When you are sick from a cold or the flu, you may cough, sneeze, or feel tired. Your body temperature even may be pretty high, which means you have a fever! However, after rest (and possibly some medications), you begin to feel better. Have you ever thought about what helps fight off sickness in your body..?
This is all due to your immune system! You can think about the immune system as your body's military or police force. They protect you from invaders such as viruses, bacteria, and other pathogens*. Your immune system has different levels of defense against invaders, each which are controlled by different parts of the body.
*pathogens - dangerous germs that can harm your body
First Line of Defense
The immune system's first step to stop invaders involves the following systems:
Skin - Your skin is the number #1 protector against invaders! They provide a barrier from entering your body and causing damage
Tears/Mucus/Saliva - These do sound pretty gross, but they also help your body protect itself. If pathogen particles get into your eyes, mouth, or nose, these fluids help wash them out
Stomach acid - Inside of your stomach is super strong acid, known as hydrochloric acid (HCl). For regular purposes, the HCl helps digest food by breaking it down into smaller particles. However, HCl also helps protect your body by killing dangerous germs in your stomach
Second Line of Defense
If germs get past the first line of defense, this is how the body may respond:
White Blood Cells -
Your blood doesn't just contain red blood cells. Another large part of your blood cells are known as white blood cells, which are important parts of your immune system. These cells are really cool because they can eat and digest* germs!
*cells that can eat and digest are known as phagocytes
Swelling (aka inflammation) - This happens when you cut yourself and your skin breaks. If you fall off your bike and scrape your knee, swelling will occur in that area. This is done purposely by the body because it attracts more white blood cells to the area that is damaged. If any germs sneaked their way in, these white blood cells will be on the hunt to eat them
Fever - Your normal body temperature is around 97 degrees Fahrenheit, which is the perfect temperature for bacteria and other germs to live in! However, when these germs start doing harm, your body raises its temperature to kill the germs, which results in fever
Third Line of Defense
The immune system's third line of defense is the most intense and most powerful. It is controlled by 2 main systems, known as T and B cells.
Antibodies - To understand the immune system's third line of defense, you must first understand what antibodies are. Antibodies are small y-shaped proteins that attach to germs. They are like flags, marking germs that need to be destroyed by the immune system
B Cells - These cells move around in the body and create antibodies
T Cells - These cells look for the antibodies. Any germ that is marked with an antibody flag will signal the T cells to destroy these germs
Body Systems
Many organs and systems in your body contribute to these three lines of defense. These organs and processes work together to protect you from germs. The most important areas to remember are of the following:
Bone marrow
Thymus
Lymph nodes
Your bone marrow is located in the insides of your bone. It is a spongy layer that is an important part of your immune system. The bone marrow is where blood cells are created, which include white blood cells, T cells, and B cells. After they are created, T and B cells must then travel to specific locations to become mature. The maturation site for B cells is in the bone marrow itself.
While the B cells mature in the bone marrow, T cells need to travel to the Thymus to mature. This organ is right between your lungs. The thymus houses T cells until they are fully matured and ready to circulate through your body. As you become older, your thymus becomes smaller. This is because when you are older, less T cells are being created and maturing.
The last major area of your immune system is known as the lymph node. There are several lymph nodes throughout your body. These little bean-shaped organs are like filters. They remove all the dangerous germs and pathogens from the fluids in your body. You may notice that your lymph nodes are swollen when you are sick. This is because it is working harder to remove all germs from your body.
Sources
Biology for Kids. (n.d.). Retrieved August 16, 2020, from https://www.ducksters.com/science/biology/immune_system.php
The body's first line of defence. (2010, October 10). Retrieved August 16, 2020, from https://www.sciencelearn.org.nz/resources/177-the-body-s-first-line-of-defence
Department of Health & Human Services. (2014, March 30). Immune system. Retrieved August 16, 2020, from https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system
Ghose, T. (2020, July 17). What are antibodies? Retrieved August 16, 2020, from https://www.livescience.com/antibodies.html
Immune System Summary. (2008, August). Retrieved August 16, 2020, from https://www.austincc.edu/apreview/EmphasisItems/Inflammatoryresponse.html
Lymph nodes. (n.d.). Retrieved August 16, 2020, from https://www.healthdirect.gov.au/lymph-nodes
Nishino, M., Priola, A., Carter, B., Ashiku, S. K., Kocher, O. N., & Thurer, R. L. (2006, March 01). The Thymus: A Comprehensive Review. Retrieved August 16, 2020, from https://pubs.rsna.org/doi/full/10.1148/rg.262045213
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