The Path of Airflow in Humans Help (page 2)

By — McGraw-Hill Professional
Updated on Aug 30, 2011

The Lower Respiratory Pathway

As the trachea branches, the lower respiratory pathway is created. The right and left primary bronchi ( BRAHN -kigh), the first branches, then enter the two lungs. The primary bronchi just keep branching. Eventually, a set of bronchioles ( BRAHN -kee- ohls ) or “little bronchi” emerges. Much like an inverted (upside down) tree, the respiratory tree thus consists of a succession of ever-smaller and more numerous branches – the larynx, trachea, bronchi, and bronchioles.

At the furthest tips of the bronchioles, hang clusters of thousands of alveoli. (Picture the many olives suspended from the branches of an inverted olive tree.) Each alveolus is essentially a collapsible, extremely thin-walled air sac. It is across the walls of the alveoli, and their close neighbors, the pulmonary capillaries, that external respiration occurs. By this means, remember, oxygen contained in the inhaled air finally enters the bloodstream.

[ Study suggestion: Look very carefully at Figure 18.3. Which structure mentioned in this section do you think represents the so-called “Adam’s apple” in males? Why?]

The Respiratory System: Breath of Life The Path of Airflow in Humans The Lower Respiratory Pathway

Fig. 18.3 The respiratory tree.

Practice problems for these concepts can be found at:  The Respiratory System Test

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