You know that you can do many things to keep yourself healthy by making smart lifestyle choices. At the same time, your body works hard to protect you from illness, too. In this activity, you will learn about some of the features of your body that protect it from infection and disease.

The first lines of defence against illness that your body has are its physical and chemical defences. These features of the body keep the agents that cause disease (pathogens) from entering your body.

Your body's largest organ and its major protective barrier from disease is your skin. It prevents pathogens from entering your body, which is why you need to be especially careful to keep cuts and scrapes very clean. Your body also produces oil and perspiration (sweat). Not many pathogens can survive in the acidic or salty conditions sweat and oil produce on your skin.

Your body protects you from pathogens in other ways, too:

• Tears protect your eyes from pathogens.

• Areas of the body that are open to the environment (such as your nose, mouth, and ears) as well as some internal organs are lined with mucous membranes. These are layers of cells that produce a sticky, salty substance called mucus which prevents bacteria and other pathogens from passing through the layers of your skin.

• Many of these openings are also lined with hair and cilia (tiny hairs) that trap pathogens before they enter the body.

• Pathogens that make it to the stomach are usually destroyed by the acids in the lining of the stomach. These work similar to mucus, tears, saliva, and sweat to break down the cells of the pathogens.

If pathogens do enter your body, the white blood cells that circulate through your blood fight bacteria and other pathogens. As well, your temperature may rise. Your body will use your fever to slow down the growth or movement of pathogens and speed up your body's responses to them.

In the next activity, you will learn about what the body does to combat illness if a pathogen makes it through these defences.

Look at the image above. The white blood cell has a flexible shape to help it take in disease organisms. Bacteria are "digested" inside the white blood cell.

Click on the + sign if you would like to look at this image more closely.