is inside the core (medulla) of the lymph node?
B cells and plasma cells, organized into medullary cords
Which lymph nodes protect the digestive and respiratory systems?
Nodes of Gut, Trachea, Lungs, and Thoracic Duct
What is Lymphadenopathy?
Chronic or excessive enlargement of lymph nodes. Indicate infections, endocrine disorders, or cancer
When does the thymus atrophy?
After puberty
What divides the two thymic lobes?
The septa
Where do T cells go after diffrenciating in the Thymus?
Into medulla via medullary blood vessels
What is a thymic lobule?
a subdivision of the thymic lobe. comprised of a dense outer cortex and a pale central medulla
What surrounds lymphocytes in the cortex of the thymus?
Reticular epithelium
What maintain blood–thymus barrier in the cortex of the thymus?
Reticular epithelium
The reticular epithelium of the thymus secretes what and what does it do?
thymic hormones that stimulate stem cell divisions and T cell differentiation
What are thymic (Hassall) corpuscles?
Concentric layers of reticular epithelium in the medulla
What is Thymosin?
a thymic hormone that promotes development of lymphocytes
What are 3 functions of the spleen?
- Phagoticises abnormal blood cells and other blood components
- Storage of iron recycled from RBC
- Initiation of immune responses by B cells and T cells in response to antigens
What is the gastrosplenic ligament?
A ligament attaching the spleen to the stomach
Where do splenic veins, arteries, and lymphatic vessels attach to the spleen?
At the hilum
What organ has red and white pulp?
The spleen
Why is red pulp red? Why is white pulp white?
Red: Due to RBC’s White: resembles lymphoid nodules
White pulp surrounds fine branches of what?
Trabecular Arteries
Describe the 3 steps of splenic circulation
Blood passes through
Network of reticular fibers> sinusoids lined w macrophages > empties into trabecular veins
3 aspects of “Specific Defenses”
- Protect against specific pathogens
- Depend on activities of lymphocytes
- Specific resistance (immunity after exposure)
7 categories of non-specific defenses (Please Pass It, I Can’t Idle Forever)
- Physical barriers
- Phagocytes
- Immunological surveillance
- Interferons
- Complement
- Inflammatory response
- Fever
What are Interferons?
Chemical messengers that trigger production of antiviral proteins in normal cells
What do antiviral proteins do?
Block replication.
3 ways Fever helps the immune response?
- Increases body metabolism
- Accelerates defenses
- Inhibits some viruses and bacteria
What is “Complement”
- breaks down cell walls
- attracts phagocytes
- stimulates inflammation
Examples of Physical Barries?
Hair, Skin, Mucous that washes away or break down microorganisms via enzymes or stomach acid
What are Microphages?
Neutrophls and eosinphils
What do microphages do?
Leave the bloodstream and enter peripheral tissues to fight infections
What system are macrophages a part of ?
The monocyte–macrophage system
How to Activated Macrophages respond to pathogens?
- Engulf pathogen and destroy with lysosomal enzymes
- Bind to pathogen
- Destroy pathogen by releasing toxins into interstitial fluid
What are histiocytes and where might you find them?
A fixed macrophage, stays in specific tissues or organs such as dermis and bone marrow
What is another name for a fixed macrophage?
histiocytes
A macrophage that travels throughout the body
Free macrophage
2 examples of special histiocytes?
Microglia (CNS), Kupffer cells (Liver Sinusoids)
What is Chemotaxis?
The attraction or repulsion of cells by chemicals in surrounding fluids
Describe phagocytosis
A Phagocyte adheres to target, and surrounds it with a vesicle… gulp!
What is perforins?
The chemical released by the vesicle in an NK cell when lysing an abnormal cell. (could be a cancer cell too)
What is immunological escape?
When cells such as cancer cells avoid NK cells.
What are cytokines?
Chemical messengers released by tissue cells
What are 3 types of Interferons?
Alpha Beta and Gamma Interferons
Alpha interferons, produced by what and do what?
Produced by Leukocytes, Stimulate NK cells
Beta interferons, produced by what and do what?
Secreted by fibrocytes, Slow inflammation
Gamma interferons, produced by what and do what?
Secreted by T cells and NK cells, Stimulate macrophage activity
How many complement proteins are in plasma?
11
What are the 2 pathways of the complement cascade?
- classical pathway (fast) 2. alternative pathway (slow)
How do both pathways of complement end?
Conversion of inactive complement protein C3 into the active form, C3b
What is opsonization
A process by which a foreign particle/antigen, is coated opsonins to facilitate phagotization.
The membrane attack complex (MAC) is part of what process?
Complement
What might be going on if you experience Swelling, Redness, Heat, and Pain?
Inflammation
3 Products of Inflammation?
Necrosis, Pus, Abscess
What temp constitutes a fever?
37°C (99°F) +
What is a Pyrogens?
Any material that causes the hypothalamus to raise body temperature
3 types of specific defenses?
