Human Defence Flashcards
What four primary defences stop pathogens from entering our body?
Skin
Stomach acid
Nose hair
Mucus and cilia
What job do scabs do to stop pathogens and how do they do it?
Scabs are formed from blood clotting. When you get a wound, special blood cells called platelets stick together, and react with other proteins to build a clot. This clot is made from a stringy protein that stretches across the wound, pulls the edges together and plugs the gap between them. This helps to stop any more blood from escaping, but also stops bacteria from getting in.
What job do tears and eyelashes do to stop pathogens and how do they do it?
Your eyelashes act as a barrier, which protects the eye when it is open. They trap dirt and microorganisms, preventing them from entering the eye and causing infection. Tears have a high salt content that essentially dessicates or dries up any microorganisms. They also washout any microorganisms that enter the eye, keeping it clean.
What job does stomach acid do to stop pathogens and how does it do it?
Your stomach contains an acid called hydrochloric acid (HCl). This acid is used to breakdown food. It has pH of 2 and is very corrosive. The stomach is coated with a special lining to prevent the acid corroding the wall away. However, any microorganisms that enter our body through the nose/mouth end up in the stomach and its acid, which then destroys their cell walls and kills them.
What job do the hairs in our nose do to stop pathogens and how do they do it?
Hair in the nose is one of the body’s first lines of defence against microorganisms. When you breathe in oxygen, you are also breathing in whatever solid particles are contained in that air. The hair contained in the nostrils helps to trap the larger particles in a sticky layer of mucus (snot). This can then be removed from the nose through blowing or swallowing the mucus, which is then taken care of in the stomach.
What job does skin do to stop pathogens and how does it do it?
Our skin is our body’s large organ and first line of defence. The different layers of skin literally block the microorganisms like a force field. Microorganisms, especially bacteria, live on our skin because it can’t get in. The top layer (called epidermis) sheds all the time. Getting rid of old skin means we are also getting rid of a lot of the microorganisms and bacteria with it. This keeps them from staying on our bodies for too long.
What job does the cilia and mucus do to stop pathogens and how do they do it?
There are some especially adapted cells in our trachea (windpipe) which contain cilia (hair-like projections). There are mucus producing cells mixed in with the ciliated cells to help keep a fresh lining of mucus in our airways. This sticky layer of mucus traps the majority of microorganisms and large particles which enter the body. The cilia sweep the mucus containing the trapped microorganisms into the stomach.
