First line of defence Flashcards
What are communicable diseases caused by and how are they transmitted
Caused by micro-organisms, usually bacteria, viruses, fungi, protozoa, transmitted from one person to another
What is a pathogen
Disease-causing organism
Non-specific/generalised defence
Response to all infection or injuries
Specific defence
Works against selected pathogens
Bacteria
A single cell organism that may or may not be pathogenic
Types of bacteria
Cocci, Bacilli, Spirilla, Vibrio
Diseases caused by bacteria
Valley fever, Rat-bite fever, Vibriosis and cholera
Virus
An infectious agent consisting of a protein coat surrounding a core of nucleic acid
Bacteriophage
A virus that infects bacteria
Examples of viruses
Monkeypox, COVID, Chickenpox
6 ways pathogens can be transferred
Contact, bodily fluids, droplets, contaminated food/drink, airborne transmission, by vectors
Transmission by contact through indirect or direct means
Involves the spread of pathogens by touching an infected person of an object they have touched, E.g- STI’s such as chlamydia
Transfer of bodily fluids
When blood or other body fluids (saliva, mucus) from an infected person comes into contact with mucus membranes (nose, mouth) or the bloodstream of an uninfected person, E.g- HIV, Hep B and C
Infection by droplets
When tiny droplets of moisture that have pathogens in them are breathed in by uninfected people (still has moisture), E.g- COVID, Flu
Ingestion of contaminated food or drink
Food or drink contaminated with pathogens is ingested, E.g- Salmonella
Airborne transmission
When moisture in exhaled droplets evaporates, some pathogens remain and can be inhaled (no moisture left), E.g- Cold
Transmission by vectors
The transfer of pathogens by other animals such as insects, E.g- Malaria, Rabies
3 lines of defence
Keep microbes out of body, Non-specific attack on microbes, Specific attack on microbes
What is the first line of defence
Prevents entry and reproduction of pathogens in the body
What structures prevent the entry of pathogens
External defences and protective reflexes
Why isn’t the first line of defence always successful
Burns and cuts to the skin reduce the effectiveness of the first line of defence
Chemical external defences (4)
Cerumen, acids, lysozyme, skin
Cerumen
Ear wax, slightly acidic, contains lysozyme that kills bacteria
Acids
Acid kill bacteria
Lysozyme
Enzyme that kills bacteria
Skin as a chemical defence
Sebum kills bacteria, Sweat contains salts and fatty acids and prevents growth of micro-organisms
Mechanical external defences (4)
Mucous membranes, hairs, flushing action, skin
Mucous membranes
Secretes mucus that traps particles, Inhibit micro-organisms from entering
Hairs
Hair and layer of mucus traps up to 90% of particles
Flushing action
Flushing of body fluids helps to keep some areas relatively free from pathogens
Skin as a mechanical defence
Barrier
4 protective reflexes
Sneezing, coughing, vomiting, diarrhoea
Sneezing
Caused by irritation on the walls of the nasal cavity by noxious fume or dust that carries micro-organisms, Forceful expulsion of air carries mucus, foreign particles and irritating gases out
Coughing
Irritation in the lower respiratory tract (bronchi and bronchioles), Air forced from lungs moves irritant out and up the trachea
Vomiting
Caused by psychological stimuli, excessive stretching and bacterial toxins, Contraction of abdomen muscles and diaphragm expels stomach contents
Diarrhoea
Caused by irritation of small and large intestine by bacteria, viruses or protozoa’s, Irritation causes increased contractions of the muscles in the wall of intestine meaning material doesn’t stay in the large intestine to absorb enough water
