Which of the Following Best Summarizes How We Breathe?
📘 Question:
Which of the following statements best summarizes HOW we breathe?
- A) We inhale/exhale, then volumes change, then pressures change.
- B) We inhale/exhale, then pressures change, then volumes change.
- C) Volumes change, then pressures change, then we inhale/exhale. ✅
- D) Pressures change, then volumes change, then we inhale/exhale.
✅ Correct Answer: C) Volumes change, then pressures change, then we inhale/exhale.
🔍 Explanation:
🟦 Step 1: Muscle Contraction Drives Volume Changes
- Diaphragm contracts → thoracic cavity expands
- External intercostals lift the rib cage
- Inhalation: volume ↑
- Exhalation: volume ↓
🟨 Step 2: Volume Affects Pressure (Boyle’s Law)
According to Boyle’s Law:
- ⬆️ Volume ➝ ⬇️ Pressure (Air moves in)
- ⬇️ Volume ➝ ⬆️ Pressure (Air moves out)
🟩 Step 3: Air Movement Due to Pressure Gradient
- Air moves from high to low pressure
- Inhalation: atmospheric pressure > lung pressure
- Exhalation: lung pressure > atmospheric pressure
Conclusion: The breathing process begins with muscular action that changes thoracic volume, which then alters pressure, leading to airflow into or out of the lungs.