Q1
Where does air travel first?
ANose or mouth
BDirectly to lungs
CDirectly to alveoli
DDirectly to the heart
ICSEClass 9 (ICSE)BiologyCh 14 · Topic 1
The Respiratory System
The respiratory system enables gas exchange, taking in oxygen and releasing carbon dioxide, essential for cellular respiration throughout th
Core concept
Air travels from the nose or mouth through the trachea, into the bronchi, and finally into tiny air sacs called alveoli in the lungs.
How it works
At the alveoli, oxygen diffuses into the blood while carbon dioxide diffuses out, facilitated by the alveoli's thin walls and large surface area.
Why it matters
The diaphragm, a dome-shaped muscle, contracts and relaxes to change chest cavity volume, drawing air in and pushing air out.
Key detail
Understanding the respiratory system helps us appreciate how our body obtains the oxygen needed for cellular respiration and energy production.
Exam highlight
Key diagram
Keywords worth remembering
Trending
the respiratory systemicse class 9
Most searched
ICSE class 9 the respiratory system
Quick revision
Study resources
Notes & downloads
Quick notes
• Air travels through nose/mouth, trachea, bronchi, alveoli.
• Alveoli are tiny air sacs in the lungs.
• Oxygen diffuses into blood at alveoli.
• Carbon dioxide diffuses out at alveoli.
• Thin walls and large surface area aid diffusion.
• The diaphragm contracts and relaxes.
• This changes chest cavity volume.
• This draws air in and pushes it out.