THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The respiratory system takes up oxygen from the air we breathe and expels the unwanted carbon dioxide. The main organ of the respiratory system is the lungs. Other respiratory organs include the nose, the trachea and the breathing muscles (the diaphragm and the intercostal muscles).

Detailed explanation-2: -Gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them. As shown below, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli.