How Our Bodies Fight Disease (1955)

[Music] Tommy's sick he runs a temperature and can't go out to play we all get sick from time to time in many cases sickness is caused by tiny tiny germs they are so small that we have to use a microscope to see them this is what germs look like through the microscope we call such small forms of life bacteria there are bacteria all around us some even in the air fortunately our body has ways to defend itself against bacteria which may cause disease our entire body is covered with skin the skin is our body's first line of defense against harmful bacteria this drawing shows a cut through the skin greatly enlarged the outer layer of the skin wears off all the time but from below new skin cells come up to replace the old ones as long as there are no cracks in the skin bacteria cannot break through it easily that's why it's important to take good care of our skin and wash it regularly bacteria can enter the body where there is no skin to stop them as through the nose and mouth but even the mouth the throat and the windpipe are lined with a thin coating which takes the place of the skin it is called a mucous membrane the mucous membrane is covered with a sticky liquid called mucus which moves all the time this drawing shows how dirt and germs fall upon the moving mucus they stick to it and are carried out of the body sometimes we injure the skin and open the way for bacteria to enter the body the fight against bacteria begins with an inflammation something like the red swelling around the cut on your finger this is the signal for special cells in the blood called white blood cells to attack the bacteria they squeeze through the weakened walls of small blood vessels in the inflamed body tissue and attack the germs through the microscope we can actually see white cells attacking and eating up bacteria after a while white blood cells build a wall around the bacteria with the help of other body juices on net forms around bacteria eventually the infected spot clears up and the body gets well again some wounds open the way for germs to penetrate deeper then our body uses a second defense system the lymphatic system suppose a nail pierces through the skin and carries germs into the body a fluid called the lymph fluid carries the germs to lymph nodes a kind of trap that consists of many many passages lined with millions of white blood cells remember white blood cells can devour bacteria and this is exactly what happens bacteria carried by the lymph fluid to the lymph nodes are gradually destroyed by the white blood cells there are many lymph passages throughout our whole body there are for instance lymph passages in the neck and in the chest and still others in the regions of the stomach and the intestine sometimes we get sick because bacteria pass or survived the first and second line of defense and enter the blood then the third line of defense goes into action the blood system this system consists of the heart with all the blood vessels the liver and the spleen in this picture you can see blood flowing through a healthy blood vessel the walls of such a healthy blood vessel are strong strong enough to keep the bacteria inside the blood vessel so that they cannot break through to other parts of the body the bacteria stay inside the blood vessels in this drawing we'll watch some bacteria move through the bloodstream first they enter the right half of the heart then they pass through the lungs and back to the left half and from there they're carried all over the body eventually the germs reach the liver and the spleen the liver and the spleen act like filters for the blood system in the liver and the spleen blood flows very slowly through many many very narrow passages lined with white blood cells the white blood cells attack and destroy the bacteria as they try to squeeze through the narrow passages this is why we call the blood system the body's third line of defense but our body has still a fourth line of defense oftentimes after we've been sick our blood stream remains filled with chemical substances produced by our body to fight the germs which had made a sick these substances are called antibodies sometimes doctors help us make our own antibodies they give us an injection of germs called a vaccination too weak to make us really sick but strong enough to produce antibodies in our blood to understand this better let's look at a drawing the black dots are the germs and the large shapes represent white blood cells here the white blood cells do not seem able to attack the germs and destroy them look at the black bars they are antibodies it seems as if the antibodies were attaching themselves to the germs making them stick together now the white blood cells are able to attack clumps of germs and swallow them gradually the white blood cells dispose of the germs but antibodies remain in the blood they protect us against future attacks of the same disease you all have probably had some vaccine injected into your body by your physician soon antibodies begin to form in your blood and they protect you from the disease against which you are vaccinated at least for a while check with your doctor or school nurse from time to time to see whether you need a vaccination in this film we've seen the main defenses of our body in the fight against disease they are first the skin and the mucus they prevent most bacteria from entering deep into the body tissue second the lymph system which catches bacteria that had penetrated deeper into the body thirdly the blood system which filters out the bacteria finally the antibodies made in the bloodstream which guarded from catching the same disease again when you eat well and sleep well and take good care of yourself you too are helping your body to keep up a strong defense against disease [Music]