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Immune System
Anatomy & Physiology
| Question | Answer |
|---|---|
| immune system | protects from infectious agents & harmful substances (typically w/o awareness), composed of numerous cellular and molecular substances that function together to provide us with immunity, and its function is dependent on specific types of infectious agents |
| infectious agents | organisms that cause damage or death to host organism |
| pathogenic | a term used to describe infectious agents that cause harm |
| five major categories of infectious agents | bacteria, viruses, fungi, protozoans, and multicellular parasites |
| bacteria | single-celled organism, 1-2 micrometers, enclosed by cell wall, come in multiple shapes (spherical [cocci], rodlike [bacilli], coiled [spirilla]), and there are good and bad types |
| examples of diseases caused by bacteria | streptococcal infection (strep throat), tuberculosis, and Lyme disease |
| Viruses | acellular organisms that are composed of DNA or RNA within a protein shell, and they are smaller than bacteria (one-hundredth of a micrometer), and are obligate intracellular parasites |
| obligate intracellular parasites | must enter cell to reproduce, viral particles formed within infected cells, released from them to infect surrounding cells, and cell can be ultimately killed by virus or immune system |
| examples of diseases caused by a virus | depends partly on type of infected cell (i.e. chicken pox, HIV, common cold) |
| fungi | have cell wall external to plasma membrane, includes molds, yeasts, multicellular fungi, release proteolytic enxymes |
| proteolytic enzymes | induce inflammation causing redness and swelling |
| fungal diseases | in U.S. usually limited to superficial infections of skin, scalp, nails (i.e. ringworm and athlete's foot), others can infect mucosal linings or internal infection |
| protozoans | lack cell walls, are intracellular and extracellular parasites, and have the ability to move (with cilia) |
| protozoan disease examples | malaria, trichomoniasis |
| multicellular parasites | nonmicroscopic organisms that reside in host from which they take nourishment |
| example of parasitic diseases | parasitic worms such as tapeworms infect intestinal tract of humans and other mammals |
| leukocytes | formed in the red bone marrow, include three types of granulocytes, include monocytes, and include lymphocytes |
| types of granulocytes | neutrophils, eosinophils, and basophils |
| monocytes | become macrophages when take up residence in the tissues |
| lymphocytes | B-lymphocytes, T-lymphocytes, NK (natural killer) cells |
| structures that house immune system cells | most found not in the blood but in lymphatic tissue, select organs, epithelial and mucosal membranes, and connective tissue |
| lymphatic tissue | lymph nodes, spleen, tonsils, MALT, lymphatic nodules |
| lymphatic tissue | where many T- and B-lymphocytes, macrophages, NK cells are housed |
| select organs | macrophages also housed in other organs, some specifically named based on location (i.e. alveolar macrophages of lung, microglia of brain), may be permanent residents (fixed macrophages), and may migrate through tissues as wandering macrophages |
| epithelial layers of skin and mucosal membranes | dendritic cells here that derived from monocytes engulf pathogens in skin and mucosal membranes and migrate to lymph node through lymph vessels |
| connective tissue | mast cells located here, typically in close proximity to small blood vessels, abundant in dermis, and abundant in mucosa of respiratory, digestive, and urogenital tracts |
| two categories of the immune system | innate immunity and adaptive immunity |
| the two types of immune systems are... | organized based on type of immunity provided and work together to protect from harmful agents |
| how the two types of immune systems differ | cells involved, specificity of cell response, mechanisms of eliminating harmful substances, and amount of time for response |
| innate immunity | protects against numerous different substances, born with these defenses, does not require previous exposure to a foreign substance, and respond immediately to potentially harmful agent. |
| innate immunity includes | barriers of the skin and mucosal membranes, nonspecific cellular and molecular internal defenses |
| adaptive immunity | involves specific T-lymphocytes and B-lymphocytes, provides powerful means of eliminating foreign substances, and takes several days to be effective |
| T-lymphocytes and B-lymphocytes | respond differently to different foreign substances (i.e. particular lymphocytes responds to chickenpox virus |
| structures of innate immunity | prevent entry of potentially harmful substances, respond nonspecifically to wide range of harmful substances and include the first two lines of defense |
