4.1 - Communicable Diseases - New Flashcards
Pathogen def
A microorganism that causes disease
4 different types of pathogen
Bacteria
Fungi
Viris
Protoctista
Different bacterial diseases
TB
Bacterial Meningitis
Ring Rot (in plants)
Different diseases caused by viruses
HIV/AIDS
Influenza
Tobbaco Mosaic Virus
Different fungal diseases
Black Sigatoka
Ringworm (cattle)
Athlete’s foot (humans)
Diseases caused by protoctista
Blight (tomatoes and potatoes)
Malaria
Direct Transmission def
Passing a pathogen from host to new host, with no intermediary
Indirect Transmission
Passing a pathogen from host to new host, via a vector
Transmission def
Passing a pthogen from an infected individual, to an uninfected individual
Vector def
An organism that carries a pathogen from one host to another
Simple pathogen life cycle
Travel from one host to another (transmission) Enter host tissues Reproduce in host tissues Leave the host tissues Infect a new uninfected person
Different means of direct transmission
Direct physical contact
Faecal-oral transmission
Droplet infection
Transmission by spores
Methods to decrease transmission by direct physical contact
Direct physical contact
- hygiene - wash hands regularly
- keep surfaces clean - especially door handles
- clean and disinfect cuts and abrasions
- sterilise surgical instruments
- use condoms during sexual intercourse
Methods to decrease transmission by faecal-oral transmission
- treatment of waste water and drinking water to decontaminate and reduce risk
- thorough washing of all fresh food (using treated water)
- careful prep and cooking of all food
Methods Methods to decrease transmission by droplet infection
Catch it - bin it - kill it
Cover mouth when coughimg or sneezing
Use tissue and dispose of correctly after use
Methods to decrease transmission by transmission by spores
Use of a face mask
Washing skin after contact with soil
Social factors affecting transmission of diseases
Overcrowding Poor ventilation Poor health - especially with HIV/AIDS Homelessness Living or working with people who ahve migrated from areas where disease is common
Life cycle of Plasmodium and malaria
Person with malaria Gametes of Plasmodium in blood Female Anopheles mosquito sucks blood Plasmodium develops and migrates to mosquito’s salivary glands Uninfected person is bitten Plasmodium migrates to liver Plasmodium migrates to blood
What conditions are optimal for many pathogens
Warm, moist conditions
- allows them to reproduce more rapidly
- so greater variety of pathogens may be present in these conditions
Callose def
A large polysaccharide deposit that blocks old phloem sieve tubes
Plant physical defences, and more info on the,
- Cellulose cell wall - contains many chemical defences that can be activated on detecting pathogen
- Lignin thickening of cell walls - waterproof and almost completely indigestible
- Waxy cuticles - prevent water colection on cell surfaces, prevents pathogens accumulating there, need water to survive
- Bark - contains a variety of chemical defences against pathogens
- Stomatal closure - closed, as are possible points of entry for pathogens - controlled by guard cells when pathigens detected.
- Callose - large polysaccharide deposited in sieve tube at end of growing season.
- blocks flow of assimlates, and pathogens in sieve tube elements
- Tylose Formation - balloon-like swelling or projection that fills the xylem vessel
- plugs vessel, and water (and pathogens) can longer move through the xylem
Chemical defences for plants
Terpenoids Phenols Alkaloids Defensive proteins Hydrolytic enzymes
Active defences in plants, and more info
- Cell walls become thickened with additional cellulose
- Deposition of callose between plant cell wall and memebrabe near invading pathogen
- Oxidative bursts - produce highly reactive O2 molecules capable of damaging invading pathogen cells
- Increase in production of chemicals
- Canker - necrotic lesionin woody tissue - causes death of cambium tissue in bark
Inflammation def
swelling (odoema) and redness caused by infection
what is a mucous membrane?
specialiswd epithelial tissue covered by mucus
primary defences def
defences that prevent pahogens entering the body
list different primary defences in the human body
skin blood clotting and skin repair mucous membranes coughing and sneezing inflammation
Other:
enzymes and antibodies in tear fluid
ear canal lined by wax - traps pathogens
mucus plug in cervix, relatively acidic conditions in vagina
what are the primary “non-specific” defences
defences that prevent pathogens entering the body and bloodstream, but are not specific to any one pathogen or antigen - prevent entry of any pathogen
how does skin act as primary defence
skin conists of layers of cells
outer layer called epidermis
acts as a barrier for pathogens
Outline the process of blood clotting and skin repair
Blood Clotting
platelets bind to exposed collagen
they release clotting factors
this activates an enzyme cascade
this causes fibrinogens to form insoluble fibres that attach to the platelets in the plug
red blood cells and platelets are trapped in place
this forms a blood clot
Skin Repair
when clot has formed
dries out and forms a scab
as it dries, it draws sides of the cut together
makes temp. seal under which skin is repaired
fibrous collagen deposited under scab
stem cells in epidermis divide by mitosis to form new skin cells
they migrate to edge of cut - diff. to form new skin
new blood vessels grow to supply O2 and nutrients to new cells
edge of cut contracts and skin is repaired - scab falls off
how does mucous membrane act as primary defence
thin layers in body, e.g. alveoli, lungs, blood vessels etc., contain mucous membranes
mucus secreted by goblet cells
mucus traps any pathogens
epithelium also contains ciliated cells
cilia can move to waft the mucus with pathogens along and out of airways
enter oesophagus and is swallowed
killed by stomach acid
how coughing and sneezing acts as primary defence
expulsive reflex
expels any pathogens in airway that caused the irritation
inflammation mechanism
pathogen detected by mast cells
this causes release of histamines
causes vasodilation
makes capillary walls more permeable to white blood cells
plasma and WBC leave blood vessel and enter tissue fluid
causes increased prod. of tissue fluid
causes swelling (odoema)
excess tissue fluid drained into lymphatic system - where lymphocytes are stored
can lead to pathogens coming into contact with lymphocytes
causes initiation of primary immune response
what is an antigen presenting cell (APC)?
a cell (usually phagocyte) that incorporates the antigens of a pathogen into its cell surface membrane so it can be recognised by other cells in immune system
clonal selection def
selection of a specific B or T cell specific to the antigen
what are cytokines?
hormone-like molecules used in cell signalling to stimulate the immune response
what are neutrophils?
a type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome),
which fuses with lysosomes to digest the foreign matter.
- a type of phagocyte
what are opsonins?
proteins that bind to the antigen on a pathogen and then allow phagocytes to b
parasite def
an organism that:
- lives in/on host
- gains nutrition from host
- at expense of host
