Terms in this set (58)
List the parts of the lymphatic system (8), and list the three main functions of the lymphatic system.
-PARTS: lymph, lymphatic vessels, lymphatic tissue, lymphatic nodules, lymph nodes, tonsils, the spleen, and the thymus.
1. Fluid balance (fluid that doesn't transfer from interstitial space back to blood capillaries goes into lymphatic capillaries where fluid is called lymph)
2. Fat absorption (absorbs fats and other substances through lacteals in the digestive tract)
3. Defense (microorganims and other foreign substances are filtered from lymph by lymph nodes and from blood by the spleen)
Define lymph. How is it formed?
clear or yellowish fluid derived from interstitial fluid and found in lymph vessels (the small amount of fluid not absorbed back into the blood capillaries)
What is the function of lacteals?
Lymphatic vessel in the wall of the small intestine that carries chyle (fatty lymph) from the intestine and absorbs fat. (fat is absorbed by the lymphatic system in digestive tract)
Describe the structure of a lymphatic capillary. Why is it easy for fluid and other substance to enter a lymphatic capillary?
They are tiny, closed-ended vessels consisting of simple squamous epithelium. Since they lack a basement membrane and the cells of the epithelium slightly overlap and are attached loosely to one another. They are far more permeable than blood capillaries and nothing in the interstitial fluid is excluded from the lymphatic capillaries.
What is the function of the valves in lymphatic vessels? Name 3 mechanisms responsible for the movement of lymph through the lymphatic vessels.
-The over-lapping epithelium creates a series of one-way valves that allow fluid to enter capillary but not go back into interstitial fluid.
-3 mechanisms: (1) periodic contraction of smooth muscle in lymphatic vessel wall (2) contraction of surrounding skeletal muscle during activity (3) pressure changes in the thorax during respiration
Where does lymph return to the blood? What areas of the body are drained by the right lymphatic and thoracic ducts?
Lymphatic vessels converge and empty into blood at two locations:
1. right lymphatic duct (includes upper right limb and right half of head, neck and chest) which connects to right subclavian vein
2. thoracic duct (includes lymphatic vessels from everywhere else) which empties into the left subclavian vein
What are the function of lymphocytes and reticular fibers in lymphatic tissue?
-Lymphocytes are a type of white blood cell. The two types are B cells and T cells which divide, increase in number, and are part of the immune response when body is exposed to microorganisms/foreign substances.
-Reticular fibers act as attachment sites for lymphocytes and other cells. When lymph or blood filters through lymphatic organs, the fiber network traps microorganisms and other particles in the fluid.
Define diffuse lymphatic tissue, lymphatic nodules, and Peyer's patches
-diffuse lymphatic tissue has no clear boundary, blends in, and contains dispersed lymphocytes, macrophages, and other cells. It is located deep to mucous membranes, around lymphatic nodules, and within the lymph nodes and spleen.
-lymphatic nodules are denser arrangements of lymphatic tissue. Numerous in the loose CT of the digestive, respiratory, urinary, and reproductive systems.
-Peyer's patches are lymph nodules found in the lower half of the small intestine and the appendix
Describe the structure, function, and location of the three groups of tonsils
Palatine tonsils (aka "the tonsils") are located on each side of the posterior opening of oral cavity; pharyngeal tonsil (called adenoid when enlarged) is located near the internal opening of nasal cavity; lingual tonsil is on the posterior surface of tongue. All are groups of lymphatic nodules and diffuse lymphatic tissue that provide protection against bacteria/harmful material entering pharynx from nasal or oral cavities.
Where are lymph nodes found? Describe the parts of a lymph node, and explain how lymph flows through a lymph node.
-They are distributed along the course of the lymphatic vessels. Superficial lymph nodes (inguinal, axillary, and cervical nodes) are in subcutaneous tissue and deep lymph nodes are everywhere else.
-Afferent lymphatic vessels carry lymph to the lymph nodes to be filtered and efferent lymphatic vessels carry lymph away from the nodes
What are the functions of lymph nodes? What is a germinal center?
