Primary defences against disease 4.1.4 Flashcards
Why can many pathogens not cause disease?
Due to non specific barriers (physical, chemical) and cellular defences that prevent them from entering
What happens if pathogens do enter the body?
The specific immune response prevents them from spreading through the body
What line of defence is the skin?
1st
Name 3 ways of how skin prevents pathogens from entering the body
- Composed of dead cells containing keratin, which cannot be digested easily = protective barrier to pathogens
- Sebum (sebaceous glands) contain long fatty acid chains - lowers pH and inhibits growth of microorganisms and viruses
- Sweat glands - contain lysozyme which digests cell wall of bacteria
How does sebum prevent the entrance of pathogens?
Sebum contains long fatty acid chains which lowers pH and inhibits the growth of microorganisms and viruses
How does sweat prevent the entrance of pathogens?
Contains lysozyme which digests the cell wall of bacteria
How does keratin in the skin prevent the entrance of pathogens?
It cannot be digested easily and therefore provides a protective barrier to pathogens
Where are mucous membranes found?
They line the gut, airways, and reproductive system
What does the mucous membrane consist of?
Epithelial cells and mucus-secreting cells like goblet cells
What makes mucus sticky?
Many glycoproteins with long carbohydrate chains
What is the function of mucus/mucous membranes?
Mucus in the airways can trap particles such as viruses, bacteria, pollen, and dust
Where are the ‘air’ particles moved too after being trapped in mucus?
They are moved towards the back of the throat by cilia (small, hair like cells)
Name 3 ways the gut defends against pathogens
- HCL acid in stomach - destroys ingested bacteria
- Saliva - lysozyme and amylase
- Gut flora - microorganisms that have a mutualistic relationship with pathogens
How does HCL acid defend against pathogens?
It destroys ingested bacteria
How does saliva defend against pathogens?
It contains lysozymes and amylase
How does gut flora defend against pathogens
They are microorganisms found in the gut which have a mutualistic relationship with pathogens
What defences does the urinary/reproductive tract have?
- Semen - spermine is antibacterial
- Vagina - mucus membrane has lactic acid
- Urethra - acidic due to urine
How does semen defend against pathogens?
It contains spermine which is antibacterial
How does the vagina defend against pathogens?
It has a mucus membrane which has lactic acid
How does the urethra defend against pathogens?
It is acidic due to urine
What are expulsive reflexes?
Coughing and sneezing, which expel foreign objects and happen automatically
How does the nose defend against pathogens?
- Full of hairs and mucus which trap microbes
- Mucus contains lysozymes which break down bacterial and fungal cell walls
- Also contains phagocytes (WBC’s)
How does the eye defend against pathogens?
- Protected by tears and rapid eye movement
- Tears contain water, salts, and lysozymes which destroy bacterial cell walls, and microbes usually die in salty conditions
What do lysozymes do?
Destroy bacterial and fungal cell walls, by digesting things
How does the ear defend against pathogens?
It has yellow sticky ear wax which traps pathogens
How does cilia defend against pathogens?
- Mucus traps microbes and ciliated epithelial cells waft it to the back of your throat, then it is swallowed.
How does the bladder defend against pathogens?
Urine contains lysozymes!
How does the anus defend against pathogens?
- Most microbes are ejected from the anus, and good bacteria out compete the bad bacteria.
What are non specific barriers?
They try to destroy any invading pathogen
At what temperature do pathogens reproduce best at?
At or below 37°C
When does the specific immune system work faster?
At higher temperatures
How is normal body temperature maintained?
By the hypothalamus in the brain
What happens in the brain when a pathogen invades the body?
Cytokines stimulate your hypothalamus to reset the thermostat and your temperature goes up.
What are the steps of the cascade mechanism (blood clotting)?
- Damaged walls and platelets release, thromboplastin, Ca2+, and vitamin K
- These combine with prothombin to form the enzyme thrombin
- Thrombin catalyses the reaction from fibrinogen (which is soluble) to fibrin (which is insoluble)
- A clot is formed
How does inflammation occur?
- Vasodilation
- Blood vessels are more permeable
- WBC leaves the blood vessel
- Histamines are released by connective tissue, WBC, and mast cells
What are histamines?
They are released by mast cells/damaged WBC’s
- Cause the blood vessels to dilate causing local heat and redness
- Raised temperature reduces pathogen reproduction
- They make the wall of the capillaries leaky forcing plasma, WBC’s and antibodies out of the capillary - which causes swelling (oedema) and pain
What is phagocytosis seen in association with?
Inflammation
