Barrier Defenses Immune System: The Body's Fortifications

If a pathogen tries to enter the body, then it must first pass through outer shields. If these shields stop the germ before it reaches the blood, then the barrier defenses immune system has done its job.

If a barrier is made of a solid layer of cells that physically blocks an invader, then it is a physical defense. If the skin provides this solid covering for the body, then the statement is true.

If germs enter the nose, then they need to be stopped before reaching the lungs. If a thick, sticky fluid catches these germs like flypaper, then that fluid is mucus.

If a defense uses a substance to destroy a germ through a chemical reaction, then it is a chemical barrier. If stomach acid is strong enough to dissolve the outer shell of a bacteria, then it is part of the barrier defenses immune system.

If a structure acts as a physical shield or a sticky trap, then it is a physical barrier. If skin, eyelashes, and mucus all physically block or catch germs, then they are correct. Stomach acid is chemical, and white blood cells are part of the second line of defense.

If mucus traps germs in the throat, then the body needs a way to remove that mucus. If tiny hairs move in a wave to push the dirty mucus away from the lungs, then they are cilia performing a barrier task.

If "good" bacteria live on the skin, then there is no room for "bad" germs to land. If the bad germs cannot find a place to stay, then the barrier defenses immune system is working correctly.

If a germ lands on your eye, then it needs to be destroyed immediately. If your tears contain a specific enzyme that breaks down bacterial cell walls, then that enzyme is lysozyme.

If most germs prefer a neutral environment, then changing the ph of the skin makes it harder for them to live. If sweat contains acids that lower the skin's ph, then it is helping the body stay safe.

If the skin blocks a virus, a bacteria, and a piece of dust using the same wall, then it is not picking a specific target. If it treats every invader with the same barrier defenses immune system response, then the statement is true.

If a germ or irritant gets into your throat or nose, then the body needs to eject it fast. If the body uses a sudden, automatic blast of air to push the invader out, then it is using a reflex.

If a germ tries to stay inside a tube like the urinary tract, then it must hold on tight. If the body uses a flow of liquid to physically wash the germs out of the body, then urinating is a mechanical barrier.

If the first line of defense is meant to stop an enemy at the very edge of the territory, then it must be an outer structure. If the castle walls and moat are the first things an invader hits, then they represent the barrier defenses immune system.

If the skin is the primary shield of the body, then any opening in the skin is a hole in that shield. If the germ gets through that hole, then it has moved past the first line of defense.

If an internal area is open to the outside world, then it cannot have dry skin. If these areas stay wet and produce mucus to catch germs, then they are correctly called mucous membranes.

If a barrier uses a liquid or a chemical reaction to stop a germ, then it is chemical. If saliva, stomach acid, tears, and sweat all use chemicals or enzymes to fight germs, then they are correct. Fingernails are a physical structure.

If cilia move mucus up to the back of the throat, then the body must decide what to do with it. If you swallow that mucus, then the germs go to the stomach where the acid destroys them.

If the skin needs to stay waterproof and chemically protected, then it must secrete a special oil. If this oil contains fatty acids that stop bacteria from growing, then that oil is called sebum.

If the body can stop a germ from ever entering the blood, then the person will not get sick. If the first line of defense stops almost all germs every day, then it is the most important way we prevent infection.

If the ear canal is a hole that leads deep into the head, then it needs protection. If the sticky earwax catches invaders before they reach the eardrum, then it is a successful barrier.