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Human Defence Systems
Communicable Diseases are spread by PATHOGENS (microorganisms that cause disease). The body has several DEFENCES to prevent pathogens from entering the body and infecting a person.
The Body's DEFENCE SYSTEM
1. The SKIN
- Provides a protective BARRIER against pathogens.
- Produces ANTIMICROBIAL SUBSTANCES to actively kill potential threats.
2. The NOSE
- HAIRS and MUCUS in the nose serve as physical traps for dust, microbes, and other particles.
- Helps prevent the entry of pathogens into the respiratory system.
3. The TRACHEA and BRONCHI (Air Passages)
- Secrete MUCUS to capture and trap pathogens.
- Lined with CILIA, tiny hair-like structures that move mucus loaded with trapped pathogens OUT OF the respiratory system to the back of the throat. From there it is swallowed and goes into the STOMACH.
4.The STOMACH:
- Produces HYDROCHLORIC ACID, a strong acid that destroys pathogens ingested through food or drink.
If these defences fail and the pathogens enters the blood stream of a person, they are said to be INFECTED. From this stage the IMMUNE SYSTEM kicks in to try and kill the pathogens.
The IMMUNE SYSTEM
The immune system is mainly made up of WHITE BLOOD CELLS which can fight pathogens in THREE different ways:
1. PHAGOCYTOSIS:
- A process where WHITE BLOOD CELLS (phagocytes) ENGULF and DIGEST invading pathogens.
- The phagocytes goes up to a pathogen and changes its shape to SURROUND the pathogen. It then releases ENZYMES to digest it.
2. ANTIBODY PRODUCTION:
- Pathogens have unique markers on their surface called ANTIGENS, which white blood cells known as LYMPHOCYTES can identify.
- The lymphocytes produce ANTIBODIES; special proteins with specific shapes to bind to the antigens of a pathogen and marks them for destruction.
- When a pathogen is marked, it makes it easier for PHAGOCYTES to find them and engulf them.
- Once all of the pathogens of a disease have been killed, most of the lymphocytes that produced the antibodies to kill them die off as they are no longer needed. However a few lymphocytes still remain in the body, just in case the pathogen REAPPEARS.
- The lymphocytes that remain are known as MEMORY CELLS and these produce MORE antibodies RAPIDLY so that the pathogens die off quickly before the symptoms of the disease have even appeared.
- If this occurs, we say that the person is IMMUNE to the disease and pathogen.
3. ANTITOXIN PRODUCTION:
- These help with BACTERIAL infections
- Bacteria produce poisons known as TOXINS which cause harm to body cells
- ANTITOXINS are substances that neutralise the toxins released by invading bacteria.
Human Defence Systems
Communicable Diseases are spread by PATHOGENS (microorganisms that cause disease). The body has several DEFENCES to prevent pathogens from entering the body and infecting a person.
The Body's DEFENCE SYSTEM
1. The SKIN
- Provides a protective BARRIER against pathogens.
- Produces ANTIMICROBIAL SUBSTANCES to actively kill potential threats.
2. The NOSE
- HAIRS and MUCUS in the nose serve as physical traps for dust, microbes, and other particles.
- Helps prevent the entry of pathogens into the respiratory system.
3. The TRACHEA and BRONCHI (Air Passages)
- Secrete MUCUS to capture and trap pathogens.
- Lined with CILIA, tiny hair-like structures that move mucus loaded with trapped pathogens OUT OF the respiratory system to the back of the throat. From there it is swallowed and goes into the STOMACH.
4.The STOMACH:
- Produces HYDROCHLORIC ACID, a strong acid that destroys pathogens ingested through food or drink.
If these defences fail and the pathogens enters the blood stream of a person, they are said to be INFECTED. From this stage the IMMUNE SYSTEM kicks in to try and kill the pathogens.
The IMMUNE SYSTEM
The immune system is mainly made up of WHITE BLOOD CELLS which can fight pathogens in THREE different ways:
1. PHAGOCYTOSIS:
- A process where WHITE BLOOD CELLS (phagocytes) ENGULF and DIGEST invading pathogens.
- The phagocytes goes up to a pathogen and changes its shape to SURROUND the pathogen. It then releases ENZYMES to digest it.
2. ANTIBODY PRODUCTION:
- Pathogens have unique markers on their surface called ANTIGENS, which white blood cells known as LYMPHOCYTES can identify.
- The lymphocytes produce ANTIBODIES; special proteins with specific shapes to bind to the antigens of a pathogen and marks them for destruction.
- When a pathogen is marked, it makes it easier for PHAGOCYTES to find them and engulf them.
- Once all of the pathogens of a disease have been killed, most of the lymphocytes that produced the antibodies to kill them die off as they are no longer needed. However a few lymphocytes still remain in the body, just in case the pathogen REAPPEARS.
- The lymphocytes that remain are known as MEMORY CELLS and these produce MORE antibodies RAPIDLY so that the pathogens die off quickly before the symptoms of the disease have even appeared.
- If this occurs, we say that the person is IMMUNE to the disease and pathogen.
3. ANTITOXIN PRODUCTION:
- These help with BACTERIAL infections
- Bacteria produce poisons known as TOXINS which cause harm to body cells
- ANTITOXINS are substances that neutralise the toxins released by invading bacteria.
