human defence system

immunity

ability to prevent infection

two parts human defence system

general(non specific acts against all pathogens) and specific(immune system)

pathogen

organism that causes disease

what is the general defence system

acts as barrier and prevents pathogens from entering boy

first line general defence system

the skin. physicoal barrier prevents pathogens passing through. . blood clotting prevents entry further pathogens. hydrochloric acid kills pathogens in stomach.

name two places in body that has a mucous membrane lining

respiratory tract digestive tract

what is second line general defence system

white blood cells destroying pathogens

phagocytic white blood cells

engulf and destroy harmful bacteria and viruses

inflammation

infected cvells release chemical causes blood capillaries become more porous. causes swelling brings white blood cells to area of infection. prevents bacteria viruses reproducing

specific defence system

attack particular pathogens. functions by production of antibodies or when white blood cells destroy body cells infected by pathogen

organs in human body that are specific to the defence system

thymus gland lymph nods tonsils spleen

antigen

foreign molecule causes production antibodies. include molecules from viruses cell walls bacteria and fungi

part of virus that is recognised by antibodies

antigens

antibody

protein produced by white blood cells in response to an antigen. is to inactivate an antigen

why is an antibody said to be specific

acts on one particular antigen.

lymphocytes

white blood cells formed in the bone marrow B -lymphocytes mature in(bone marrow) and T-lymphocytes mature in(thymus gland).

fucntion B lymphocytes

produce antibodies. some remain memory cells

helper t cells

recognise antigens stimulate b cells activate killer cells

killer t cells

attack infected cells

suppressor t cells

stop immune responses

memory t cells

long term protection remember antigens

role of memory B cells

remain in body. allows quicker production antibodies to destroy pathogen

why do we usually not suffer same infection more then once

some lymphocytes(memory cells) allow for quicker production antibodes to destroy pathogen

induced immunity

ability to resist disease caused by specific pathogens by the production antibodies

types induced immunity

active immunity passive immunity

active immunity

involves production of a persons own antibodies in response antigens. long lasting

natural active immunity

occurs when pathogen enters body in the normal way

artificial active immunity

when a pathogen is medically introduced into body e.g vaccination

what is a vaccine

non disease causing dose of pathogen which triggers production antibodies.

immunity after a vaccination is simular to immunity after infection explain this

specific antibodies are produced both cases long term immunity will result from both as memory cells will remain in body

what is purpose to receive secondd vacinne

helps increase number antibodies

passive immunity

when individuals are given antibodies that are formed by other organisms. short term resistastance

natural passive immunity

when a child gets antibodies from its mother. e.g antibodies cross the placenta through breast feeding baby

artificial passive immunity

when a person is given a injection containing antibodies made by another organism

immunisation

when antibodies are produced or injected against pathogens

what is meant by immunity

resistance to infection

when should someone receive an antibody rather then a vaccine

if person already has infection