Non-specific Animal Defences: Barriers to Pathogens

What are non specific defences

Defences that respond quickly in the same way to all pathogens

What are specific defences

Defences that produce a targeted response against specific pathogens

What is the role of the skin in defence

Acts as a physical barrier preventing pathogen entry

What is sebum

Oily antimicrobial substance produced by skin that lowers pH and inhibits pathogens

What are mucous membranes

Linings in body passages that produce mucus and lysozymes

What is the function of mucus

Traps pathogens preventing them entering tissues

What are lysozymes

Enzymes that destroy pathogens

How do coughing and sneezing defend the body

They expel pathogens from the respiratory system

How do vomiting and diarrhoea defend the body

They remove pathogens from the digestive system

Why is blood clotting important

It seals wounds preventing pathogen entry

What is a scab

Dried blood clot that forms a barrier over a wound

How does wound repair occur

Epidermal cells divide blood vessels regrow and collagen strengthens tissue

What is inflammation

Response to infection or injury causing swelling heat redness and pain

What causes inflammation

Damaged tissues release chemicals affecting blood vessels

How does vasodilation help during inflammation

Increases blood flow and heat reducing pathogen reproduction

Why do blood vessels become more permeable during inflammation

To allow tissue fluid to leak out causing swelling and isolating pathogens

What is an antigen

A unique molecule usually a protein on the surface of cells

What is the function of antigens

Allow the immune system to distinguish self from non self

How does the immune system respond to pathogen antigens

Recognises them as foreign and activates destruction of the pathogen

How are abnormal body cells recognised

They display abnormal antigens that trigger an immune response

Why can transplanted organs be rejected

Their cells have different antigens recognised as foreign

What are toxins in immunity

Foreign antigen molecules recognised by the immune system