They are the only structures to filter lymph (removing bacteria and other materials). Lymphocytes congregate, function, and proliferate within lymph nodes. Germinal centers are the lighter-straining center of a lymphatic nodule where rapid lymphocyte division (production) occurs.
Where is the spleen located? Describe white and red pulp.
-The spleen is located in the left, superior corner of the abdominal cavity
-The reddish brown substance of the spleen is RED pulp. It's associated with VEINS and consists of splenic cords and venous sinuses.
-WHITE pulp is diffuse lymphatic tissue and lymphatic nodules surrounding the ARTERIES within the spleen
Where does blood enter and exit the red pulp?
Blood goes from arteries in lymphatic nodule (white pulp) and either connects directly to venous sinuses, quickly crosses the gap to the sinuses, or empties into splenic cords and passes through walls of sinuses (RED PULP). The venous sinuses connect to a branch of a the splenic vein.
What are three functions of the spleen?
1. Destroy's defective red blood cells.
2. Detects and responds to foreign substances in blood.
3. Functions as a blood reservoir, holding a small volume of blood that can be used in situations such as exercise.
Where is the thymus located? Describe its structure and function.
Located in the superior mediastinum. A capsule surround each lobe and trabeculae extend from capsule into substance of gland to divide it into lobules. The thymic tissue consists of epithelial cells and the cell processes are joined by desmosomes to form small, irregularly shaped compartments filled w lymphocytes. The thymus is the site of the MATURATION OF T CELLS and although large number of lymphocytes are produced here, most are degenerate.
Definite immunity, specificity, and memory
1. immunity- ability to resist damage from foreign substances such as microorganisms, harmful chemicals, and internal treats (ex. cancer).
2. specificity- the ability of adaptive immunity to recognize a particular substance (ex. can distinguish among various types of bacteria)
3. memory- ability of adaptive immunity to "remember" previous encounters w a particular substance so the response is faster and stronger and lasts longer
What are the differences between innate and adaptive immunity?
-All multicellular organisms have some degree of innate immunity which is a response that is the same with each exposure to an antigen- there is no ability for the system to remember a previous exposure so response can be modified.
-In adaptive immunity, the body recognizes and destroys foreign substances, but the response to them improves each time the substance is encountered.
List the four main components of innate immunity
1. mechanical mechanisms
2. chemical mediators
4. inflammatory response
Name two mechanical mechanisms that prevent the entry of microorganisms into the body.
1. skin and mucous membranes form barriers that prevent their entry.
2. tears, saliva, and urine wash them from body surfaces
What is complement? In what two ways is it activated? How does complement provide protection?
-Complement is a group of serum (fluid portion of blood when formed elements are removed) proteins that stimulates phagocytosis and inflammation.
-It is activated by either the classical (adaptive imm) or alternative pathway (innate imm) in the complement cascade... a series of reactions in which each component activates the next component.
-Provides protection by: membrane attack complex (MAC) which results in lysis (rupture) of cells; stimulation of macrophages to phagocytize the bacteria by attaching to bacterial cells; and by the proteins attracting immune system cells to sites of infection and promote inflammation.
What are interferons? How do they provide protection against viruses?
Interferons are proteins that are produced and released from infected cells as a "warning;" they bind to neighboring cells and stimulate them to produce antiviral proteins to stop the spread of the virus. Interferons do not protect the cell that produces them.
Define chemotaxis and phagocytosis.
-Chemotaxis is the movement of white blood cells towards chemicals released from microorganisms or damaged tissues (important chemicals include complement, leukotrienes, kinins, and histamine).
-Phagocytosis is the endocytosis (bulk uptake of material through the cell membrane) and destruction of particles by cells called phagocytes (particles can be microorganisms or their parts, foreign substances, or dead cells from body). Most important phagocytic cells are neutrophils and macrophages.
What are the functions of neutrophils and macrophages? What is pus?
-Neutrophils are small, phagocytic white blood cells. They are usually the first cells to enter infected tissues in large numbers. They release chemical signs that increase the inflammatory response by activating other immune cells.
