key concept 48.3 Humans Have Tidal Respiration

The respiratory exchange surfaces in mammalian lungs are the very thin-walled alveoli that cluster around a huge number of finely branching terminal airways. To understand how these respiratory surfaces are ventilated and perfused, we will first examine the functional anatomy of the whole respiratory system (Focus: Key Figure 48.10).

focus: key figure

image
Figure 48.10 The Human Respiratory System The diagrams trace the hierarchy of human respiratory structures, from the airways to the minuscule alveoli.

Question

Q: If the trachea branches into two bronchi, each of those bronchi branches into two smaller airways, and so forth for 23 branchings, how many terminal airways are there?

If there are 23 branchings of the airways, each giving rise to 2 new branches, the total number of terminal airways would be 223, or 8,388,608.

Activity 48.1 The Human Respiratory System

www.life11e.com/ac48.1

focus your learning

  • Mucus traps particulates in the inhaled air and surfactants decrease the work of ventilation.

  • Inhalation and exhalation of air result from changes in the volume and the pressure in the thoracic cavity.