6.3 - Defence against Infectious Disease Flashcards
Provide 2 examples of the first line of defence.
- the SKIN: protects external structures
- MUCOUS MEMBRANES: protects internal structures
Provide 3 ways in which mucous membranes assist in the defence against disease.
- sticky, which traps pathogens
- can contain lysozymes which can cause cell lysis
- can be ciliated (hairy) which aids in the removal of pathogens
Define pathogen.
A disease causing organism.
Draw a flowchart to describe how clotting occurs after blood vessel damage.
- the broken vessel releases CLOTTING FACTORS
- these clotting factors cause PLATELETS to become STICKY, which forms a plug around the wound
- these clotting factors also cause VASOCONSTRICTION, reducing blood flow through the damaged region
- these clotting factors convert PROTHROMBIN into THROMBIN, the active form
- thrombin converts FIBRINOGEN into FIBRIN
- a network of fibrin forms a plug around the wound
What can lead to a clot forming in coronary vessels?
Cholesterol deposition, which can lead to blood vessel damage.
What are the consequences of clotting in coronary artery vessels?
- reduces the diameter or lumen of the vessel
- it becomes less elastic
- can lead to blockage and blood cannot pass through
- that part of the heart tissue dies!
What are platelets?
Tiny blood cells that help in clotting.
What is the second line of defence?
A NON-SPECIFIC process which involves phagocytosis, inflammation and fever.
Is the first line of defence specific?
NO.
Is the second line of defence specific?
NO!
What are the roles of phagocytes in the defence against infectious disease?
- phagocytes circulate in the blood and move into body tissues due to the release of histamines
- these cells engulf pathogens
- pathogenic fragments form a vesicle within the cell, and it fuses to the lysosome
- this allows the phagocyte to digest the pathogen
- parts of the pathogen may be presented on the surface of the phagocyte.. VERY important for the third line of defence…….
What is the role of histamine?
- when tissue becomes damaged after the first line of defence has been breached, histamine is released.
- this is a chemical messenger which causes vasodilation
- blood vessels dilate, allowing phagocytes to move into the infected area
What is a phagocyte?
A type of cell capable of engulfing pathogens or other cells.
Is phagocytosis a specific process?
NO.
Is the third line of defence a specific process?
Yes!
The first and second line of defence is innate, whereas the third line of defence is ____________?
ADAPTIVE.
What is an antigen?
A substance that the body recognises as foreign.
What is an antibody?
An immunological protein produced by B LYMPHOCYTES that is specific for a certain antigen.
What is a lymphocyte?
A type of white blood cell which is involved in the third line of defence.
What are the two types of lymphocytes?
B and T lymphocytes.
Explain how the third line of defence works.
- PHAGOCYTES (from the second line of defence) engulf pathogens and present the antigen on its surface
- these antigen-presenting cells migrate to lymph nodes
- here, HELPER T-CELLS are activated
- these helper T cells activate specific B-CELLS
- activated B cells divide and differentiate into PLASMA B-CELLS
- these plasma B cells produce specific ANTIBODIES
- antibodies target the specific antigen and help to destroy the pathogen
- a portion of B and T cells will remain as memory cells to provide long lasting immunity against the specific antigen
What is a lymph node?
Specialised small organs which form the lymphatic system, helps to filter substances travelling through the lymph and contains lymphocytes.
What is an antibiotic?
A chemical which kills or inhibits the growth of bacteria.
List two ways in which antibiotics work.
- prevent bacterial cell wall formation (they cannot live without this)
- target the 70S ribosome (cells need to make proteins or else they die!!)
