The Immune System

Primary Defences prevent pathogens and parasites from entering the body

The Skin blocks pathogens from entering the body acts as a chemical barrier (produces antimicrobial bacteria) lowers pH preventing the growth of pathogens

Mucous Membranes protect body openings that are exposed some secrete mucus which traps the pathogens and contains antimicrobial enzymes

note: mucus and mucous are spelt differently

The Immune Response occurs when the primary defenses are breached

An Immune Response is the body's reaction to a foreign antigen identified on the cells surface

Antigens are molecules found on the surface of cellsusually made up of proteins or polysaccharides

Main Stages of the Immune Response are:

1. Phagocytosis a phagocyte recognises the antigens on a pathogen the phagocyte englufs the pathogen  the pathogen is now contained in a phagocytic vacuole a lysome fuses the the phagocytic vacuole allowing the enzymes to break down the pathogen and absorb it into the cytoplasm the phagocyte then presents the pathogen's antigens by sticking them on its surface to activate other immune system cells  

A Phagocyte is type of white blood cell that carries out phagocytosis. They are found in the blood and in the tissues and are the 'first response' cells

New Page