The Respiratory System
When you run up the stairs at the Metro station, your breathing speeds up without you deciding it. Every day you breathe about twenty thousand times. That air follows a specific path to the only place in the body where oxygen can pass into the blood and carbon dioxide can be picked up. What is that path, and how does air move through it?
The airways: the path of the air
If you take a deep breath through your nose on a cold early morning in Toluca, you feel the cold at the start of your nose, but by the time the air reaches your chest it is already warm and moist. What passages does that air go through, and how is it prepared before it reaches the lungs?
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…
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…
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.
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…
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.
Gas exchange in the alveoli
The air you inhale contains 21% oxygen and barely 0.04% carbon dioxide. The air you exhale leaves with 16% oxygen and 4% carbon dioxide. In what microscopic structure and through what process does this transfer of gases with the blood take place?
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.
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.
Breathing movements
When the chest expands, the pressure inside the lungs drops and air from outside rushes in to equalize it. When the chest gets smaller, the pressure rises and the air leaves.
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…
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.
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.…
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…
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.
Breathing and health
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.…
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…
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."
- 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.
- 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.
Back to the beginning: when you climb the Metro stairs, your body needs more oxygen, so the diaphragm and the ribs move faster and with a wider range. The air travels through the airways to the alveoli, where it passes into the blood.