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Flashcards in Communicable diseases Deck (50):

what is a pathogen?

a microorganism that causes disease


why is a host body good for a pathogen

a host body creates a good environment for the pathogen to live in as it can live of the nutrients caused by the cells


what does the pathogen do to the host body

causes damage to the cells and takes nurients from the host


what kingdom does bacteria belong to



How does bacteria harm the body

they damage cells and release toxins and waste substances that are harmful to the host
- in plants they live in the vascular tissue


where does fungi live

fungi lives in the skin of an animal where its hyphae, this forms a mycelium which grows under the skins surface
- in plants it lives in the vascular tissue where it gains nutrients


how does fungus cause irritation and redness

it sends out special reproductive hyphae which grows on the surface of the skin to release spores this causes the redness and irritation


in plants what does the hyphae do

it releases extracellular enzymes such as cellulases which digest the surrounding tissue and cause decay


what are the symptoms of fungi in plants

- leaves - mottled in colour, curl up, shrivel and die
- fruit - turn black and decay


what doe viruses do inside the cell

they invade the cell and take over the genetic machinery and other organelles of the cell
cell then manufactures more copies of the virus
host cell then bursts and new viruses invade other cells


what do protoctista do?

they enter host cells and feed on the content as they grow


what are the 4 types of pathogen

fungi, bacteria, protoctista, viruses



- bacteria
- affects many parts but kills cells and tissues, lungs are most affected


bacterial meningitis

- bacteria
- infection of the meninges, membranes that surround the brain and spinal cord, the membrane swell and cause damage to the brain and nerves


ring rot

- bacteria
- ring of decay in vascular tissue of a potato tuber or tomato accompanied by leaf wilting



- virus
- attacks cells in the immune system and compromises immune response



- virus
- attacks respiratory system and causes muscle pains and headaches


tobacco mosaic virus

- virus
- causes mottling and discolouration of leaves


black sigatoka (banana)

- fungi
- causes leaf spots in banana a plants reducing yield


blight (tomato and potatoes)

- protoctistan
- affect both the leaves and potato tubers


ringworm (cattle)

- fungus
- growth of fungus in skin with spore cases erupting through skin to cause a rash


athletes foot

- fungus
- growth under skin of feet particularly between the toes



- protoctistan
- parasite in the blood that causes a headache and fever and may progress into coma and death


what is the lifecycle of a pathogen

travel from one host to another
enter hosts tissues
leave hosts tissues


What are the factors effecting direct physical contact

keeping surfaces clean
cleaning and disinfecting cuts
sterilising surgical equipment
using condoms


What are the factors effecting faecal (oral) transmission

using sewage to treat crops
treatment of waste and water
washing all fresh food and careful preparation


what are the factors affecting droplet infection

catch it - bin it - kill it
cover mouth when coughing or sneezing
use a tissue


what are the factors affecting transmission by spores

use a mask
washing skin after contact with soil


what are the means of direct transmission

direct physical contact
- touching an infected person or contaminated surface that harbours the pathogens - HIV, ringworm, athletes foot
- usually by eating or drinking contaminated substances - cholera or food poisoning
droplet infection
- in which the pathogen is carried in tiny droplets in the air, TB, influenza
- a resistant stage of the pathogen carried in air or residue on surface or in the soil - anthrax and tetanus


what other things cause disease

poor ventilation
poor health
poor diet
living and working with people who have migrated from diseased areas


what is a vector used for

its used by the pathogen to gain entry to the primary host


describe the malaria cycle

1. gametes of plasmodium in blood
2, female anopheles mosquito sucks blood
3. plasmodium develops and migrates to mosquitos salivary gland
4. uninfected person is bitten
5. plasmodium migrates to liver
6. plasmodium migrates to blood
7. person with malaria


how do plants have diseases transmitted to them

enter the roots
many fungi produce spores due to sexual and asexual reproduction - these are carried by the wind
enter fruit and seeds and will distribute with the seeds so offspring are infected
pathogens in the leaves when the leaves are shed carry the pathogen back to the soil where it can grow and infect another plant


what does a pathogen do in a plant

effects all vascular tissue,


what effect does climate have on disease

warm and moist conditions increase growth of bacteria, fungi, protoctista
this provides a greater variety of diseases in warmer countries


What is a primary defence?

a primary defence are the mechanisms which evolve to prevent entry of pathogenic organisms from entering the body, for example the skin


Why are primary defences non-specific?

they are non-specific as they have to prevent entry into the body from the various types of pathogens


What is the main primary defence?



Describe the outer layer of skin

the outer layer is called the epidermis and consists of layers of cells called keratinocytes


describe the process of keratinisation

the cells are produced by mitosis at the base of the epidermis they then migrate to the skin surface and dry out, the cytoplasm is replaced by keratein and takes 80 days when they reach the skin surface they are dead, this acts as a barrier


What does blood clotting do?

temporary skill to precvent infection and repair the skin


describe how a clot forms

1. Damaged blood vessels expose collagen and releases clotting factors as connective tissue is now exposed
platelets bind to collagen releasing clotting factors this causes a temporary platelet plug clot
2. The platelets binding to the collagen causes the inactive thrombokinase in the blood to change shape and form an active site so the thrombokinase becomes active
3. The active throbokinase plus calcium ions causes the prothrombin in the blood to turn into active thrombin, this active thrombin turns soluble fibrogen into an insoluble fibrin
4. the fibres attach to platelets in plug and a blood clot forms this traps the red blood cells and platelets


What happens after a clot has formed

the clot begins to dry and form a scab
the scab then shrinks as it drys and draws the sides of the cut together sealing the skin
1. the first stage is the deposition of fibrous collagen under the scab
2. the stem cells then divide by mitosis to form new cells these migrate to the edges of the cut and differentiate to form new skin
3. new blood vessels then grow to supply oxygen and nurtients to the tissues
4. the scab is then released


Why is where the food enters more at risk

where food enters the blood the exchange surfaces are quite thin and less well protected so are more at risk


What produced mucus

goblet cells in the epithelial layer


Where is the mucus/ciliated epithelium

genital areas


How does mucus trap the pathogens

traps pathogens that are in the air, the mucus is then wafted along the trachea by cilia cells where it enters the oesophagus this is swallowed and digested by the pathogen and then killed by the acidity of the stomach


what is an expulsive reflex

coughing or sneezing as a response to irritation, it is caused by the presence of pathogens


what are the other primary defences

eyes produce antibodies and enzymes and tissue fluid
ear wax traps pathogens
female reproductive system has mucus plug in cervix and acidic conditions


How does inflammation work

1. presence of pathogens detected by specialised cells called mast cells
2. mast cells release signalling substance called histamine this causes vascodilation around the infected area and increases the blood flow bringing more phagocytes to the area
3. vascodilation causes the redness, it also increases the size of the pores within the capillary wall this allows the phagocytes to change shape and squeeze out into the tissue fluid
4. the excess tissue fluid is then drained into the lymphatic system where the lymphocytes are stored
5. the pathogen come into contact with the lymphocytes and a specific immune response is started
6. the swelling is caused by an increase in tissue fluid