- Specific resistence (Immunity) 2. T cell (cell mediated immunity) 3. B cell (humoral / antibody immunity)
4 forms of Immunity
- Innate (Present at birth)
- Acquired (After birth)
- Active (Antibodies develop after exposure to antigen)
- Passive (Antibodies are transferred from another source)
Vaccines are an example of
Induced Active Immunity
Acquisiton of antibodies through breast milk is an example of?
Naturally acquired Passive Immunity
4 properties of Immunity
- Specificity 2. Versatility 3. Memory 4. Tolerance
T cells only recognize antigens that are …?
Nound to glycoproteins (MHC Proteins) in plasma membranes
What is responsible for activating T cells against foreign cells and proteins?
Antigen-Presenting Cells (APCs)
Free and fixed macrophages, Kupffer cells and Microglia are all examples of
Phagocytic Antigen Presenting Cells
2 examples of Non-phagocytic (pinocytic) APCs ?
Langerhans cells (skin) + Dendritic cells (lymph nodes and spleen)
What are the 3 actions of Cytotoxic T cells:?
- Release perforin: destroy antigenic plasma membrane
- Secrete poisonous lymphotoxin: destroy target cell
- Activate genes in target cell: That cause cell to die
What is the roll of memory T cells?
“remembers” an antigen and stays in circulation, forms cytotoxic T cells if antigen is redetected
When do suppressor T cells go to work?
AFTER the immediate immune response
What happens during B Cell Sensitization?
antigens are taken into the B cell and processed. Then they reappear on surface, bound to Class II MHC protein
What stimulates a sensitized B cell into an active B cell?
a helper T cell activated by same antigen
What happens during B cell activation?
Help T binds to MHC complex a secretes cytokines that promote B cell division
What is produced during B cells division?
Plasma cells + Memory B cells
What does the constant vs variable segment on the antibody do?
Determine five types of antibodies vs SPECIFIC antibody molecule
What does an antigen binding site of an antibody bind to?
antigenic determinant sites of antigen
The free tips of two variable segments of an antibody serve as what?
an antigen binding site
What is it called when an antibody is bound to an antigen?
Antigen-Antibody Complex
Exposure to What leads to B cell sensitization and Immune response?
Exposure to a complete antigen
What is Hapten and why is it dangerous?
A partial antigen, it attaches to a carrier molecule to form a compelete antigen. But if attacked, the carrier molecule will also be destroyed.
7 Functions of Antigen-Antibody Complex
No person can attract optimal Ideal people (buttsvagina)
- Neutralize antigen-binding sites
- Precipitation and agglutination
- Complement
- Attracts phagocytes
- Opsonization
- Inflammation
- Prevents bacterial and viral adhesion
What is the difference between Primary and Secondary Responses to Antigen Exposure?
Primary: Takes time to develop, Antigens activate B cells, Plasma cells differentiate
Antibody (level) slowly rises (Igm antibody, fast but less effective)
Secondary: Activates memory B cells at lower antigen concentrations, Immediately secretes antibodies in massive quantities (Igb antibody, slow and effective)
1st step of a bacterial infection
NK’s and Neutrophils begin killing bacteria
How is the immue systems response to a bacterial infection vs a viral infection different?
During a viral infection, cytotoxic T cells and NK cells are activated by contact with virus-infected cells
At what pregnancy age does a fetus have an immune system?
3-4 months
What antibodies will a 4 month old fetus produce?
IgM
Where does a fetus produce B cells?
In the liver and bone marrow
What antibodies does mothers milk produce?
IgA
What provides passive immunity to a fetus?
Maternal IgG antibodies passing through placenta
By what age do Antibody, B cell, and T cell levels rise to adult levels?
12
What is an autoimmune disorder?
A malfunction of system that recognizes and ignores “normal” antigens.
What are autoantibodies?
antibodies that work against body cells, made by activated b cells as part of an autoimmune disorder.
3 examples of autoimmune disorders?
- Thyroiditis 2. Rheumatoid arthritis 3. Insulin-dependent diabetes mellitus (IDDM)
What causes immunideficiency disorders?
- bad embryological development of lymphoid tissues
- viral infections (HIV)
- Immunosuppressant drugs
What is an allergen / allergy?
Allergens trigger allergies, an excessive immune response to antigens.
Type 1 allergy:
immediate hypersensitivity, the most common type of allergy. A rapid and severe response . (environmental allergies)
What causes production of large quantities of IgE antibodies distributed throughout the body ?
Type I Allergy Sensitization
What can cause may cause anaphylaxis?
a large quantity of allergens in the blood stream.
What is anaphylactic shock?
Peripheral vasodilatation that can cause circulatory collapse
Why is chronic stress bad for the immune system?
Causes a secretion of Glucocorticoids which inhibit the immune system. In the long term it lowers resistence.
4 affects of aging on the immune response?
- low Thymic hormone production
- T cells become less responsive to antigens
- Fewer T cells = less responsive B cells
- Immune surveillance against tumor cells declines
What 2 other systems adjust the sensitivity of immune response?
Nervous and Endocrine Systems
