Immune system
By the end of the lesson you should be able to Outline the stages in phagocytosis. Describe how antibodies work and how they are specific.
First lines of defence
saliva antibacterial enzymes
skin prevents entry
tears antibacterial enzymes
mucus linings traps dirt and microbes
stomach acid low pH kills harmful microbes
“good” gut bacteria out compete bad
Pathogens
= disease causing micro-organisms
bacteria virus fungi, protozoa, parasite, prion
Second lines of defence
Involves white blood cells Non-specific response
invading pathogens are targeted by macrophages
Specific response
lymphocytes produce chemicals called antibodies that target specific pathogens
Phagocytes
Phagocytes
Monocytes and macrophages Provide a non-specific response to infection
http://www.microbelibrary.org/imag es/tterry/anim/phago053.html
Phagocytosis
Stages in phagocytosis 1. Phagocyte detects chemicals released by a foreign intruder (e.g. bacteria) 2. Phagocyte moves up the concentration gradient towards the intruder 3. The phagocyte adheres to the foreign cell and engulfs it in a vacuole by an infolding of the cell membrane. 4. Lysosomes (organelles which are rich in digestive enzymes & found in the phagocytes cytoplasm) fuse with the vacuole & release their contents into it.
Phagocytosis
5. The bacterium is digested by the enzymes, and the breakdown products are absorbed by the phagocyte. During infection, hundreds of phagocytes are needed. Pus is dead bacteria and phagocytes!
link to phagocytosis
Pus
An accumulation of : dead phagocytes destroyed bacteria dead cells
Lymphocyte
Lymphocytes
Provide a specific immune response to infectious diseases. There are 2 types: - T-cells - B-cells
They produce antibodies.
Antigens
all cells have surface markers called antigens. body can recognise these as self or non-self (foreign)
Specific response
Lymphocytes detect presence of foreign antigens
Stimulated to produce specific proteins called antibodies.
antibodies combine with their specific antigen (like a lock and key)
this renders the pathogen harmless. = primary response
Immunity
= the bodies ability to resist infection can be natural or acquired
Immunological memory
after an infection is fought off some lymphocytes become memory cells. if same pathogen returns memory cells stimulate the produce the specific antibody very rapidly. the infection is fought off before symptoms appear = secondary response vaccines can stimulate same response
Immune system
Can you Outline the stages in phagocytosis. Describe how antibodies work and how they are specific.