6.2 Flashcards
How is the skin a barrier
Skin keratin stops entry of pathogens and aids in blood clotting
Skin flora prevents colonisation by other bacteria
What are phagocytes
White blood cells that engulf bacteria and other foreign matter - macrophages and neutrophils
What are Neutrophills
Non-specific
Engulf and digest pathogens, acting immediately
What happens during inflammation
Cells become damages White blood cells release histamine Increases blood flow to area by dilating arterioles Takes more white blood cells to area Causes capillaries to become permeable Increases temp, forms oedema
What happens in non - specific phagocytosis
Be catering engulfed by neutrophil
Packaged into phagosome
Lysosomes phospholipid bilayer fuses with that of phagosomes
Releases digestive enzymes, breaking pathogen down
How does the enzyme lysozyme work
Weakens cross links in peptidoglycan cell wall
How does interferon work
Produced by virus-infected cells
Diffuses to surrounding cells to prevent virus from multiplying
Inhibits viral protein synthesis
What are lymphocytes
White blood cells that help fight specific diseases
How does a macrophage become APC
When pathogen is engulfed, antigens are broken down and are added to proteins in cell membrane
How are T helper cells activated
APC binds to T helper cells
CD4 behind to MHC
Secreting cytokines
T helper cells divide into active cells and cloned T memory cells
What do B cells produce
Antibodies
How are B cells cloned
Antigen binds to B cell with a complementary receptor
B cell becomes APC
Active T helper behind to APC and produce cytokines which stimulate the B cell
B cell divides into active B effort and clone B memory cells
B effector cells differentiate into plasma cells
Plasma cells secrete antibodies
What are antibodies
Immunoglobulins
At as labels allowing phagocytes to recognise and destroy them
Specific - each B cell can only produce one type
What happens in specific phagocytosis
Antibodies formed bind to and label antigens
Antibody binds to antibody receptor on macrophage
Macrophage engulfs antibodies and bacterium
Lysosomes fuse wi vacuole, releasing digestive enzymes
What are T killer cells and how do they become active
Stimulated by cytokines in tissue fluid
Bind to other APCs (infected somatic cells become APC)
Produce enzymes causing the cell to lyse
List the barriers to prevent entry
Ear wax Mucus membrane Lysozyme Gastric juices Skin Gut flora Platelet plugs Phagocytes