| first line of defense | skin and mucosal membrane |
| second line of defense | internal processes of innate immunity, activities of neutrophils, macrophages, NK cells, chemicals such as interferon and complement, and physiological processes such as inflammation and fever |
| physical barrier of skin | formed by epidermis and dermis, few microbes able to penetrate, has natural flora (nonpathogenic microorganisms residing here, help prevent growth of pathogenic microorganisms) |
| mucosal membrane barrier | membranes lining openings of the body, produce mucin (when hydrated, forms mucus), lined by harmless bacteria |
| barrier defenses | mechanisms usually successful, but infectious agents may enter if the barrier is compromised or there are too many microbes (this activates the innate immunity and adaptive immunity) |
| neutrophils and macrophages | cells of innate immunity |
| neutrophils | most prevalent leukocyte in blood, first to arrive during inflammatory response, and fights off bacteria |
| macrophages | reside in tissues throughout the body, arrive later and stay longer than the neutrophils, engulf unwanted substances through phagocytosis |
| basophils and mast cells | proinflammatory chemical-secreting cells that release substances to increase fluid movement from blood to injured tissue and are chemotactic |
| basophils | circulating in blood |
| mast cells | reside in connective tissue, mucosa, and internal organs |
| chemotactic | describes attracting immune cells as part of inflammatory response |
| granules released by basophils and mast cells during inflammatory response... | contain histamine and heparin |
| histamine | increases vasodilation and capillary permeability |
| heparin | anticoagulant |
| eicosanoids | released from the plasma membrane of basophils and mast cells and increase inflammation |
| natural killer cells | destroy wide variety of unwanted cells (i.e. virus/bacteria-infected cells, tumor cells, transplanted tissue cells), formed in bone marrow & circulate in blood, accumulate in secondary lymphatic structures, and patrol the body detecting unhealthy cells |
| immune surveillance | the patrolling of the body detecting unhealthy cells that is conducted by the natural killer cells |
| natural killer cells | destroy unhealthy cells by releasing cytotoxic chemicals (include perforin and granzymes) |
| perforin | forms transmembrane pore in unwanted cells |
| granzymes | initiate apoptosis |
| apoptosis | form of cellular death |
| eosinophils | target parasites, degranulation and release of enzymes and other substances, participate in immune response of allergy and asthma, and engage in phagocytosis of antigen-antibody complexes |
| inflammation | immediate, local, nonspecific response, occurs in vascularized tissue against variety of stimuli, major effector of innate immunity, and helps eliminate infectious agents from body |
| stimuli that ellicit inflammation | scratch of skin, bee sting, overuse of body structure |
| first event of inflammation | numerous chemicals are released from injured tissue, basophils, mast cells, and infectious organisms (including histamine, leukotrienes, prostaglandins, chemotactic factors) |
| second event of inflammation | released chemicals causing responses in local blood vessels, vasodilation (increased capillary permeability) |
| third event of inflammation | leukocytes recruited to the area |
| effects of inflammation | increased fluid, protein, immune cells leaving capillaries, delivers substances needed to eliminate pathogens and promote healing, raises hydrostatic pressure |
| effects of inflammation continued... | net movement of fluid from blood through infected area exudates additional fluid uptake by lymphatic capillaries, carries away infectious agents, dead cell, cellular debris, and lymph monitored as passes through lymph nodes |
| effects of inflammation within 72 hours (inflammatory response slowing down) | monocytes exit blood, become macrophages, & begin cleaning up affected area, bacteria, damaged host cells, dying neutrophils destroyed by macrophages, fibroblasts multiplying & synthesizing collagen, starts tissue repair, may lead to scar tissue formation |
| cardinal signs of inflammation | redness, heat, swelling, pain, and loss of function |
| redness results from... | increased blood flow |
| heat results from... | increased blood flow and increased metabolic activity within the area |
| swelling results from... | increase in fluid loss from capillaries to interstitial space |
| pain results from... | stimulation of pain receptors from compression from interstitial fluid |
| loss of function results from... | may occur in severe cases |
| fever | abnormal elevation of body temperature (at least 1 degree Celsius from normal 37 degrees Celsius), may accompany inflammatory response, requires increased fluid intake to prevent dehydration (due to excess fluid loss) |
