3.1.6 Human Defence Systems

In this lesson, we will explore the non-specific defence systems of the human body, which act as the first line of defence against pathogens. We will discuss the key components of these defence systems, including the skin, nose, trachea and bronchi, and stomach. Additionally, we will delve into the role of the immune system in protecting the body against diseases caused by pathogens.

Non-Specific Defence Systems

• Skin: The skin acts as a physical barrier, preventing the entry of pathogens. Multiple layers of skin cells, along with sweat and sebum (oily substance), help inhibit the growth of microorganismsSingle-celled organisms including bacteria, fungi, and viruses. on the skin surface.
• Nose: The nose filters and traps pathogens from the air before they enter the respiratory system. Nose hair and mucus lining the nasal passages trap and remove pathogens.
• Trachea and Bronchi: The trachea and bronchi contain mucus-producing cells and cilia, which help trap and remove pathogens from the respiratory system.
• Stomach: The stomach's acidic environment serves as a defence mechanism against ingested pathogens, as many microorganisms cannot survive the low pH.

The Immune System

The immune system identifies and distinguishes between self and non-self molecules, including pathogens. Upon detecting a pathogen, the immune system initiates a response to destroy or neutralise it, preventing further infection.

White Blood Cells:

• Phagocytosis: Some white blood cells, such as macrophages and neutrophils, engulf and destroy pathogens through phagocytosis.
• Antibody Production: B-lymphocytes produce antibodies that bind to specific pathogens, marking them for destruction by other immune cells.
• Antitoxin Production: Some white blood cells, such as plasma cells, produce antitoxins that neutralise toxins released by certain pathogens.

Immune Response:

• Primary and Secondary Response: The immune system mounts a primary response upon initial exposure to a pathogen. Subsequent exposures lead to a faster and stronger secondary response due to the presence of memoryA unified system that stores both data and program instructions in the same location. cells.
• Cell-Mediated and Humoral Response: The immune response involves both cell-mediated (involving T-lymphocytes) and humoral (involving antibodies) components.

Conclusion

The human body possesses non-specific defence systems, such as the skin, nose, trachea and bronchi, and stomach, that act as physical barriers and help prevent the entry and spread of pathogens. The immune system plays a crucial role in recognising and responding to pathogens, utilising white blood cells to destroy or neutralise them. Understanding the non-specific defence systems and the immune response is essential for comprehending how the human body defends itself against diseases caused by pathogens.