Test 5

• Infection- a condition in which pathogenic microbes penetrate host defenses, enter tissues, adn multiply
• 1. contact - microbes adhere to exposed body surface
• 2. colonization with flora
• 3. invasion - microbes cross lines of defense and enter sterile tissue
• 4. infection - pathogenic microbes mulitply in the tissues

• Most areas of the body in contact with the outside enviornment harbor resident microbes; Internal organs, tissues, and fluids are microbe-free
• Transients - microbes that occupy the body for only short periods of time
• Residents - microbes that become established
• Indingenous flora
• Microflora
• Biota
• Commensuals

They occur when normal flora is introduced to a site that was previously sterile

• Uterus and contents are normally sterile and remain so until just before birth
• Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora

• Skin is the largest and most accessible organ
• 2 cutaneous populations. Transients - influences by hygiene and Resident - stable, predicatable, less influenced by hygeine.
• Can also find in GI tract, upper respiratory tract, genital tract, urinary tract, eyes and ears

• Virulence factors - traits used to invade and establish themselves in the host, also determine the degree of tissue damage that occurs, severity of disease. Any characteristic or structure of a microbe that contributes to the disease state.
• Exoenzymes - dissolve extracellular barriers and penetrate through or between cells
• Toxigenicity - capacity to produce toxins at the site of multiplication. 1. Endotoxin - toxin not secreted but is released after the cell is damaged. 2. Exotoxin - toxin molecule secreted by a living bacterial cell into the infected tissue

• 1. Incubation period - time from the initial contact w/ the infectious agent to the appearance of first symptoms; agent is multiplying but damage is insufficent to cause symptoms; several hours to several years
• 2. Prodromal stage - vague feelings of discomfort; nonspecific complaints
• 3. Period of invasion - multiples at high levels, becomes well-established; more specific signs and symptoms
• 4. Convalescent period - as person begins to respond to the infection, symptoms decline

• 1. Localized infection - microbes enter the body and remains confined to a specific tissue
• 2. Secondary infection - another infection by a different microbe
• 3. Mixed infection - several microbes grow simultaneously at the infection site
• 4. Polymicrobial
• 5. Acute infection -comes on rapidly, with severe but short-lived effects
• 6. Systematic infection - infection spreads to several sites and tissue fluids usually in the bloodstream
• 7. Focal infection - when infetious agent breaks loose from a local infection and is carried to other tissues

• Earliest symptoms of disease as a result of the activation of the body defenses. Fever, pain, soreness and swelling
• Signs of inflammation
• Edema - accumulation of fluid
• Granulomas and abscesses - walled-off collections of inflammatory cells and microbes
• Lymphadenitis - swollen lymph nodes

When a disease can be identified or defined by a collection of signs or symptoms

• Edema - accumulation of fluid
• Granulomas and abscesses - walled-off collections of inflammatory cells and microbes
• Lymphadenitis - swollen lymph nodes
• Fever, pain soreness and swelling

• Immunology - the study of body's second and third lines of defense
• Epidemiology - the study of the frequency and distribution of disease and health-related factors in human populations

• World Health Organization
• Specialized agency of the United Nations that acts as a coordinating authority on internationl public health

• Center for Disease Control and Prevention
• A Federal agency in the Dept of Health and Human Services; located in Atlanta -investigates and diagnoses and tries to control or prevent diseases
• (esp new and unusual diseases)

• Incidence - a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period.
• Prevalence - which is a measure of the total number of cases of disease in a population, rather than the rate of occurrence of new cases

• Endemic - disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale
• Sporadic - when occasional cases are reported at irregular intervals
• Epidemic - when prevalence of a disease is increasing beyond what is expected
• Pandemic - epidemic across contients

• Primary habitat of pathogen in the natural world.
• Human or animal carrier, soil, water, plants

• Carrier - an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to the microbe
• Fomite - any inanimate object/substance capable of carrying infectious organisms and hence transferring them from one individual to another. It can be anything from a cloth to a mop head.

• Carrier - an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to microbe
• Vector - A live animal (other then human) that transmits an infectious agent from one host to another

• Aerosol - airborne infectious that are caused indirectly stuff like, TB, Influenza virus, hantavirus
• Mechanical - not necessary to the life cycle of an infectious agent and merely transports it without being infected

• Indirect contact pattern of transmission - passes from infected host to intermediate conveyor and then to another host
• Airborne - droplet of nuclei, aerosols

Biological vectors - actively participate in a pathogen's life cycle

Respiratory tract

• Skin and mucous membranes of respiratory, urogenital, eyes and digestive tracts
• Outermost layer of skin is composed of epithelial cells compacted, cemented together and impregnated w/ keratin; few pathogens can penetrate if intact
• Flushing effect of sweat glands
• Damaged cells are rapidly replaced
• Mucous coat impedes attachment and entry of bacteria
• Blinking and tear production
• Stomach acid
• Nasal hair traps larger particles

• First line of defense - any barrier that blocks invasion at the portal of entry - nonspecific
• Second line of defense - protective cells and fluids; inflammation and phagocytosis - nonspecific

• Neutrophils - 55-90% - lobed nuclei w/ lavender granules; phagocytes
• Eosinophils - 1-3% - orange granules and bilobed nucleus; destroy eukaryotic pathogens
• Basophils - 0.5% - constricted nuclei, dark blue granules; release potent chemical mediators. Mast Cells: nonmotile elements bound to connective tissue
• Lymphocytes - 20-35% - specific immunte response. B humoral immunity - activated B cells produce antibodies. T Cells - Activated T cells modulate immune functions and kill foreign cells.
• Monocytes, macrophages - 3-7% - largest of WBC's, kidneyshaped nucleus; phagocytic

• Diapedesis - migration of cells out of blood vessels into the tissues
• Hemopoiesis - production of blood cells

.92% water, metabolic proteisn, globulins, clotting factors, hormones, and all other chemicals and gases to support normal physiological functions

• Reticuloendothelial System: network of connective tissue fibers that interconnects other cells and meshes with the connective tissue network surrounding organs.
• Inhabited by phagocytic cells - mononuclear phagocyte system - maacrophages ready to attack and ingest microbes that passed the first line of defense

• Spleen - structurally similar to lymph node; filters circulating blood to remove worn out RBC's and pathogens
• Thymus - high rate of growth and activity until puberty, then begins to shrink; site of T-cell maturation
• Lymph nodes - small, encapsulated, bean-shaped organs stationed along lymphatic channels and large blood vessels of the thoracic and abdominal cavities
• Misc - GALT, Peyers patch

• Classic signs and symptoms characterized by:
• Redness - increased circulation and vaso dilation in injured tissues in response to chemical mediators and cytokines
• Warmth - heat given off by the increased blood flow
• Swelling - increased fluid escaping into the tissue as blood vessels dilate - edema; WBC's microbes, debris and fluid collecting to form pus; helping prevent spread of infection
• Pain - stimulation of nerve endings
• Possible loss of function

• Initiated by circulating pyrogens which reset the hypothalamus to increase body temperature; signals muscles to increase heat production and vasoconstriction.
• Exogenous pyrogens - products of infectious agents
• Endogenous pyrogens - liberated by monocytes, neutrophils, and marcophages during phagocytosis; interleukin-1 (IL-1) and tumor necrosis factor TNF
• Benefits of fever:
• Inhibits multiplication of temperature - sensitive microorganisms
• Impedes nutrition of bacteria by reducing the available iron
• Increases metabolism and stimulates immune reactions and protective physiological processes

Third line of defense - acquired w/ exposure to foreign substance; produces protective antibodies creates memory cells - specific