The Descent of Penguin
Posted By Erik Seedhouse on 30 January 2006
Once they have taken a breath air enters the nares (we call them nostrils) and travels to the lungs via the trachea. Penguin tracheas are much like the human trachea and are composed of mucous tissue, muscle, and cartilage as depicted in Diagram 1 below.
Diagram 1. Cross-section of a penguin trachea.
Photo credit: Encyclopedia Britannica
The light blue area at the top of the image is the lumen or tunnel portion of the trachea. Immediately below the lumen is the respiratory epithelium that is only one cell thick and beneath this is a thin layer of muscle. The two layers (rings) that are visible are cartilage.
Diagram 2. Penguin Respiratory System
Encyclopedia Britannica
The penguin's pulmonary system is represented above. Common to the human system are the trachea, two bronchi and two lungs but there are several other features that make up the penguins' pulmonary system. The easiest way to explain the advantages of the extra features of this efficient breathing equipment is to continue to follow the passage of air as it makes its way through the system.
As it passes through the trachea air runs through a distended portion known as the syrinx an extension of the trachea that enables the penguin to vocalize. The syrinx is also the site of tracheal bifurcation, each channel connecting the syrinx to a lung. However, air first entering the respiratory system immediately flows into the posterior air sacs. This sequence of events occurs during the first inhalation.
When the penguin exhales, air situated in the posterior air sacs flows into the lungs via structures called the ventrobronchi and dorsobronchi (depicted in the third diagram below). Air flows through these respiratory passageways which subdivide and interconnect with smaller bronchi called parabronchi, the site where oxygen is exchanged. Up to this point the process if fairly similar to human respiration but unlike human respiratory physiology the air doesn't stop here; it keeps flowing!
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