The respiratory system brings oxygen into the body and removes carbon dioxide. The path of air and gas exchange are regularly tested in exams.
Path of Air
Air enters through the nose, then passes through the pharynx, larynx, trachea, bronchi and finally the alveoli in the lungs.
The Lungs
- Humans have two lungs in the chest cavity.
- The right lung has three lobes; the left has two.
- The diaphragm is the muscle that helps in breathing.
Gas Exchange
The actual exchange of gases happens in tiny air sacs called alveoli. Oxygen enters the blood and carbon dioxide leaves it. The large number of alveoli gives a very high surface area for exchange.
Breathing vs Respiration
Breathing is the physical act of inhaling and exhaling. Respiration is the chemical process inside cells that releases energy from glucose. Aerobic respiration uses oxygen; anaerobic respiration does not and produces lactic acid in muscles.
Important Facts
The larynx is the voice box. The trachea (windpipe) carries air to the lungs. The respiratory pigment in humans is haemoglobin. A normal adult breathes about 12 to 16 times per minute at rest.
Quick Revision Points
- Gas exchange happens in the alveoli.
- The diaphragm helps in breathing.
- Right lung has 3 lobes, left has 2.
- Larynx is the voice box.
- Anaerobic respiration in muscles forms lactic acid.
- Trachea is the windpipe.
- Respiration releases energy from glucose.