Immune System Flashcards
Pathogen
Disease-causing agent
What is the main function of the immune system and what are the 3 ways in which this is achieved?
To protect the body against infection
- Prevent entry of pathogens (1st line, innate)
- Trap and destroy any pathogens (2nd line, innate)
- Destroy specific pathogens (3rd line, adaptive)
Describe 4 characteristics of non-specific/innate immunity
- Same response and level of response for all pathogens
- No memory of previous infections
- Immediate response
- 1st and 2nd line of defence
Describe 5 characteristics of specific/adaptive immunity
- Different response and level of response for all pathogens
- Memory of previous infections
- Response to a new pathogen is delayed the first time and faster the second time
- Uses antibodies
- 3rd line of defence
Describe how the 3 components of the first line of defence protect the body from infection
- Physical barriers: physical structures which prevent entry of pathogens
- Chemical barriers: secreted chemicals which prevent entry of pathogens or destroy pathogens which have entered the body
- Microbiological barrier: presence of natural bacteria (e.g. skin, stomach, vagina) prevent colonisation of pathogenic bacteria due to lack of space and resources
State 5 physical barriers
Intact skin, hairs, ear wax, mucociliary escalator, mucous membranes
Describe 3 ways in which the integumentary system acts as a physical barrier
- Intact skin prevents entry of pathogens, keratin in epidermis makes it waterproof
- Dead cells constantly fall off, removing bacteria
- Hair in nose and other places prevents pathogens from entering respiratory/genitourinary tract
Explain the role of the cardiovascular system in ensuring the skin barrier remains intact
Blood clot formation
1. Blood vessel gets damaged and leaks
2. Vasoconstriction reduces blood flow to the area to prevent blood loss
3. Platelets activate and stick to each other, forming a platelet plug to stop bleeding
4. Coagulation: fibrinogen is converted to fibrin which strengthens clot by trapping platelets and erythrocytes
Explain how ear wax acts as a physical barrier
Ear wax traps pathogens, preventing them from entering into the ears
Explain how the mucociliary escalator acts as a physical barrier
Cilia (hair-like projections) on the walls of the bronchi works together with mucus to trap pathogens and sweep them out of the respiratory system
Explain how mucous membranes act as a physical barrier, including where they are found
They produce mucus which traps pathogens and prevent them from further entering into the respiratory, alimentary and genitourinary tracts
State 5 chemical barriers
Saliva, tears, sweat, sebum, HCl in stomach
Explain how saliva, tears and HCl act as a chemical barrier
- Tears & saliva contain lysozymes which break down bacteria
- HCl in stomach has a low pH which destroys pathogens
Explain how sebum and sweat act as a chemical barrier
- Sebum has bactericidal and fungicidal properties
- Sweat contains salt, providing a hostile environment for bacteria
Identify the two lines of defence that prevent infection when someone falls off their bike and grazes their knee
2nd and 3rd
- NOT 1st because they grazed their knee> 1st is already penetrated
State 3 processes that form part of the 2nd line of defence
Inflammation, phagocytosis, fever (lower priority)
What is phagocytosis and why does it occur?
- When WBC recognise, engulf and destroy pathogens or foreign particles
- To fight infection and protect the body from disease
Describe the process of phagocytosis
- Phagocyte recognises pathogen as non-self
- Phagocyte engulfs pathogen, forming a phagosome (vesicle around pathogen)
- Phagosome fuses with lysosome which contains digestive enzymes to break down the pathogen, forming a phagolysosome
- After the pathogen is destroyed, unwanted debris is removed from the cell
Role of neutrophils
First responder to an infection; recognise, engulf and destroy bacteria through phagocytosis
Role of macrophages
- NON-SPECIFIC immune response: recognise, engulf and destroy pathogens through phagocytosis and recruit other immune cells to help fight off an infection
- SPECIFIC immune response: present antigens from pathogens to T-helper cells to initiate a specific immune response
Role of dendritic cells
- Recognise, engulf and destroy pathogens through phagocytosis
- Present antigens from pathogens to Th cells to initiate a specific immune response
How does a fever contribute to the second line of defence?
Increased temperature creates a hostile environment for pathogens, making it hard for them to survive and infect cells
What is inflammation and why does it occur?
- Acute response to tissue damage, causing heat, redness, swelling, pain
- Occurs to protect, isolate and inactivate the cause of damaged tissue e.g. heat extremes, caustic chemicals, trauma, cuts/scratches
Signs vs symptoms of inflammation
- Signs (what you see): swelling and redness
- Symptoms (what you feel): heat and pain
