The Respiratory System



The same laryngotracheal groove which develops in humans to form the larynx, trachea, and lungs also develops in fishes to become the the air bladder. The air bladder is even called a lung in the lungfish, even though it is not significantly different from the air bladder of other bony fishes.

Various species of bony fishes may use the air bladder either as a respiratory "lung", as a bouyancy apparatus, as a sound reception amplifier, as a noise production amplifier, or as as some combination of these.

The several species of the family Polypteridae from Africa, are good representatives of the basic bilateral air bladder. The air bladder on the right side of the polypterid is typically larger than the left. Lungfishes also have a pair of air sacs in some species, but they are both shifted to the same side of the body.

In most higher fish species only one air sac develops. In physostomous fish the air bladder remains connected to the gut by a membranous air passage. The connection of the air passage to the gut may be placed ventrally, dorsally, or on the side of the gut tube. Some of these species can gulp air from the surface of the water and pass air into the air bladder.



In physoclistous fish the air bladder separates from the gut tube as it develops. Those species which use the air bladder as a bouyancy device have a special vascular structure in the air bladder wall, the red gland, which can concentrate blood gasses and increase the diffusion of gasses into the air bladder.



















Overview of Respiratory System

Human Nasal Passages

Human Pharynx Regions

Human Larynx and Trachea

Human Bronchi and Lungs

Muscles of Human Respiration

Lower Respiratory Development

Fish Lungs/Air Bladders

Tetrapod Lungs

Lung Ventilation Systems

Gills of Vertebrate Animals

Things I Should Know