Chapter 4: Lungs and lung disease

Structure of the human gas-exchange system

The volume of oxygen that has to be absorbed and the volume of carbon dioxide that must be removed are large in mammals because:

• they are large organisms with a large volume of living cells,
• they maintain a high body temperature and so have high metabolic and respiratory rates.

The lungs are located inside the body because:

• are is not dense enough to support and protect these delicate structures,
• they would otherwise lose a great deal of water and dry out.

The main parts of the human gas-exchange system and their structure and functions:

• The lungs are a pair of lobed structures made up of a series of highly brnched tubules, called bronchioles, which end in tiny air sacs called alveoli.

• The trachea is a flexible airway that is supported by rings of cartilage. The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing…