The Respiratory System and COVID-19


We, as humans, need oxygen so that we can respire and produce the energy that we need for everything that our bodies do. The respiratory system is what allows humans to breathe by the exchange of oxygen and carbon dioxide, into and out of the lungs. When we inspire, oxygen diffuses into the lungs and carbon dioxide diffuses out; during expiration, the opposite occurs. This essential oxygen is transported in the air to the lungs when we breathe in – it passes first through the mouth or nose where the air is warmed and moistened, and then into the throat via the larynx, down the trachea and finally enters the lungs.

To start this process the diaphragm contracts, making it lower with the external intercostal muscles also contracting. As a result, the thoracic cavity increases in size along with the lungs, meaning that the pressure inside them decreases. To balance out this new lower pressure, air rushes into the lungs from the outside. This intake travels down through either one of the two bronchi to the left or right lung, which then split up into smaller bronchioles further splitting into even more tiny air sacs called alveoli where gas exchange takes place.

Oxygen now diffuses into the blood vessels near the walls of the alveoli from a high to low concentration; carbon dioxide diffuses out of the blood also from a high to low concentration. This process is gaseous exchange and is essential for our survival. To increase the efficiency, these hollow sacs are adapted for their specific function in multiple ways.

Firstly, they are very thin walled so that the gases have a small distance to diffuse, speeding up the rate of exchange. They are also folded giving the lungs a massive surface area to allow for a greater amount of gas exchange. Last of all, many capillaries surround the alveoli so that the gases can move between them and the hollow sacs more readily.

This system contains many other specialised tissues and organs that improve the overall efficiency of its function. For example, rings of cartilage keep the larger airways like the trachea (25mm diameter) and bronchi (20mm diameter) open, stopping them from collapsing on themselves. However, the smaller parts like the bronchioles don’t contain cartilage so are supported by elastic fibres connecting them to surrounding lung tissue. All of these sections have smooth muscle, which allows them to open and close slightly as the muscle contracts and relaxes.

As we all know, Covid-19 is a virus and like all other viruses, it enters healthy cells in the body infecting them and creating copies of itself, quickly multiplying throughout the whole body. Covid-19 has spiky surface proteins that will easily latch onto healthy cells in our body, particularly in the lungs. Once infected, you may experience symptoms similar to that of a common cold, but as this virus reaches deeper into your respiratory system the lungs become inflamed, making it difficult to breathe. In serious cases, this can develop into a more serious condition, called pneumonia which is the infection of the alveoli.

This virus attacks a fundamental structure, essential for all human life – the respiratory system; which serves to explain the catastrophic consequences it sometimes has.


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