Gas Exchange:

This takes place in the tiny air sacs in the lungs called alveoli .
Oxygen from the inhaled air diffuses through the thin walls of the alveoli into the blood in the surrounding capillaries, where it binds to hemoglobin in red blood cells.
At the same time, carbon dioxide, a waste product of cellular respiration, diffuses from the blood into the alveoli to be exhaled.

Key Points:

Purpose of Breathing: To supply oxygen to the body’s cells for energy production (via aerobic respiration) and to remove carbon dioxide, a waste product.

Respiratory System Organs Involved: Nose/mouth, trachea, bronchi, bronchioles, and lungs (especially alveoli).

Diaphragm and Intercostal Muscles: These are essential for the mechanics of breathing.