A Frog's Lungs & How They Work
As one of the first major four-footed tetrapods to embrace land, amphibians naturally have characteristics that resemble both land-based animals and their aquatic ancestors. The fully developed lungs are one major organ of the respiratory system, but the way in which a frog breathes through its life cycle is endemic of its evolutionary history.
Other People Are Reading
-
Lungs
-
The lungs of a frog are similar to the lungs of other animals. According to biology professor John W. Kimball, they are composed of two thin-walled sacs connected to the mouth through a small opening called a glottis. Though the lungs are small, their surface area is greatly increased by a series of inner partitions embedded with vessels through which oxygen enters the blood.
Breathing
-
Frogs lack many of the structures such as chest muscles, ribs or diaphragm that other land animals use to actively support respiration. In order to breathe, air is drawn from the nostrils into the lungs by the movement of the throat, which is why it puffs out. Once the frog opens its glottis, it can raise the floor of its mouth to force the air into its lungs.
-
Skin Respiration
-
All amphibians are tethered to the water, but their lungs do not function in aquatic environments, so frogs also use their skin as a supplementary organ for gas exchange. The frog must remain moist to breathe through the skin, which is why they are so well-adapted to moist environments.
Metamorphosis
-
Tadpoles begin their lives like their fish ancestors and breathe the oxygen in the water through internal gills. Only during the radical process of metamorphosis do frogs lose their gills and develop fully formed lungs that can breathe air. The gills are not lost until after the lungs have begun developing, which ensures a smooth continuity.
Frogs Without Lungs
-
The Bornean flat-headed frog is the only known frog that does not have any lungs. Living in the Southeast Asian island of Borneo, it was discovered in 1978, but not until three decades later did scientists find that the frog lacked lungs. All of its breathing is done through its skin, which makes it appear flat.
-
References
Resources
- Photo Credit frog on a hand - black-eyed tree frog sitting on a hand image by Christophe Fouquin from Fotolia.com
