Non-specific Animal Defences: Phagocytosis

What is phagocytosis

Non specific defence process where phagocytes engulf and destroy pathogens

What are phagocytes

White blood cells that engulf and digest pathogens

Where are phagocytes found

In blood and body tissues

What are the two main types of phagocyte

Neutrophils and macrophages

What do neutrophils do

Rapidly engulf and destroy pathogens at infection sites

What do macrophages do

Engulf pathogens and present their antigens on the cell surface

Why do macrophages present antigens

To activate other cells in the immune system

What attracts phagocytes to pathogens

Chemicals released by pathogens

What happens first in phagocytosis

Phagocyte recognises and binds to the pathogen

What happens after a phagocyte binds to a pathogen

The phagocyte engulfs the pathogen into a vesicle called a phagosome

What is a phagosome

Vesicle containing an engulfed pathogen

What happens after a phagosome forms

Lysosomes fuse with the phagosome

What are lysosomes

Organelles containing digestive enzymes

What happens when lysosomes fuse with phagosomes

Enzymes digest and destroy the pathogen

What are cytokines

Cell signalling molecules released by phagocytes

What do cytokines do

Attract more phagocytes and increase body temperature

Why does increased body temperature help defence

It inhibits pathogen reproduction and speeds up immune responses

What are opsonins

Chemicals that bind to pathogens making them easier for phagocytes to recognise

How do opsonins help phagocytosis

They improve binding between phagocytes and pathogens

What receptors do phagocytes have

Cell surface receptors that bind to opsonins