| events of fever | onset, stadium, and defervescence |
| onset | period during which temperature begins to rise, hypothalamus stimulating dermis blood vessels to vasoconstrict, may occur with chills and shivering |
| stadium | period when elevated temperature maintained, increased metabolic rate, promotes physiologic processes involved in eliminating harmful substance |
| defervescence | period when temperature returning to normal set point, hypothalamus stimulating mechanisms to release heat (i.e. increased vasodialtion of skin blood vessels, sweating |
| benefits of fever | inhibits reproduction of bacteria and viruses, increases activity of adaptive immunity, accelerates tissue repair, and recommended to leave a low fever untreated |
| risks of high fever | high fevers are potentially dangerous, change in metabolic pathways and denaturation of proteins, possible seizures, irreversible brain damage if over 106 F and death likely if over 109 F |
| adaptive immunity | initiated upon entry of foreign substance, takes longer to respond than innate immunity, contact with antigen (causes lymphocyte to proliferate and form specialized "army"), lymphocytes and products released, considered third line of body's defense |
| immune response | lymphocytes and products released with adaptive immunity |
| two branches of immunity | cell-mediated immunity and humoral immunity |
| cell-mediated immunity | immune response involving T-lymphocytes |
| humoral immunity | immune response involving B-lymphocytes, develop into plasma cells to release antibodies |
| foreign antigens | different in structure from human body's molecules and bind body's immune components |
| self-antigens | body's molecules, typically do not bind immune components |
| immune system is generally able to distinguish between | foreign and self-antigens |
| autoimmune disorder | when the body reacts to self-antigens as if foreign |
| T- and B-lymphocytes | have unique receptor complexes, about 100,000 per cell, each complex binding specific antigen |
| B-lymphocytes | make direct contact with antigen |
| T-lymphocytes | must have antigen processed, antigen presented in plasma membrane of another cell type, and have additional receptor molecules (coreceptors) |
| coreceptors | facilitate T-lymphocyte interaction with cell presenting antigen |
| two types of T-lymphocytes | helper T-lymphocytes and cytotoxic T-lymphocytes |
| Helper T-lymphocytes | help activate B-lymphocytes and other immune cells, contain CD4 in plasma membrane, and classified as CD4 cells and bind to MHC II complex |
| cytotoxic T-lymphocytes | release chemicals toxic to cells, contain CD8 in plasma membrane, classified as CD8 cells that bind to MHC I complex |
| antigen presentation | display of an antigen on a cell's plasma membrane, process performed by other cells (help T-lymphocytes "see" the antigen), and two types of cells presenting antigen to T-lymphocytes |
| two types of cells presenting T-lymphocytes | all nucleated cells of the body and antigen-presenting cells (APCs) |
| antigen-presenting cells | any immune cell communicating antigen presence to T-lymphocytes (dendritic cells, macrophages, and B-lymphocytes |
| antigen presentation | requires physical attachment of antigen to transmembrane protein (termed major histocompatibility complex [MHC] and a group of genes codes for MHC molecules in plasma membrane) |
| two major MHC groups | MHC I and MHC II |
| MHC I | found in all nucleated cells |
| MHC II | found in APCs (in addition to MCH I) |
| three events in life of lymphocytes | formation and maturation, activation of lymphocytes, and effector response |
| formation and maturation of lymphocytes | occurs within primary lymphatic structures (red bone marrow and thymus), become able to recognize one specific foreign antigen |
| activation of lymphocytes | migrate to secondary lymphatic structures, usually where they are first exposed to antigen they bind, and become activated and replicate to form identical lymphocytes |
| effector response | action of T-lymphocytes and B-lymphocytes to eliminate antigen (T-lymphocytes migrate to site of infection and B-lymphocytes remain within secondary lymphatic structures) |
| B-lymphoctyes remaining within secondary lymphatic structures | synthesize and release large quantities of antibodies against antigen, enter blood and lymph and are transported to infection site |
| mechanisms activated lymphocytes use to help eliminate antigen | Helper T-lymphocytes (release IL-2 and other cytokines, regulate cells of adaptive and innate immunity), cytotoxic T-lymphocytes (destroy unhealthy cells by apoptosis), and plasma cells (produce antibodies) |
Created by:
Nicolekr
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