Penguins have lungs, too. But these lungs aren't like ours at all. You're probably familiar with our system of lungs: we have two and air is conducted in when we inhale and out when we exhale. These means that mammal lungs have blind ends. Air goes in, stops, and comes right back out. In penguin lungs, air never stops. Find out why below.

Respiratory System

    Early in development, the respiratory system begins as a diverticulum, that is, an outpocketing, of the digestive tract. Shortly after budding outward, the digestive tract and the respiratory tract separate. The respiratory diverticulum forms two lung buds. At this point, human and penguin lung development are quite similar. Shortly after this point, penguin lung development becomes very different. Penguins develop additional organs called air sacs.

    Penguins have to breathe air just like mammals; therefore, they have to come above water while swimming. Breathing begins with inspiration. Air enters the nares, the same thing as nostrils, or oral cavity (mouth). A short distance away from this site, air travels to the lungs through the trachea or wind pipe. Penguin tracheas are much like human tracheas. The penguin trachea is composed of mucous tissue, muscle, and cartilage, just like a human trachea. Here is what the penguin trachea looks like under the microscope:

    To see a labeled trachea, click here. (Please close window when finished.)

    The very top of the image is the lumen or tunnel portion of the trachea. Right below the lumen is the respiratory epithelium. It's amazing to think that the epithelium is only one cell thick! Beneath that is some tissue and a thin layer of muscle. Dominating the image are two layers, or rings, of cartilage. Cartilage is tough tissue that sometimes forms bone.

    As air moves further down the trachea, it goes in two directions into the two lungs of the penguin. With this flow of air is a large volume of oxygen. In order to get oxygen into the blood, oxygen has to come within a very small distance of the penguin blood cells. This is when oxygenated air enters the parabronchus. The parabronchus is a specialized lung tissue found in penguins that isn't found in mammals. That's because air continually cycles through penguin lungs and air sacs. Oxygen passes along the cell surface of the parabronchus and diffuses into the tissues and then into the blood. At this point, carbon dioxide leaves the blood and enters the airspace of the parabronchus. Here's a picture of a penguin parabronchus:

    This is how blood gets oxygenated in penguins. If you look at the last picture in this section, you can see a basic model of how air flows through the penguin respiratory system. It's similar, yet different, to our very own respiratory system.