Our Immune System

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Slide 1

 

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.

Slide 2

 

First lines of defence

skin prevents entry

tears antibacterial enzymes

saliva antibacterial enzymes

stomach acid low pH kills harmful microbes

mucus linings traps dirt and microbes

“good” gut bacteria out compete bad

Slide 3

 

Pathogens

= disease causing micro-organisms

bacteria

virus

fungi,

protozoa,

parasite,

prion

Slide 4

 

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

Slide 5

 

Phagocytes

Slide 6

 

Phagocytes

Monocytes and macrophages

Provide a non-specific response to infection

Slide 7

 

Phagocytosis

Stages in phagocytosis

Phagocyte detects chemicals released by a foreign intruder (e.g. bacteria)

Phagocyte moves up the concentration gradient towards the intruder

The phagocyte adheres to the foreign cell and engulfs it in a vacuole by an infolding of the cell membrane.

Lysosomes (organelles which are rich in digestive enzymes & found in the phagocytes cytoplasm) fuse with the vacuole & release their contents into it.

Slide 8

 

Phagocytosis

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

Slide 9

 

Pus

An accumulation of : -

dead phagocytes

destroyed bacteria

dead cells

Slide 10

 

Lymphocyte

Slide 11

 

Lymphocytes

Provide a specific immune response to

infectious diseases.