Immune system Flashcards
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
Vectors
spread the disease from person to person trough intermediate hosts of the pathogen, such as mosquitos or fleas
Types of pathogens
- Bacteria
- Viruses
- Fungi
- 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
- Chlamydia
- Meningitis (bacterial)
- Tetanus
- 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
- HIV/AIDS
- Chicken pox
- Colds
Examples of fungi
- Ring worms
- Thrush
- Tinea
Examples of animal parasites?
- Tape worms
- Thrush
- Ticks
6 ways pathogens can be transmitted?
- Transmissions by contact
- Transfer of body fluids
- Infection by droplets
- Ingestion
- 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
Airborne transmission
- 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
The skin
- 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
Mucous membranes
- 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
Acids
- Gastric juices and vaginal secretions are acidic
- Inhibit or destroy microbes
- Sweat is slightly acidic
Lysozyme
- 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
Cerumen
- Traps microbes and debris
- Slightly acidic and contains lysozyme
Flushing action
- 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
Protective reflexes
helps to protect the body from injury or infection
- Sneezing
- Coughing
- Vomiting
- Diarrhoea
Second line of defence
Non-specific and occurs if a pathogen gets past our external defences
The immune system consists of:
- The lymph nodes
- Lymph vessels
- Lymphoid tissues (scattered throughout organs)
- Many different leucocytes circulating throughout the body
Where does the lymphatic system drain fluid?
Drains intercellular fluid back to the heart at the vena cava
What are phagocytes?
Cells that can engulf and digest micro-organisms and cell debris
What are leucocytes?
- White blood cells
- Able to leave blood capillaries and migrate through the tissues to places of infection or injury
Types of non-specific immunity?
- Inflammatory response
- Phagocytosis
- Fever
What is the inflammatory response?
The response to an damage to the tissues
Purpose of the inflammatory response?
- Reduce the spread of pathogens
- Remove damaged tissues and cell debris
- Begin repair of the damaged tissues