Flashcards in Immune system Deck (94)
What is a communicable disease?
Diseases caused by foreign organisms invading the body and multiplying there. They can be transmitted from one person to another.
What is a pathogen?
Disease causing organisms
Contagious communicable diseases
Passed on by direct contact with a person suffering from the disease
spread the disease from person to person trough intermediate hosts of the pathogen, such as mosquitos or fleas
Types of pathogens
- Animal parasites
What are bacteria?
- Many are non-pathogenic and harmless to humans
- Consists of a single cell
- Cell shape is used to clarify bacteria
Examples of bacteria
- Meningitis (bacterial)
- Whooping cough
What are viruses?
- Molecule of DNA or RNA surrounded by a coat of protein
- When a virus infects a living cell, the DNA or RNA induces the cell to manufacture more virus particles
- The new virus particles leave the host cell to infect other cells
What are bacteriophages?
Viruses that multiply in bacterial cells, causing death of the bacterium
Examples of viruses
- Chicken pox
Examples of fungi
- Ring worms
Examples of animal parasites?
- Tape worms
6 ways pathogens can be transmitted?
- Transmissions by contact
- Transfer of body fluids
- Infection by droplets
- Airborne transmission
- Transmission by vectors
Transmission by contact
- Through direct (touching an infected person) or indirect means (toughing an object that has been touched by an infected person)
Transfer of body fluids
- Such as blood, semen, or breast milk
- HIV, hepatitis B and C are spread this way
Infection by droplets
- Emitted when breathing, sneezing or coughing
- Spreads diseases such as measles, mumps, colds and influenza
- Can cause infection when inhaled
Transmission by vectors
- Transfer of pathogens by other animals, such as insects, ticks or mice
What are non-specific defences?
Work against all pathogens
What are specific defences?
Directed at particular pathogens
What is the purpose of the first line of defence?
- Prevents pathogens from entering and multiplying inside the body
- Provides a tough impervious barrier
- Oily secretions called sebum (produced in the oil glands) contain substances that kill some pathogenic bacteria
- Sweat also contains salts and fatty acids that prevent the growth of many micro-organisms
- Line body cavities that open to the exterior
- Secrete mucous which inhibit the entry of micro-organisms to organs of the body
- EG. in the digestive, urinary and reproductive tracts
Hairs and cilia
- EG. nose cavity and ears
- Trap microbes
- The beating of the cilia moves mucous containing trapped particles and micro-organisms towards the throat
- It is then coughed up or swallowed
- Gastric juices and vaginal secretions are acidic
- Inhibit or destroy microbes
- Sweat is slightly acidic
- An enzyme that kills bacteria
- It is in our tears, saliva, sweat and nose secretions
- Our eyes are protected by the flushing actions of our tears, which contains this enzyme
- Traps microbes and debris
- Slightly acidic and contains lysozyme
- Urine flows from the urethra
- Has a cleansing action
- Flushes microbes out of the body
- Prevents bacteria growth and helps to stop bacteria from reaching the bladder and kidneys
- Tears, sweat and saliva are also involved in flushing out microbes
helps to protect the body from injury or infection