Study "Cell Biology", a flashcard deck on FORKSAI.
Define 'pathogenicity' and 'virulence' and explain their relationship.
Pathogenicity is the ability of a microbe to cause disease by overcoming host defenses. Virulence is the degree or extent of pathogenicity. Therefore, virulence quantifies how capable a pathogen is at causing disease.
How does the gastrointestinal tract act as a portal of entry for pathogens, and what challenges do microbes face there?
The gastrointestinal tract serves as a portal of entry through contaminated food, water, or fingers. Most microbes entering this route are destroyed by stomach acid and digestive enzymes. However, those that survive can cause diseases like polio, hepatitis A, and typhoid fever.
Explain the concept of a 'preferred portal of entry' for pathogens.
A preferred portal of entry is a specific avenue that a pathogen must use to gain access to the host in order to cause disease. If the pathogen enters the body through a different route, it might not be able to establish an infection or cause illness.
Distinguish between ID50 and LD50, and explain what each measures.
ID50 stands for the infectious dose for 50% of a sample population, measuring the virulence of a microbe by indicating how many microbes are needed to cause infection in half the population. LD50 stands for the lethal dose for 50% of a sample population, measuring the potency of a toxin or pathogen by indicating the amount required to kill half the population.
In what situation would the parenteral route be the primary portal of entry for a pathogen?
The parenteral route would be the primary portal of entry when microorganisms are deposited directly into host tissues, bypassing natural barriers like skin or mucous membranes. This occurs through events such as punctures, injections, bites, cuts, wounds, or surgical procedures.
Why is the respiratory tract considered the 'easiest' portal of entry for microbes?
The respiratory tract is considered the easiest portal of entry because microbes can be readily inhaled into the nose or mouth within drops of moisture. This constant exposure to airborne particles makes it a frequent entry point for many common infectious diseases.
How does the number of invading microbes influence the likelihood of disease?
The likelihood of disease generally increases as the number of invading microbes increases. If only a few microbes enter, they are likely to be overcome by the host's defenses. However, a larger number of pathogens can overwhelm these defenses, making disease more probable.
What are the primary portals of entry for pathogens into the human body?
The primary portals of entry for pathogens into the human body are mucous membranes, the skin, and the parenteral route. Each of these avenues allows microbes to gain access to host tissues and potentially establish an infection.
How do some microbes manage to penetrate unbroken skin, despite its protective function?
While unbroken skin is largely impenetrable, some microbes can gain access through natural openings like hair follicles and sweat gland ducts. Additionally, certain organisms, such as hookworm larvae, can actively bore through intact skin, and some fungi can grow on the keratin in the skin itself.
What types of diseases are commonly transmitted via the genitourinary tract?
The genitourinary tract is the portal of entry for diseases contracted sexually, often referred to as sexually transmitted infections (STIs). Examples include HIV infection, genital warts, chlamydia, human herpesvirus-2, syphilis, and gonorrhea.