6.3 Disease Defences Flashcards
What are the 2 types of surface barriers in the body?
Skin
Mucous membranes
Which glands secrete biochemical defences on the skin?
Sebaceous glands
What does skin secrete to lower the pH?
Lactic acid and fatty acids
What do mucous membranes secrete as a biochemical defence?
Lysozyme to destroy cell walls and cause cell lysis
What is haemostasis?
Clotting - the mechanism by which broken blood vessels are repaired when damaged
What are the key components of a blood clot?
Platelets and fibrin stands
What occurs in primary haemostasis?
Platelets undergo a structural change when activated to form a sticky plug at damaged regions
What occurs in secondary haemostasis?
Fibrin strands form an insoluble mesh of fibres that trap blood cells at the sight of damage
What is a coagulation cascade?
The process by which a blood clot forms
What is the extrinsic pathway in the coagulation casscade?
Factors released by damaged cells
What is the intrinsic pathway in the coagulation casscade?
Factors released by the platelets
What are the main events of the coagulation cascade?
Clotting factors cause platelets to become sticky and adhere to the damaged surface
The factors cause localised vasoconstriction and conversion of prothrombin->thrombin
Thrombin catalyses soluble fibrinogen->fibrin (insoluble)
Fibrin forms a mech around the platelet plug and traps blood cells for a temporary clot
How are clots broken down?
Plasmin dissolves the clot when damage is repaired
What does thrombin do?
Catalyse Fibrinogen (soluble) -> fibrin (insoluble)
What do clotting factors do to prothrombin?
Convert it to thrombin
If there is a rupture of an atherosclerotic plaque in the coronary arteries what happens?
There will be clotting triggering a thrombus which will block blood flow to cardiac tissue
Is the innate immune system specific or non specific?
Non specific
What are the principle components of the innate immune system?
Phagocytic white blood cells
(Inflammation
Fever
Antimicrobial chemicals)
What are the two key components of the innate immune system?
Non specific
Non adaptive
Describe phagocytosis
Process by which solid material is ingested by the cell (endocytosis)
Describe phagocytosis
Leukocytes circulate in the blood and move into body tissue in response to infection
Damaged tissue releases chemicals which draw white blood cells to infection site
Pathogens are engulfed when cellular extensions surround the pathogens and fuse to form internal vesicles
The vesicle uses to a lysosome which digests the pathogen
What is the name of the cellular extensions that engulf pathogens into phagocytes?
Pseudopodia
What name is given to a pathogen fused to a lysosome?
Phagolysosome
What may a phagocyte do after digesting a pathogen?
Present the antigen on the surface to stimulate the third line of defence
What are the first, second and third lines of defence?
1 - barriers
2 - innate immune system
3 - adaptive immune system
What coordinates the adaptive immune system?
lymphocytes
What are the 2 types of lymphocytes?
B lymphocytes
Helper T lymphocytes
What do B lymphocytes do?
Antibody producing cells that recognise and target specific pathogenic fragments (antigens)
What do helper T cells do?
Release cytokines to activate specific B lymphocytes
What are cytokines?
Chemicals which activate specific B lymphocytes
Describe the activation of the adaptive immune system
Antigens presented by phagocytic leukocytes migrate to the lymph nodes and activate specific helper T lymphocytes
These release cytokines to activate specific B lymphocytes capable of producing antibodies specific to the antigen
Activated B cells will divide and differentiate into short lived plasma cells that produce high amount of specific antibody
A small proportion of activated B cells and helper T cells will develop into memory cells to provide long-lasting immunity
What are antibodies composed of?
4 polypeptide chains held together by disulphide bonds in a Y shape
Where do antigens bind on antibodies?
On the ends of the arms of the Y
What do antibodies do?
Label pathogens for the rest of the immune system
What may antibiotics target?
Prokaryote specific cells features
Cell wall synthesis/DNA synthesis/Cell membranes/70s Ribosomes/Metabolic enzymes
What are narrow spectrum antibiotics?
Effective against a small range of bacteria
What are wide spectrum antibiotics?
Effective against a large range of bacteria
When was penecillin discovered and by who?
Fleming in 1928
What does HIV stand for?
Human Immunodeficient Virus
What does HIV do?
It is a retrovirus that infects helper T cells - disabling the adaptive immune system
How does HIV immunity occur?
It occurs in people who lack the CD4+ receptor on T cells
How is HIV transmitted?
Exchange of bodily fluids (blood, sexual excretions, breast milk etc…)
