3.5 Flashcards
What is immunity?
Immunity is the ability of the body to resist infection by a pathogen or to destroy the organism if it succeeds in invading and infecting the body
What is a pathogen?
A pathogen is a bacterium, virus or other
organism that can cause disease.
What are the 2 types of defence in the immune system?
Physical defences and • Chemical defences
What is the physical defence in the immune system
Epithelial cells form a physical barrier
– Found in skin and inner linings of digestive and
respiratory systems
– Stop pathogens from entering by forming a barrier
Explain the chemical defence in the immune system?
Produced to stop pathogens entering
– Tears, saliva, mucus and stomach acid
Explain the The Second Line of Defence:
The Inflammatory Response
The inflammatory
response is a specialised defence which works at the affected site.
What are mast cells?
Mast cells are cells found in connective tissue
around the body. They are closely related to
white blood cells
• Mast cells contain granules containing
histamine.
What is histamine?
Histamine causes blood vessels to
dilate and capillaries to become more permeable.
When do mast cells become activated?
When injury occurs, mast
cells become “activated” and
release large quantities of
histamine. This results in
blood vessels in the area
undergoing vasodilation, and
capillaries become full of
blood.
What does extra blood flow make the affect area?
makes
the area red, swollen,
inflamed and hot to touch.
This extra blood flow
means that molecules
called phagocytes,
clotting elements and
cytokines accumulate in the area
What are phagocytes?
Phagocytes are white blood cells that engulf (consume) pathogens by a process called phagocytosis
What are phagocytes?
Phagocytes are white blood cells that engulf (consume) pathogens by a process called phagocytosis
Explain phagocytosis?
During phagocytosis, a foreign pathogen is broken
down inside a phagocyte by powerful digestive
enzymes called lysosomes.
• Phagocytes also release molecules called cytoki Cytokines signal to other phagocytes to join them at
the injured site.
Explain cytokines?
Cytokines are protein molecules that act as a
signal to specific white blood cells.
• This causes white blood cells to accumulate at
the site of infection.
• Signals sent out by cytokines increase the number of phagocytes
