Tissue Responses To Injury & Infection Midterm Notes PDF

1 1 TISSUE RESPONSES TO INJURY AND INFECTION – Infec&on Concepts 1. Cause of Infec.on Microbial Invasion: Infec)on occurs when a pathogen (bacteria, virus, fungi, or parasite) enters the body...

1 1 TISSUE RESPONSES TO INJURY AND INFECTION – Infec&on Concepts 1. Cause of Infec.on Microbial Invasion: Infec)on occurs when a pathogen (bacteria, virus, fungi, or parasite) enters the body and evades host defenses. Types of Pathogens: o Bacteria: Cause diseases like tuberculosis, pneumonia, and bacterial meningi)s. o Viruses: Cause diseases like COVID-19, influenza, and herpes. o Fungi: Cause diseases like candidiasis and.nea infec.ons. o Parasites: Cause diseases like malaria and giardiasis. 2. Pathophysiology of Infec.on The pathophysiological process of infec)on involves the following stages: 1. Incuba.on Period: o Defini.on: Time between exposure to the pathogen and the appearance of the first symptoms. o Process: Pathogens enter the host, colonize target )ssues, and begin to mul)ply. o Dura.on: Ranges from a few hours to years (e.g., HIV latency period). 2. Prodromal Stage: o Defini.on: Period of early symptoms that are oNen mild (e.g., malaise, fa)gue). o Pathophysiology: Pathogens mul)ply, releasing toxins and other virulence factors. o Clinical Symptoms: General discomfort, fa)gue, and mild fever. 3. Invasion (Acute Illness) Period: o Defini.on: Rapid mul)plica)on of pathogens and spread to other areas of the body. o Pathophysiology: Tissue damage occurs, and the immune and inflammatory responses are triggered. o Clinical Symptoms: Fever, specific organ-related symptoms (like cough in pneumonia) as the pathogen invades the target )ssue. 4. Convalescence: o Defini.on: Recovery period aNer infec)on, when symptoms resolve. o Pathophysiology: The immune system eliminates pathogens and repairs damaged )ssues. o Outcome: Can result in complete recovery, latency (like HSV-1/HSV-2), or chronic infec)on (like hepa..s C). 3. Transmission of Infec.on Pathogens spread from one host to another using mul)ple mechanisms: 1. Direct Transmission: o Person-to-person contact: Transfer of pathogens through touching, kissing, or sexual contact. o Ver.cal transmission: Mother-to-child transmission, e.g., HIV during childbirth. 2. Indirect Transmission:  2 o Fomite transmission: Pathogens transmiTed through contact with contaminated objects (e.g., door handles, medical equipment). o Airborne transmission: Pathogens like SARS-CoV-2 spread through droplets in the air. o Vector-borne transmission: Pathogens like Plasmodium (malaria) are transmiTed by vectors (like mosquitoes). 3. Waterborne/Foodborne Transmission: o Pathogens like Vibrio cholerae spread via contaminated water or food. 4. Zoono.c Transmission: o Occurs when pathogens jump from animals to humans, as seen with SARS-CoV and Ebola virus. 4. Risk Factors for Infec.on Several factors increase the risk of infec)on: 1. Host Factors: o Age: Newborns and older adults have weaker immune responses. o Immune Status: Immunosuppression from diseases (e.g., HIV, cancer) or drugs (e.g., cor)costeroids) increases suscep)bility. o Comorbidi.es: Condi)ons like diabetes and chronic kidney disease increase suscep)bility. 2. Environmental Factors: o Overcrowding: High popula)on density increases exposure to pathogens. o Poor Hygiene and Sanita.on: Lack of access to clean water and sanita)on increases the risk of waterborne and foodborne diseases. 3. Pathogen-Specific Factors: o Pathogenicity and Virulence: The ability of the pathogen to cause disease. o Immune Evasion: Pathogens like HIV evade immune responses through muta)on and latency. 4. Exposure Factors: o Healthcare exposure: Use of contaminated medical instruments (like needles) and exposure in healthcare se\ngs (healthcare-acquired infec)ons, HAIs). o Travel History: Travel to endemic regions can increase the risk of exposure to novel pathogens (e.g., Ebola in Africa). Summary Table Infec.on Cause Pathophysiology Transmission Risk Factors Concept Bacteria like Invasion, )ssue Direct, fomite, Bacterial Age, immunity, Staphylococcus, E.damage, toxin waterborne, Infec.on comorbidi)es, hygiene coli release zoono)c Viral entry, Viral Viruses like SARS- Airborne, direct, Age, chronic disease, replica)on, immune Infec.on CoV-2, Influenza ver)cal healthcare exposure evasion  3 Infec.on Cause Pathophysiology Transmission Risk Factors Concept Fungal Candida albicans, Kera)n invasion, Direct, fomites, Moist skin, diabetes, Infec.on Dermatophytes immune evasion autoinfec)on immunosuppression Invasion of )ssues Parasi.c Plasmodium Vector-borne, Travel to endemic and organs, immune Infec.on (malaria), Giardia waterborne areas, poor sanita)on evasion Spillover event, Contact with Zoono.c Ebola, SARS-CoV, Travel, animal contact, cross-species animals or Infec.on MERS-CoV healthcare exposure transmission vectors