Exercises: The respiratory system

Write the path followed by an oxygen molecule from the moment it enters the nasal cavity until it reaches an alveolus in the lungs, naming in order all the structures it passes through.

Look at the image of the respiratory system. State which number points to the trachea and which points to the diaphragm, and describe the function of each of these two structures.

Explain in your own words what alveoli are and why they are the suitable site for gas exchange between air and blood to take place.

Describe what happens to the diaphragm and ribs during inhalation (inspiration) and exhalation (expiration), and explain how these movements cause air to enter and leave the lungs.

When we regularly breathe through the mouth, air reaches the lungs colder, drier, and with more particles than when we breathe through the nose. In view of the numbered structures in the image, explain what happens to the air as it passes through the nasal cavity and why breathing through the nose is recommended.

A balloon inside a bottle with an elastic bottom is a homemade model of the respiratory system: pulling the rubber sheet at the bottom causes the balloon to inflate. Explain what the balloon, the bottle, and the rubber sheet at the bottom represent, and point out a major limitation of this model compared to the real human body.

At rest, a person inhales about $0.5\ \text{L}$ of air with each breath and takes about $14$ breaths per minute. Calculate the volume of air moved in one hour. If during exercise the volume per breath rises to $2\ \text{L}$ and the rate to $30$ breaths per minute, calculate how many times greater the volume of air moved per hour is, and explain why the body needs this increase.

Over time, smokers destroy part of the walls of their alveoli (pulmonary emphysema), causing the alveoli to merge into larger cavities with less total surface area. Reasoning from how gas exchange occurs, explain why these individuals become short of breath when exercising even though their lungs still fill with air.

During dinner, a guest talks and laughs while chewing and swallowing. Suddenly, they suffer a violent coughing fit and clutch their neck. A witness states: "They choked because the epiglottis closed at the wrong time and diverted the food into the esophagus."

1. a) Refute the witness's explanation: explain the actual function of the epiglottis during swallowing, which duct it must protect, and where the food was actually diverted.
2. b) Justify why it is anatomically impossible to speak and swallow at the same time, and explain why the reflex of coughing forcefully is the respiratory system's most effective protective response in this situation.