The Respiratory System

Question 1

Path of oxygen to the heart

Answer 1

• oxygen enters the mouth or nose
• it passes through the pharynx, past the larynx and into the trachea
• it passes into one of the bronchi, then a bronchiole, and finally an alveolus
• from the alveoli, oxygen diffuses into a red blood cell in an adjacent capillary
• red blood cells carry the oxygen to the other body tissues
• carbon dioxide follows the reverse pathway

Question 2

Inhalation

Answer 2

• by contracting, the diaphragm lowers
• intercostal muscles expand the rib cage
• these increase chest volume and the lungs
• increasing lung volume decreases the air pressure in the lungs below that of the atmosphere outside
• air is pushed into the lungs by atmospheric pressure

Question 3

Exhalation

Answer 3

• relaxing the diaphragm raises it
• the rib cage contracts
• these decrease the lung volume and increase the air pressure of the lungs above that of the atmosphere
• air is pushed out of the lungs by this pressure