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mct
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The Cardiovascular system (in a nutshell...)
- Circulated blood through tissues
- Delivers important substances to cells
- Removed waste from cells
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Blood
- Mixture of formed elements and plasma
- Plasma: liquid
- -transported dissolved nutrients and waste products
- -transports antibodies
- Formed elements:
- -red blood cells: carry O2 and CO2
- -white blood cells (leukocytes): defend against infection
- -platelets: involved in clotting
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Lymphatic System
- Essential part of blood cirulation
- -plasma filters out of capillaries into interstitial fluid
- Lymph capillaries surround tissue cells
- -larger, more permeable than blood capillaries
- Interstitial fluid is picked up by lymph capillaries in the interstitial space
- Once the plasma (interstitial fluid) enters the lymph capillaries it is called lymph
- Lymph capillaries - very permeable
- -easily pick up microorganisms or their products
- Lymph nodes: contain macrophages, B cells and T cells
- -help clear infectious organisms from lymph
- -sometimes lymph nodes becomes infected and swollen: buboes = infected lymph nodes
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How the bacteria get into blood
- Breach of skin
- -trauma
- Infection and inflammation of tissues
- -perforation/penetration of intestine
- -appendicitis
- -invasion (eg. Salmonella)
- -oral surgery, rift in gums
- -kidney or lung infection
- -catheters
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Bacterial Diseases
- Septic shock
- Puerperal sepsis
- Endocarditis
- -subacute
- -acute
- -pericarditis
- Rheumatic fever
- Plague
- Lyme disease
- Epidemic typhus
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Septic Shock
- Blood is normally sterile
- A few microorganisms are OK
- -defensive phagocytic cells
- -low in iron (iron in RBC): many microorganisms require iron for growth; lysis of RBC, acellerated microbial growth
- Can be caused by Gram negative or Gram positive organisms
- -most severe if Gram negatives are involved
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Septic shock diseases
- septicemia or sepsis: toxic condition resulting from uncontrolled bacterial proliferation in blood due to failure of defenses
- -clinical symptoms: chills, fever, accelerated breathing and heart rate
- -cytokines are released
- -OFTEN FATAL
- Lymphangitis: inflamed lymph vessels
- Severe sepsis: when sepsis results in drop in blood pressure and dysfunction of at least one organ
- -low blood pressure can still be controlled by addition of fluids
- Septic Shock: final stage of sepsis
- -blood pressure can no longer by controlled by addition of fluids
- -multi-organ failure often occurs
- -very high mortality rate
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Gram-negative septic shock
- Gram-negative organisms = most common cause of sepsis
- A.k.a. endotoxic shock
- -due to release of endotoxins (LPS) from G- cell wall
- -less than 1 nanogram is enough LPS to cause symptoms
- ->200,000 fatal cases of septic shock per year in USA
- No effective treatment exists
- -early symptoms are non-specific, therefore may not be diagnosed in time
- -administration of antibiotics at later stages may aggravate symptoms
- -supportive therapy is key
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3 pathogenesis of the Gram negative Septic shock
- Endotoxin - Activation of macrophages
- cytokin release
- fever,
- increased leakage from blood vessels, decreases in blood pressure, SHOCK or decrease OXYGEN EXCHANGE
- or Increase in PMN adhesiveness, PMN traffic to lungs, release of lysosomal contents of PMN, increased capillary leakage, LUNG DAMAGE
- Endotoxin - Complement activation
- PMN traffic to lungs, release of lysosomal contents of PMN, increased capillary leakage, LUNG DAMAGE
- or
- increased leakage from blood vessels, decreases in blood pressure, SHOCK or decrease OXYGEN EXCHANGE
- Endotoxin - Activation of clotting
- DIC
- or tissue damage from clots, then abnormal blood flow, then ORGAN SHUTDOWN
- or decreases in available clotting proteins, HEMORRHAGE
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History - Peurperal Sepsis
- Peurperal fever, childbirth fever
- Nosocomial nfection
- Infection of uterus (often S. pyogenes) -> infection of abdominal cavity (peritonitis) -> septicemia (often)
- Transmitted by hands and instruments of physicians can be treated with penicillin
- -disinfection/modern hygienic practices make this very uncommon
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Dr. Ignaz Semmelweiss
- 1824-1848: peurperal sepsis was cause of death of avg 10% of women who gave birth in a particular clinic in a Vienna hospital
- Compare with avg 4% in a separate clinic in the same hospital
- First clinic: med students, second clinic: midwives
- Alternate admission days; street births
- 1847: death of Kolletschka
- 1847: handwashing with chlorine introdruced
- 1849: Semmelweiss dismissed
- 1865: committed to mental institution, dies 14 days later of septicemia
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Rheumatic Fever
- Follows Groups A streptococcal pharyngitis (S. pyogenes)
- -antibodies against M-protein cross-react between strep antigens and host heart valves (autoimmune)
- Age 4-18 most susceptible (not treated with beta-lactam)
- Sore throat -> short period of arthritis, fever
- -subcutaneous nodules at joints may be present at this stage
- Inflammation of heart in ~50% of cases
- -permanent valve damage
- Glomerulonephritis (due to immune complex formation from anti-streptococcal antibodies)
- Re-infection with Strep: can renew immune attack
- Heart damage may be fatal
- Treatment - monthly penicillin injection
- Sydenham's chorea (Saint Vitus dance) in ~10% of cases
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Endocarditis
- endocardium: epithelial tissue that lines heart muscle and covers valves
- subacute bacterial endocarditis: slow development
- -alpha-hemoplytic streptococci, staphylococci, enterococci
- -fever, general weakness, heart murmur
- -usually starts with focus of infection elsewhere in body: tooth extraction, tonsillectomies can release bacteria; abnormal heart valves increase risk- congenital, rheumatic fever, syphillis; bacteria lodge in blood clots (protected from immune system)
- -fatal within a few months if untreated
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Endocarditis: acute bacterial endocarditis
- Rapid progression
- -Staphylococcus aureus
- -bacteria migrate from focus of infection
- -normal or abnormal valves are affected
- -untreated: fatal within days
- -prophylactic penicillin sometimes used during tonsillectomies and tooth extractions: limited effectiveness
- Pericarditis: infection of sac around heart (pericardium)
- -streptococci
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