Your lungs are the main organs that move oxygen from the air into your blood and remove carbon dioxide from your body. Every cell needs oxygen to release usable energy from food, so breathing is directly connected to movement, thinking, healing, and survival. The respiratory system works with the circulatory system because air reaches the lungs, but blood carries gases to and from body tissues.
Understanding how lungs work helps explain exercise, asthma, choking, infections, and many medical treatments.
Key Facts
- Air pathway: nose or mouth to pharynx to larynx to trachea to bronchi to bronchioles to alveoli.
- Inhalation occurs when the diaphragm contracts and moves downward, increasing chest volume and lowering lung pressure.
- Exhalation at rest occurs when the diaphragm relaxes, chest volume decreases, and air is pushed out.
- Gas exchange happens by diffusion: O2 moves from alveoli into blood, and CO2 moves from blood into alveoli.
- Pressure and volume are inversely related: P1V1 = P2V2 for a fixed amount of gas at constant temperature.
- A typical adult at rest breathes about 12 to 20 times per minute and moves about 500 mL of air per normal breath.
Vocabulary
- Alveoli
- Tiny air sacs in the lungs where oxygen enters the blood and carbon dioxide leaves the blood.
- Diaphragm
- A dome-shaped muscle below the lungs that drives most breathing by changing the volume of the chest cavity.
- Trachea
- The windpipe that carries air from the throat toward the two main bronchi.
- Bronchioles
- Small branching airways inside the lungs that deliver air to the alveoli.
- Diffusion
- The movement of particles from an area of higher concentration to an area of lower concentration.
Common Mistakes to Avoid
- Thinking lungs actively suck air in. Air moves in because the diaphragm increases chest volume and lowers pressure inside the lungs.
- Confusing breathing with gas exchange. Breathing moves air in and out, while gas exchange is the diffusion of oxygen and carbon dioxide across the alveolar walls.
- Saying oxygen turns into carbon dioxide in the lungs. Oxygen is used by body cells during cellular respiration, and carbon dioxide produced by cells is carried back to the lungs.
- Forgetting the role of blood capillaries around alveoli. Alveoli alone cannot supply the body because gases must diffuse into nearby blood vessels to be transported.
Practice Questions
- 1 A student breathes 15 times per minute and moves 500 mL of air with each breath. What is the total volume of air moved in 1 minute in liters?
- 2 A lung model has a volume of 3.0 L at a pressure of 1.0 atm. If the volume increases to 4.0 L at constant temperature, what is the new pressure?
- 3 During an asthma attack, bronchioles become narrower. Explain how this affects airflow and why exhaling can become difficult.