In this chapter... The lungs are one of our major organs of exchange. Like all other cells in the body, their job is to be selective about what enters and leaves through their membranes. We will spend a lot of our time looking at the chemistry and structure of cell membranes to discover how they work. The concepts of pH (acids and bases) along with flow-down gradients will also be explored. Finally, we will use pedigrees to track traits like cystic fibrosis through family trees.

The main job of the respiratory system is to exchange gasses between the air and the body. Unlike the skin, which is a barrier to the air around us, the lungs bring air in and extract oxygen so it can enter the blood. This requires a delicate balance between allowing free exchange of gasses and blocking harmful substances.

Diagram of respiratory system. Major organs. Also closeup of alveoli, or air sacs, surrounded by capillaries.

FIGURE 4-1. Anatomy of the respiratory system. ( "Respiratory system" by U.S. National Institute of Health is in the Public Domain, CC0)

Why this is important…This is one of our “vital systems” because if it stops working, death follows within minutes. Our cells need oxygen to function and the lungs provide it.

Details

The respiratory system performs several key functions in the body:

Exchange oxygen (O₂) and carbon dioxide (CO₂) between air and blood
Keep blood from becoming too acidic by expelling CO₂
Produce speech and other vocalizations (singing, laughing, etc.)

At the core of all these functions is the movement of air, which must be constantly moved in and out of the lungs. The movement of air is supported by the following organs:

Nose and nasal passages – air enters here and is warmed and humidified
Larynx – holds our vocal cords as well as a flap (epiglottis) that prevents food or fluid from entering the lungs when we swallow
Trachea – main airway moving air down the neck into the lungs
Bronchii and bronchioles – branching airways within the lungs
Lungs – site of air exchange where many small air sacs are surrounded by blood vessels
Diaphragm – main “breathing muscle”; when it contracts it creates suction in the lungs to inhale

Learning objectives

Name or identify the major organs of the respiratory system
Describe the basic functions of the respiratory system