-Macrophages are the most effective phagocytes; important in later stages of infection and in tissue repair; located throughout the body to "intercept" foreign substances; processes antigens; involved in the activation of B and T cells
-Pus is an accumulation of dead neutrophils, dead microorganisms, debris from dead tissue, and fluid
What effects are produced by the chemicals released from basophils, mast cells, and eosinophils?
Basophils and mast cells release chemicals that produce an inflammatory response or activate other mechanisms, such as smooth muscle contraction in the lungs. Eosinophils release enzymes that break down chemicals released by basophils and mast cells (they contain and reduce the inflammatory response)
Describe the function of NK cells.
account for up to 15% of lymphocytes; recognize classes of cells (tumor or virus infected cells) in general, rather than specific cells, and use a variety of methods to kill their target cells. Classified as part of innate immunity due to generalized function and lack of memory response.
Describe the events that take place during an inflammatory response.
(1) Bacteria or damage to tissues causes the release or activation of chemical mediators (2) chemicals produce several effects such as chemotaxis, increased vascular permeability and increased blood flow (vasodilation)
(3) Chemical mediators are released and phagocytes/other WBC are attracted until bacteria are destroyed
(4) Phagocytes remove microorganisms and dead tissue, and the damaged tissues are repaired.
What are the symptoms of local and systemic inflammation?
-Local inflammation (confined to a specific area of the body) symptoms include redness, heat, swelling, pain and loss of function.
-Systemic inflammation (occurs in many parts of the body) has same symptoms as above as well as the red bone marrow produces and release large numbers of neutrophils (promote phagocytosis); pyrogens, "fire-producing", (chemicals released by lymphocytes, macrophages, neutrophils and other cells) stimulate fever production; and in severe cases, increased vascular permeability is so widespread that large amounts of fluid are lost from the blood into the tissues (the decreased blood volume can cause shock and death).
Define antigen. Distinguish between a foreign antigen and a self-antigen.
-antigens are substances that stimulate adaptive immunity.
-foreign antigens are not produced by the body but are introduced from outside it (ex. bacteria and virus components, pollen, foods, drugs, etc)
-self-antigens are molecules produced by the body that stimulate an adaptive immune system response (can be beneficial or harmful)
What are allergic reactions and autoimmune diseases?
-Allergic reactions occur when foreign antigens trigger an overreaction of the immune system.
-Autoimmune diseases results when self-antigens stimulate unwanted tissue destruction.
What types of lymphocytes are responsible for antibody-mediated and cell-mediated immunity?
antibody-mediated: B cells
cell-mediated: T cells
Describe the origin and development of B and T cells.
both are derived from stem cells in the red bone marrow. Pre-T cells migrate through blood to thymus to divide and be processed into T cells (thymus produces hormones such as thymosin which stimulates T-cell maturation). Pre-B cells are processed in the red bone marrow into B cells.
Distinguish between positive and negative lymphocyte selection. What are lymphocyte clones?
-Positive selection results in survival of pre-B and T cells that are capable of immune response.
-Negative selection eliminates or suppresses lymphocytes acting against self-antigens (prevents destruction of one's own cells).
-The B and T cells that can respond to antigens are composed of small groups of identical lymphocytes called CLONES (each clone can only respond to a particular antigen)
What happens to lymphocytes after they are produced in red bone marrow or the thymus?
They move through the blood to the lymphatic tissue.
*approx 5 T cells for every B cell in blood
Define antigenic determinant and antigen receptor. How are they related to each other?
-Antigenic determinant (epitopes) are specific regions of a given antigen recognized by a lymphocyte (antigens has many different antigenic determinants)
-Antigen receptors are on the surfaces of lymphocytes of a given clone (identical) and they combine with a specific antigen determinant. (any given antigenic determinant can combine only with a specific antigen receptor)
What type of antigens are displayed by MHC class I and II molecules?
-class I: display antigens produced inside the cells on their surfaces.
-class II: (antigen-presenting cells) take in foreign antigens by endocytosis then display them on the surface of the cell for other immune cells to respond
What type of cells display MHC class I and II antigen complexes, and what happens as a result?
