Human Body Defence System

Study Notes

Non-Specific Body Defence

Skin acts as a physical barrier preventing pathogens from entering the body.
White blood cells engulf and destroy pathogens through phagocytosis, a process where they ingest and break down foreign particles.

Specific Body Defence

Immunity provides the body with the ability to fight pathogens by producing antibodies.

First Line of Body Defence

Skin

The skin acts as a barrier, allowing pathogens to enter only through wounds.
Sweat and sebum contain chemicals that kill microorganisms, acting as a chemical barrier.

Mucous Membrane

Lines the digestive and respiratory tracts.
Earwax, tears, and vaginal secretions contain antimicrobial substances that kill microorganisms.

Second Line of Body Defence

White blood cells use enzymes to digest pathogens through phagocytosis.

Third Line of Body Defence

Immunity is the body's ability to fight off pathogens before infection occurs.

Non-Specific Body Defence

The body has a first, second, and third line of defence against pathogens
The first line of defence is non-specific, meaning it acts against all types of pathogens
It includes physical barriers like skin and mucous membranes
Sweat and sebum on the skin have antimicrobial properties
The second line of defence is also non-specific and involves white blood cells that engulf pathogens through phagocytosis

Specific Body Defence

The third line of defence is specific, meaning it acts against individual pathogens by producing antibodies
Antibodies are proteins that bind to specific pathogens and mark them for destruction by other cells of the immune system.
The body can remember specific pathogens encountered and mount a faster and more effective response to them upon re-exposure. This is known as immunity.

First Line of Defence

The skin is the first and most important barrier against pathogens, preventing entry unless wounded.
Mucous membranes line the digestive and respiratory tracts, trapping pathogens and preventing them from harming the body
Earwax, tears and vaginal secretions contain antimicrobial compounds that kill microorganisms

Second Line of Defence

White blood cells (leukocytes) are a key part of the body's second line of defence.
Different types of white blood cells like macrophages and neutrophils use enzymes like lysosomes to destroy pathogens through phagocytosis.

Third Line of Defence

The adaptive immune system makes up the body's third line of defence.
When pathogens enter the body, specific white blood cells called lymphocytes are stimulated to produce antibodies.
Antibodies bind to specific antigens on the surface of pathogens, marking them for destruction.
Lymphocytes can remember specific antigens, allowing the body to mount a quicker and more effective immune response upon re-exposure to that pathogen.

Description

Test your understanding of the human body's defense mechanisms against pathogens. This quiz covers both non-specific and specific body defenses, including the roles of skin, white blood cells, and the immune system. Challenge yourself and deepen your knowledge of how your body protects itself from infections.