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While other species of fish can breathe air using modified, vascularized gas bladders, [6] these bladders are usually simple sacs, devoid of complex internal structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air sacs, maximizing the surface area available for gas exchange .
A distinctive characteristic of the Australian lungfish is the presence of a single dorsal lung, used to supplement the oxygen supply through the gills. [9] During times of excessive activity, drought, or high temperatures (when water becomes deoxygenated), or when prevailing conditions inhibit normal functioning of the gills, the lungfish can ...
The dentinal tubules extend from the dentinoenamel junction (DEJ) in the crown area, or dentinocemental junction (DCJ) in the root area, to the outer wall of the pulp. [9] From the outer surface of the dentin to the area nearest the pulp, these tubules follow an S-shaped path. The diameter and density of the tubules are greatest near the pulp.
The gills of most teleost fish help to eliminate ammonia from the body, and fish live surrounded by water, but most still have a distinct bladder for storing waste fluid. The urinary bladder of teleosts is permeable to water, though this is less true for freshwater dwelling species than saltwater species.
Within the lung, numerous thin-walled blood vessels allow the blood to absorb oxygen from the air that is gulped into the lung. They are obligate air breathers, with reduced gills in the adults. There are two anterior gill arches that retain gills, though they are too small to function as the sole respiratory apparatus, and may be more ...
The pulmonates have lost their gills [1] and adapted the mantle cavity into a pallial lung. The lung has a single opening on the right side, called the pneumostome, which either remains permanently open, or opens and closes as the animal breathes. The roof of the lung is highly vascularised, and it is through this surface that gas exchange occurs.
Fluid movement inside the dentinal tubules may be away from or towards the pulp. Dentine contains many thousands of microscopic tubular structures that radiate outwards from the pulp; these dentinal tubules are typically 0.5-2 micrometres in diameter. Changes in the flow of the plasma-like biological fluid present in the dentinal tubules can ...
Obligate ram ventilation is also true of some pelagic bony fish species. [67] There are a few fish that can obtain oxygen for brief periods of time from air swallowed from above the surface of the water. Thus lungfish possess one or two lungs, and the labyrinth fish have developed a special "labyrinth organ", which characterizes this suborder ...