1.6 Human defence systems

non-specific

• skin
• nose
• eyes
• trachea and bronchi
• stomach
• phagocytosis

Specific

• antibody production
• antitoxin production

Skin

Impermeable physical barrier and if it is cut or grazed it immediately begins to heal itself, often by forming a scab

Nose

Cells in the nose produce mucus trapping pathogens before they can enter the lungs, has hairs which act as a physical barrier.

Eyes

Tears contain antibacterial enzymes. Eyelashes act as a physical barrier

Trachea and Bronchi

Cilia line the trachea, they waft their hairs and move the mucus containing pathogens towards the throat where they are then swallowed and killed the the stomach. Goblet cells create the mucus in order to trap the pathogens.

Stomach

It has hydrochloric acid that kills pathogens that were caught in the mucus or consumed

Phagocytes and Phagocytosis (wbc)

Phagocytes surround any pathogens and engulf them. They are attracted to pathogens and bind to them. The phagocytes membrane surrounds the pathogen and enzymes found inside the cell break down the pathogen in order to destroy it

Lymphocytes/antibody production (wbc)

They recognise proteins on the surface of pathogens called antigens and produce antibodies. This can take a few days, during which time you may feel ill. The antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them.

Lymphocytes/antitoxins (wbc)

produce antitoxins to neutralise these toxins. Both the antibodies and antitoxins are highly specific to the antigen on the pathogen