Biomedical

• Miasma Theory


  Diseases are caused by the foul smells created by decomposing bodies, food and general filth
• Disease associated with poor sanitation, sanitary improvements reduced diseases
• Humoral Theory


  Human body contains four humors: black bile, yellow bile, red bile and phlegm. Imbalance of humors causes disease (dyscrasia), balance of humors causes health (eucrasia)
• Humoral theory is consistent with importance of homeostasis in modern medicine
• John Snow


  • Father of Epidemiology
  • Identified the source of a cholera epidemic in London as a specific public water pump
  • Proposed the concept of "materies morbi" in the water, changed the whole water and waste system
• Louis Pasteur


  • Disproved the doctrine of spontaneous generation
  • Supported the Germ Theory and its application in clinical medicine
  • Developed a powerful vaccine against rabies
  • Invented the technique of pasteurization
• Robert Koch


  • Discovered that the fatal disease anthrax was caused by the Bacillus anthracis
  • First clear link between a specific microorganism (germ) with a specific disease
  • First photography of a bacterium
  • Discovered that the spores of anthrax bacteria could remain dormant or activate
• Koch's Postulates


  Principles of the Germ Theory - specific microorganisms (germs) are responsible for causing specific diseases.
• Koch's Postulates


  • The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms
  • The microorganism must be isolated from a diseased organism and grown in pure culture
  • The cultured microorganism should cause disease when introduced into a healthy organism
  • The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent
• There are some exceptions and corrections to the 4 postulates. 1. Koch discovered asymptomatic carriers of cholera and of typhoid fever. 2. Some pathogens can’t be grown in pure culture and need host (viruses). 3. Some individuals may avoid infection due to a strong immune system, or previously acquired immunity through exposure, vaccination or genetic immunity. 4. Some pathogens can cause different diseases (varicella zoster virus causes chickenpox and shingles), as well as the same disease can be caused by a variety of pathogens (meningitis)
• Types of pathogens


  • Bacteria
  • Viruses
  • Fungi
  • Parasites
• Bacteria


  • Found everywhere (soil, water, air intestines), prokaryotic (they lack a nucleus), reproduce quickly (thought binary fission), not all cause diseases, can cause a wide range of illnesses (tuberculosis, strep throat, food poisoning - salmonella), antibiotics are used to treat bacterial infections (but antibiotic resistance is a growing concern)
• Viruses


  • Can only live inside a host, made of genetic material surrounded by a protein coat, sometimes have an outer lipid envelope, example of diseases - common cold, influenza, HIV/AIDS, COVID-19, vaccines and antiviral drugs are used to treat and prevent viral infections

  
• Fungi


  • Include yeasts, molds and mushrooms, most are not harmful to humans, eukaryotic (they have a true nucleus), reproduce sexually or asexually, example of diseases- athlete’s foot, thrush (candida), cryptococcal meningitis, fungal infections are treated with antifungal medications (also here, the increasing resistance is concerning for public health)
• Parasites


  • They live on or inside a host organism and benefit at the host's expense, vary in size and structure: smaller (Protozoa) or larger (worms), example of diseases: malaria, giardiasis, tapeworm infections, parasitic infections are a major concern in many parts of the world, prevention focuses on sanitation, clean water and vector control
• Main components of the immune system

  • Leukocytes (white blood cells)
  • Antibodies
  • Lymphatic system
  • Bone marrow
  • Thymus
  • Spleen
• Innate Immunity


  Body's immediate, non-specific response to invading pathogens, physical barriers (skin and mucous), immune cells that attack invaders in generalized way.
• Adaptive Immunity


  Activation of specialized cells that recognize, remember and target specific pathogens
• Lifestyle factors that influence the immune system

  • Nutrition
  • Sleep
  • Stress
  • Exercise
• Transmission modes of diseases


  • Contact - direct or indirect contact through surface
  • Droplet - respiratory droplets during coughing or sneezing
  • Airborne - smaller droplets over long distance and times
  • Vector-borne - throught insect like mosquitoes which serve as carriers.
  • Common vehicle - contaminated food, water or medication
• Infection control strategies


  • Vaccinations
  • Antiseptics and disinfectants
  • Antibiotics and antivirals
  • Safe food handling
• Role of nutrition


  • Micronutrients support immune functions, amino acids are necessary for synthesizing antibodies, fibers, prebiotics and phytonutrients shape the microbiota
• Food safety principles


  • Clean - personal hygiene, surface sanitation, food washing
  • Separate - avoid cross-contamination, storage
  • Cook - safe temperature, keep hot foods hot
  • Chill - refrigerate promptly, thaw safely, keep cold foods cold
• By adhering food safety principles, we reduce the risk of foodborne diseases
• How does our body defend itself from these pathogens?


  Recognition, response, memory, adaptability, balance
• Monocytes - large type, involved in chronic infections, they mature into macrophages and dentritic cells.
• lymphocytes - B-cells: produce antibodies for specific invaders. T-cells destroy infected or cancerous cells
• basophils - rarest type, they release histamine and other chemical that control immune response
• eosinophils - role in allergic reaction and asthma
• neutrophils - most abundant, first responders
• antibody - a protein produced by white blood cells that binds to antigens
• lymphatic system - a network of vessels and nodes that circulates lymph fluid and transports immune cells through body
• bone marrow - the soft, spongy tissue found inside bones that produce white blood cells ( so the immune cells) and other cloud cells such as red blood ones and platelets
• thymus - an organ where T-cells mature, becoming ready to fight off pathogens.
• spleen - filters the blood, removing old blood cells and pathogens, and is an important site for immune cell interactions
• lymphocytes - a type of white blood cell involved in adaptive immunity