1.3 The Defence System
Completion requirements
Unit D
Module 8 ~ Lesson 1
The First Line of Defence
The human body is constantly under siege by a variety of micro-organisms. These organisms are looking to enter and establish a home in which to live and reproduce. Many of these foreign invaders are harmless. However, a large number of these bacteria, protozoa,
fungi, and viruses are pathogenic and may even be deadly to the body.
The human body uses a number of protective mechanisms to defend itself from these potentially hostile pathogens. The first line of defence is to deny the micro-organisms entry into the body.
The human body uses a number of protective mechanisms to defend itself from these potentially hostile pathogens. The first line of defence is to deny the micro-organisms entry into the body.
The skin is a continuous barrier that prevents access. The epithelial (surface) cells of the skin protect against the billions of organisms you are exposed to on a regular basis. There is additional support at potential weak spots in people's external
covering. For example, tears and eyelashes protect the eyes, cilia and mucus protect the respiratory tract, and stomach acid protects the digestive system. Together, these defences repel the vast majority of pathogens.