Second line of defence Flashcards
What does the second line of defence include
Phagocytosis, Inflammation, Fever
What does the immune system consist of
Lymph nodes, Lymph vessels, Lymphoid tissues (Thymus, Spleen, Bone marrow), Leucocytes (White blood cells)
What does the immune system do
Carries out both specific and non-specific responses
Lymph vessel and movement through it
Lymph vessel has valves, blind-ended tubes, thin, not muscular, Lymph moves through the lymph vessel via contractions of the muscle pushing the lymph up which is then stopped from going back down by the valves
What does the lymphatic system do
Drains intercellular fluid back to the heart and circulatory system
White blood cells/leucocytes
can leave the blood capillaries and migrate to places of infection or injury
Macrophages
leucocyte that can undergo a specific and non-specific defence, phagocytes, release substances which destroy micro-organisms
Lymphocytes (B and T cells)
leucocytes that can only undergo a specific defence only, produced in bone marrow and lymphoid tissue, circulate through tissue, blood, lymph
Phagocyte
white blood cell that is capable of engulfing and digesting micro-organisms and cell debris
Cause of inflammation
Response to tissue damage
Purpose of inflammation (4)
Reduce spread, destroy and stop further entry of pathogens, Remove damaged tissue/cell debris, Begin repair of damaged tissues
5 signs of inflammation
Redness, heat, swelling, pus, pain
What causes redness
increased blood flow, increased Vaso dilation and increased capillary permeability
What causes heat
increased blood flow, increased Vaso dilation and increased capillary permeability
What causes swelling
leaking fluid from the blood vessels, increased Vaso dilation and increased capillary permeability
What causes pus
dead phagocytes that have been drawn to the area
What causes pain
pain receptors being stimulated by increased blood flow pressing on them
Inflammatory response
Non-specific, When cell damage occurs, mast cells (specialised leucocytes that line tissues) release histamine and heparin into intercellular fluid, Histamine increases blood flow to the area by increasing capillary permeability (spreads lining cells out) and causing blood vessels to dilate, Heparin prevents immediate clotting which allows leucocytes to get to the area that is infected/injured, Phagocytes are attracted by chemicals from the mast cells and move in to conduct phagocytosis
Fever
Non-specific response, elevation of body temperature
Why are fevers beneficial (4)
Increases production of killer T cells (which speeds up the cell mediated immune response, Increases metabolic rate which speeds up tissue repair, Increases heart rate/blood flow which enables lymphocytes to reach sites of infection faster, Creates non-optimum temperature/high temperature which inhibits/kills pathogen
When can a fever be harmfull
body temperature gets too high (44-45 degrees) as enzymes start to denature
What causes a fever
Pathogens release chemicals called pyrogens which causes the sensors in the hypothalamus to increase body temperature, Macrophages respond to the pathogen by ingesting it, releasing a chemical called interleukin 1 which the hypothalamus responds to by increasing the bodies temperature
When the body feels cold whilst a fever is occuring
happens because the “internal thermostat” is raised meaning normal temp=cold, causes body to respond by shivering and vasoconstricting the blood vessels in your skin in an attempt to warm up
Fever has broken
when infection is over and there are no more pyrogens meaning the hypothalamus will re-set the set point back to 37.5 meaning the body needs to cool down by sweating and vaso-dilation