-Class I molecules are found on nucleated cells; they display antigens produced inside the cells on their surfaces. (results in cell destruction)
-Class II are found on antigen-presenting cells (B cells, macrophages, monocytes, and dendritic cells) which take in foreign molecules by endocytosis and then transported to surface of cell to be displayed to other immune cells. (does not destroy cell... stimulates other immune system cells to respond to antigen)
both antigen and the individual organisms own MHC molecule are required to activate T cells
What is costimulation? State two ways in which it can happen.
additional signals required to produce a response from a B or T cell (in addition to the MHC class II complex with an antigen receptor). It is accomplished by cytokines (such as interleukin-1) and by molecules attached to the surface of cells.
Why are helper T cells sometimes called CD 4 or T4 cells? Why are cytotoxic T cells sometimes called CD 8 or T8 cells?
-helper T cells have a glycoprotein called CD4 or T4, which helps to connect helper T cells to the macrophage by binding to MHC molecules
-cytotoxic T cells have a glycoprotein called CD8 or T8 which helps connect cytotoxic T cells to cells displaying MHC molecules
Describe how antigen-presenting cells stimulate an increase in the number of helper T cells. Why is this necessary?
When interleukin-1 (released by macrophage) attaches to interleukin-1 receptors, it stimulates the helper T cell to secrete the cytokine interleukin-2 and to produce interleukin-2 receptors. The helper T cell then stimulates itself to divide when interleukin-2 binds to interleukin-2 receptors. The "daughter" helper T cells can then divide again if they are exposed to the same antigen that stimulated the "parent" helper T cell. This greatly increases the number of helper T cells.
**IMPORTANT BECAUSE.... helper T cells are necessary for the activation of most B and T cells.
Describe how helper T cells stimulate an increase in the number of B or T cells. Why is this necessary?
B cells take in the same antigen that activated the helper T cell by endocytosis. The B cell then used MHC class II molecule to present the processed antigen and the T cell receptor binds to the MHC class II/antigen complex. (there is costimulation of the B cell by CD4 and other surface molecules and by interleukins released from the helper T cell). This stimulates the B cell to divide and the resulting daughter cells to divide and so on... producing many cells that recognize the same antigen.
**IMPORTANT BECAUSE...The daughter cells differentiate to become plasma cells that produce antibodies which is part of the immune response that eliminates the antigen.
What is tolerance? List three ways it is accomplished.
A state of unresponsiveness of lymphocytes to a specific antigen. Although foreign antigens can induce tolerance, the most important function of tolerance is to prevent the immune system from responding to self-antigens. Tolerance can be induced by:
1. Deletion of self-reactive lymphocytes (prenatal development and after birth)
2. Prevention of the activation of lymphocytes (preventing either the MHC/antigen complex binding w an antigen receptor or costimulation... both required for lymphocyte activation
3. Activation of suppressor T cells (suppress immune responses with suppressive cytokines or killing antigen-presenting cells)
Antibody-mediated immunity is effective against what kinds of antigens?
Effective against extracellular antigens (such as bacteria, viruses that are outside cells and toxins) since antibodies are in body fluids.
What are the functions of the variable and constant regions of an antibody? List the five classes of antibodies, and state their functions.
-The variable regions (the end of each "arm" of antibody) attaches to antigen and constant region (the rest of antibody) can do things such as activate complement, attach antibody to cells such as macrophages, basophils, and mast cells, etc...
-5 classes of antibodies... IgG, IgM, IgA, IgE, and IgD
Describe the direct and indirect ways in which antibodies affect antigens.
-Direct effects occur when a single antibody binds to antigen and inactivates the antigen or when many antigens are bound together and are inactivated by many antibodies.
-Indirect effects (results in the most of the effectiveness of antibodies) occurs after an antibody has attached by its variable region to an antigen, then the constant region of the antibody can activate other mechanisms that destroy the antigen.
What are plasma cells and memory cells, and what are their functions?
