Comparing Gills And Lungs

How are they alike, and different? Is one more efficient than another? Gills/Lungs?HumansIn humans air travels into the mouth, or nose, and into the nasal cavity, followed by pharynx. The pharynx is where food and air cross paths. The pharynx increases the chance of choking, but also allows breathing when exercising and respiration though the mouth, if the nose is closed. Next, epiglottis opens allowing air to move into the glottis, and pass the larynx (voice box). After this air makes its way into the trachea which cleans the air with cilia. The cilia move in the trachea and remove viruses, dust, or other unwanted material by trapping it in mucus. The mucus is than moved up the trachea into the pharynx where it is sent to the digestive system.
The challenge is how to get enough oxygen to sustain life. Water contains a fraction of oxygen compared to air. Fish also use 25 percent of their energy just to breath. Fish obtain water and oxygen though their gills. In order to open their gills, fish open their mouth, causing the opercula to close, which forces the gills to open. When the gills are open water is allowed into the respiratory system. When the fish wants to close its gills it will close its mouth, which opens the opercula and closes the gills. On the outside of the gills arches, the gills are composed of filaments that are organized into lamellae. These lamellae have capillaries in them to absorb the oxygen from the water. The direction of the blood is opposite to the direction of the water (this is also called countercurrent). Blood is flowing in the opposite direction so it can absorb most of the oxygen, that is in the water. If the blood were to move with the water an equilibrium point may be reached and only half the oxygen would be absorbed. The countercurrent flow allows the fish to absorb 80 to 90 percent of oxygen in the water.

Respiration is similar in both fish and humans in a few ways. First, both humans and fish need moist air. Second, they both have capillaries on a type of air sac that absorbs oxygen by
First, Birds have syrinx and air sacs and humans do not. Birds must inhale and exhale two times to move air in and out of the body. Air moves though more chambers in a bird than a human. Birds contract muscle and move sternum to breath, and humans move diaphragm, and contract ribs and muscles to breath. Oxygen enters the circulatory system though air capillaries in birds, and alveoli in humans.

The respiratory system in humans is much more efficient than birds. Bird respiratory system is not only slower, but takes more time. By the time a human takes in and releases air two times, a bird has only done it once.

Gill or Lungs?When comparing gills and lungs, lungs are the more efficient organ. Gills can absorb 80 to 90 percent of oxygen from water, but use 25 percent of the organisms energy. This may sound like gills extract a high amount of oxygen, but when you compare water and air with the same volume, you will find that water has 3 percent of the oxygen that is in air. Compared to gills, lungs absorb 25 percent oxygen from the air. This means that lungs absorb more air than gills. Animals with lungs only use 1 to 2 percent of their energy in respiration. In conclusion lungs are more efficient than