Presentation on theme: "What has happened when a cut in your skin becomes infected? What could have been done to prevent it?"— Presentation transcript:
What has happened when a cut in your skin becomes infected? What could have been done to prevent it?
Your body has a number of defenses against infection. 1 st line of defense against infectious disease includes both chemical and physical defenses. ◦ skin ◦ Mucous membranes ◦ cilia ◦ Saliva and tears ◦ Stomach acid
Your skin serves as both a chemical and a physical barrier against pathogens. The surface cells are hard and have no gaps between them. Sweat acts as a chemical barrier because it contains acids that kill many bacteria. Old skin cells are shed constantly, and the pathogens on these cells are shed, too.
The openings into your body, mouth, eyes, and nose are covered by protective linings called mucous membranes. The mucous that is secreted traps many pathogens and washes them away. Mucous also contains chemicals that attack pathogens.
Some of your body’s mucous membranes are lined with tiny hair-like structures called cilia. Together, cilia and mucus help trap and remove pathogens. As you inhale dust and pathogens get trapped in the mucus of your air passages. The cilia flow together and move the mucus towards your mouth and nose. Coughing, sneezing, or blowing your nose will remove this mucus and the pathogens that were on it.
Can trap pathogens and wash them away. Like mucus, they contain chemicals that will attack pathogens.
Chemicals in your digestive system, including acids in your stomach, kill many pathogens. The normal motions of the digestive system not only move food through your system but also move pathogens out. Bacteria that normally live in your digestive system produce substances that can harm or kill invading bacteria.
The body’s second line of defense after the physical and chemical defenses. Inflammation is your body’s general response to all kinds of injury, from cuts and scrapes to internal damage. Inflammation fights infection and promotes the healing process.
Within seconds after your body is injured, the damaged cells release chemicals that cause blood vessels in the injured area to enlarge. Blood, other fluids, and white blood cells called phagocytes leak out of the enlarged vessels. The phagocytes engulf and destroy pathogens.
Phagocytes also give off substances that cause healing to begin. The fluids, phagocytes, and dead cells that accumulate at the injury site often result in the formation of a thick, white liquid called pus. Eventually, the inflammation process heals the damage, and the inflammation subsides.