DEFENCE MECHANISMS Flashcards
what is a pathogen
microorganism with the potential to cause disease
what is an infection
invasion and multiplication of pathogenic microbes
what is disease
when infection causes damage to the individuals vital functions
what is the first line of defense
prevents pathogens from entering the body
first line of defense examples
skin - physical barrier. if broken platelets form a scab acting as a physical barrier
skin - chemical barrier - lysozymes found in tears / mucus destroys peptidoglycan in cell walls of bacteria
stomach - hcl destroys bacteria
cilia - beat to move mucus up and out
which pathogens can pass through the first line of defense
malaria
bubonic plague
influenza
cell recognition
self - body’s own cells and molecules
non-self - any foreign material / cell
what is an antigen
molecule / protein that stimulates an immune response and is found on the surface
what can antigens recognise
pathogens
non-self material
toxins
tumor cells
describe phagocytosis
1.Pathogen is recognised as foreign
2. Phagocyte moves to it (chemoattractants
present)
3. Phagocyte attaches to pathogen by surface
receptors
4. Pathogen is engulfed by phagocyte (endocytosis)
5. A phagosome (membrane bound vesicle
containing pathogen) forms inside phagocyte
6. Lysosomes (with hydrolytic enzymes) fuse into
phagosome & release lysozymes into phagosome
7. Pathogen is completely digested- harmless
products excreted / used
8. Phagocyte displays antigenic components on its
external surface (antigen presentation), for
effects of phagocytosis
causes inflammation at infection site
swollen area contains dead bacteria and phagocytes (pus)
damaged tissues release histamines causing dilation of blood vessels
increasing rate of antibody and WBC delivery to site of infection