-Plasma cells produce antibodies
-Memory cells are responsible for the secondary (memory response) which occurs when the immune system is exposed to an antigen against which it has already produced a primary response. (ARE THE BASIS FOR ADAPTIVE IMMUNITY)
What are the primary and secondary antibody responses? Why doesn't the primary response prevent illness but the secondary response does?
-The primary response results from the first exposure of a B cell to antigen. B cells form plasma cells, which produce antibodies and memory B cells (slower and disease symptoms show because of the length of time required to produce enough antibodies to be effective against antigen).
-The secondary response occurs when the immune system is exposed to an antigen against which it has already produced a primary response. Memory B cells quickly form plasma cells and additional memory B cells (B memory cells quickly divide to form plasma cells which rapidly produce antibodies... person is immune bc of quickness).
Cell-mediated immunity is effective against what kinds of antigens?
Effective against microorganisms that live inside the cells of the body (essential for fighting viral infections!!)
How do intracellular microorganisms and helper T cells stimulate cytotoxic T cells?
Intracellular microorganisms are broken down and become processed antigens that are combined with MHC class I molecules and displayed on the surface of infected cell. That with costimulation provided by helper T cells that release cytokines (i.e. interleukin 2).... stimulates activation and cell division of cytotoxic T cells.
How is long-lasting immunity achieved in cell-mediated immunity?
long-lasting memory in cell-mediated immunity is achieved in the same way as in memory B cells... memory T cells provide a secondary response and long-lasting immunity (quicker and more efficient after first exposure)
State the two main responses of cytotoxic T cells.
1. Destroy infected cell by lysis (perforin protein of cytotoxic t cells forms a channel in the plasma membrane of the target cell causing water to enter and the cell to burst)
2. Cytotoxic T cells release cytokines that activate additional components of the immune system.
What kind of immune response is produced by delayed hypersensitivity T cells?
Delayed hypersensitivity T cells respond to antigens by releasing cytokines... therefore, they promote phagocytosis and inflammation, especially in allergic reactions.
Describe how interactions among innate, antibody-mediated, and cell-mediated immunity can eliminate an antigen.
There is only one immune system... these categories are artificial divisions used to emphasize particular aspects of immunity. However, immune responses often involve components of more than one type of immunity. (ex. although adaptive immunity can recognize/remember specific antigens, after recognition, many aspects of destruction are innate immunity activities.
What is immunotherapy? Give examples.
Immunotherapy treats disease by altering immune system function or by directly attacking harmful cells. (ex. administering cytokines or other agents can promote inflammation & activation of immune cells which can help destroy tumor cells; inhibiting immune system for ppl with multiple sclerosis by using interferon beta to block the expression of MHC molecules that display self-antigens)
Distinguish between natural and artificial immunity and between active and passive immunity.
-Natural: contact with an antigen or antibody occurs as part of everyday living & is not deliberate
-Artificial: (immunization) a deliberate introduction of an antigen or antibody into the body
-Active: individual's own immune system is the cause of the immunity (whether or not is naturally or artificially exposed to an antigen)
-Passive: occurs when another person or an animal develops antibodies and the antibodies are transferred to a nonimmune individual
State four general ways of acquiring adaptive immunity. Which two provide the longest-lasting immunity?
-active natural (longest-lasting)
-active artificial (longest-lasting)
(passive immunity is not long-lasting because the individual does not produce his or her own memory cells)
What effect does aging have on the major functions of the lymphatic system?
Aging has little effect on the ability of the lymphatic system to remove fluid from tissues, absorb fats from the digestive tract, or remove defective red blood cells from the blood
Describe the effects of aging on B cells and T cells. Give examples of how they affect anti-body mediated immunity and cell-mediated immunity responses.
-little effect on the ability of B cells to respond to antigens and # of circulating B cells remains stable in most
-thymic tissue is eventually replaced with adipose tissue so the ability to produce new, mature T cells in the thymus is eventually lost (number of T cells still remains stable, though, bc they can still replicate-just not maturation)
-Decreased helper T cell proliferation (division) results in decreased antibody-mediated immunity and cell-mediated immunity responses to antigens
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