How we Breathe~The Bell Jar model

How do we breathe?

Clara and Dominic have both produced a statement, upon how the bell jar represents the way we breathe, our respiratory system. Clara states that the model is correct as it shows that we breathe because the diaphragm moves up and down, on the contrary Dominic says the model is incorrect as we breathe with our ribs. My conclusion on who is correct is that Clara is correct because the diaphragm does move up and down when we breathe, however, Dominic, in a sense, is also correct as Well, as the diaphragm muscle is attached to the base of the ribs - especially during 'forced' exhalation - the diaphragm muscle uses the ribs as a bridge in forcing the air quickly from the body, when necessary. During inhalation, the intercostal muscles that attach between ribs - from rib to rib - allow that the rib cage expands which assists the lungs to more efficiently do their job of taking air in. Of course, a major function of the ribs is to protect vital internal organs - such as heart and lungs from outside forces.
The Act of Breathing
Breathing starts at the nose and mouth. You inhale air into your nose or mouth, and it travels down the back of your throat and into your windpipe, or trachea. Your trachea then divides into air passages called bronchial tubes. For your lungs to perform their best, these airways need to be open during inhalation and exhalation and free from inflammation or swelling and excess or abnormal amounts of mucus. As the bronchial tubes pass through the lungs, they divide into smaller air passages called bronchioles. The bronchioles end in tiny balloon-like air sacs called alveoli. Your body has over 300 million alveoli. The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Oxygen from the inhaled air passes through the alveoli walls and into the blood. After absorbing oxygen, the blood leaves the lungs and is carried to your heart. Your heart then pumps it through your body to provide oxygen to the cells of your tissues and organs. As the cells use the oxygen, carbon dioxide is produced and absorbed into the blood. Your blood then carries the carbon dioxide back to your lungs through the capillaries, where it is removed from the body when you exhale.
Demonstration of Breathing Mechanism using the Bell Jar

Take a bell jar. Towards its rounded end, fix a 'Y' shaped glass tube and on the open ends of the two branches tie a balloon each. On its open end tie a thin rubber sheet. The cavity of the bell jar acts as the thoracic cavity, the "Y" shaped tube as the trachea that branches into bronchi and the rubber sheet as the diaphragm.

Experiment Demonstrating Breathing
To demonstrate breathing, pull the rubber sheet down. The balloons get inflated. This shows how the lungs are filled with air when the diaphragm moves down. This shows that we use our diaphragm to breathe, as it moves up and down allowing our lungs to receive air, proving Clara’s statement to be correct! Due to this, I can be fully sure that Clara is fully correct!
Why it was hard for early scientists to state how we breathe
However, scientists couldn’t always have known this, meaning it was a discovery but it wasn’t until there was more technology they could’ve figured it out. Scientists struggled to be able to make progress with their knowledge as there was not much technology and due to the fact that not much else was being invented at the time to prove or test theories.
The principle behind the bell jar
The physical principle behind this, of course, is that known as Boyle's law, which states that at constant temperature, for a fixed amount of gas, pressure and volume are inversely proportional, or PV=k. In other words, if you squeeze a container of gas, lowering its volume, the pressure of the gas will rise, and when you increase the volume of the container, the pressure of the gas will decrease. When the diaphragm is relaxed, the pressure inside the bell jar equals the pressure outside, and the “lungs” are flaccid. When you pull down on the diaphragm, you increase the volume of the bell jar, thus lowering the pressure. Air is then forced into the “lungs” from outside, lowering the volume in the bell jar (and stretching the balloons) until the pressures inside and outside the bell jar are equal. When you push up on the diaphragm, you lower the volume in the bell jar, increasing the pressure and forcing the air out of the balloons until they collapse.
The Strengths and Weaknesses of the bell jar
Weaknesses
The diaphragm in bell jar model is pulled down during inhalation, whereas in actual respiration, the diaphragm is flattened. The wall of the bell jar is rigid, whereas the thoracic wall is flexible and changes during breathing. The bell jar cavity is filled with air, whereas the thoracic wall is filled with body fluid
Strengths
It demonstrates the function of the organs and what goes on when you breathe; the demonstrator’s hand performs the function of the abdominal muscles (or thoracic muscles), and the balloons, of course, are the lungs. With the diaphragm relaxed, the balloons are flaccid. When one pushes up on the diaphragm, the balloons deflate completely, and when one pulls down on the diaphragm, they inflate.